cmd/compile: shift tests, fix triple-shift rules

Add a bunch of tests for shifts.

Fix triple-shift rules to always take constant shifts as 64 bits.
(Earlier rules always promote shift amounts to 64 bits.)
Add overflow checks.

Increases generic rule coverage to 91%

Change-Id: I6b42d368d19d36ac482dbb8e0d4f67e30ad7145d
Reviewed-on: https://go-review.googlesource.com/23555
Reviewed-by: Todd Neal <todd@tneal.org>

3 files changed, 1588 insertions, 105 deletions

diff --git a/src/cmd/compile/internal/gc/shift_test.go b/src/cmd/compile/internal/gc/shift_test.go
new file mode 100644
index 0000000000..cb6be777a7
--- /dev/null
+++ b/src/cmd/compile/internal/gc/shift_test.go
@@ -0,0 +1,907 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gc
+
+import "testing"
+
+// Tests shifts of zero.
+
+//go:noinline
+func ofz64l64(n uint64) int64 {
+	var x int64
+	return x << n
+}
+
+//go:noinline
+func ofz64l32(n uint32) int64 {
+	var x int64
+	return x << n
+}
+
+//go:noinline
+func ofz64l16(n uint16) int64 {
+	var x int64
+	return x << n
+}
+
+//go:noinline
+func ofz64l8(n uint8) int64 {
+	var x int64
+	return x << n
+}
+
+//go:noinline
+func ofz64r64(n uint64) int64 {
+	var x int64
+	return x >> n
+}
+
+//go:noinline
+func ofz64r32(n uint32) int64 {
+	var x int64
+	return x >> n
+}
+
+//go:noinline
+func ofz64r16(n uint16) int64 {
+	var x int64
+	return x >> n
+}
+
+//go:noinline
+func ofz64r8(n uint8) int64 {
+	var x int64
+	return x >> n
+}
+
+//go:noinline
+func ofz64ur64(n uint64) uint64 {
+	var x uint64
+	return x >> n
+}
+
+//go:noinline
+func ofz64ur32(n uint32) uint64 {
+	var x uint64
+	return x >> n
+}
+
+//go:noinline
+func ofz64ur16(n uint16) uint64 {
+	var x uint64
+	return x >> n
+}
+
+//go:noinline
+func ofz64ur8(n uint8) uint64 {
+	var x uint64
+	return x >> n
+}
+
+//go:noinline
+func ofz32l64(n uint64) int32 {
+	var x int32
+	return x << n
+}
+
+//go:noinline
+func ofz32l32(n uint32) int32 {
+	var x int32
+	return x << n
+}
+
+//go:noinline
+func ofz32l16(n uint16) int32 {
+	var x int32
+	return x << n
+}
+
+//go:noinline
+func ofz32l8(n uint8) int32 {
+	var x int32
+	return x << n
+}
+
+//go:noinline
+func ofz32r64(n uint64) int32 {
+	var x int32
+	return x >> n
+}
+
+//go:noinline
+func ofz32r32(n uint32) int32 {
+	var x int32
+	return x >> n
+}
+
+//go:noinline
+func ofz32r16(n uint16) int32 {
+	var x int32
+	return x >> n
+}
+
+//go:noinline
+func ofz32r8(n uint8) int32 {
+	var x int32
+	return x >> n
+}
+
+//go:noinline
+func ofz32ur64(n uint64) uint32 {
+	var x uint32
+	return x >> n
+}
+
+//go:noinline
+func ofz32ur32(n uint32) uint32 {
+	var x uint32
+	return x >> n
+}
+
+//go:noinline
+func ofz32ur16(n uint16) uint32 {
+	var x uint32
+	return x >> n
+}
+
+//go:noinline
+func ofz32ur8(n uint8) uint32 {
+	var x uint32
+	return x >> n
+}
+
+//go:noinline
+func ofz16l64(n uint64) int16 {
+	var x int16
+	return x << n
+}
+
+//go:noinline
+func ofz16l32(n uint32) int16 {
+	var x int16
+	return x << n
+}
+
+//go:noinline
+func ofz16l16(n uint16) int16 {
+	var x int16
+	return x << n
+}
+
+//go:noinline
+func ofz16l8(n uint8) int16 {
+	var x int16
+	return x << n
+}
+
+//go:noinline
+func ofz16r64(n uint64) int16 {
+	var x int16
+	return x >> n
+}
+
+//go:noinline
+func ofz16r32(n uint32) int16 {
+	var x int16
+	return x >> n
+}
+
+//go:noinline
+func ofz16r16(n uint16) int16 {
+	var x int16
+	return x >> n
+}
+
+//go:noinline
+func ofz16r8(n uint8) int16 {
+	var x int16
+	return x >> n
+}
+
+//go:noinline
+func ofz16ur64(n uint64) uint16 {
+	var x uint16
+	return x >> n
+}
+
+//go:noinline
+func ofz16ur32(n uint32) uint16 {
+	var x uint16
+	return x >> n
+}
+
+//go:noinline
+func ofz16ur16(n uint16) uint16 {
+	var x uint16
+	return x >> n
+}
+
+//go:noinline
+func ofz16ur8(n uint8) uint16 {
+	var x uint16
+	return x >> n
+}
+
+//go:noinline
+func ofz8l64(n uint64) int8 {
+	var x int8
+	return x << n
+}
+
+//go:noinline
+func ofz8l32(n uint32) int8 {
+	var x int8
+	return x << n
+}
+
+//go:noinline
+func ofz8l16(n uint16) int8 {
+	var x int8
+	return x << n
+}
+
+//go:noinline
+func ofz8l8(n uint8) int8 {
+	var x int8
+	return x << n
+}
+
+//go:noinline
+func ofz8r64(n uint64) int8 {
+	var x int8
+	return x >> n
+}
+
+//go:noinline
+func ofz8r32(n uint32) int8 {
+	var x int8
+	return x >> n
+}
+
+//go:noinline
+func ofz8r16(n uint16) int8 {
+	var x int8
+	return x >> n
+}
+
+//go:noinline
+func ofz8r8(n uint8) int8 {
+	var x int8
+	return x >> n
+}
+
+//go:noinline
+func ofz8ur64(n uint64) uint8 {
+	var x uint8
+	return x >> n
+}
+
+//go:noinline
+func ofz8ur32(n uint32) uint8 {
+	var x uint8
+	return x >> n
+}
+
+//go:noinline
+func ofz8ur16(n uint16) uint8 {
+	var x uint8
+	return x >> n
+}
+
+//go:noinline
+func ofz8ur8(n uint8) uint8 {
+	var x uint8
+	return x >> n
+}
+
+func TestShiftOfZero(t *testing.T) {
+	if got := ofz64l64(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz64l32(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz64l16(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz64l8(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz64r64(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz64r32(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz64r16(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz64r8(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz64ur64(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz64ur32(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz64ur16(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz64ur8(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+
+	if got := ofz32l64(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz32l32(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz32l16(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz32l8(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz32r64(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz32r32(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz32r16(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz32r8(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz32ur64(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz32ur32(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz32ur16(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz32ur8(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+
+	if got := ofz16l64(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz16l32(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz16l16(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz16l8(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz16r64(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz16r32(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz16r16(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz16r8(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz16ur64(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz16ur32(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz16ur16(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz16ur8(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+
+	if got := ofz8l64(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz8l32(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz8l16(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz8l8(5); got != 0 {
+		t.Errorf("0<<5 == %d, want 0", got)
+	}
+	if got := ofz8r64(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz8r32(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz8r16(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz8r8(5); got != 0 {
+		t.Errorf("0>>5 == %d, want 0", got)
+	}
+	if got := ofz8ur64(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz8ur32(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz8ur16(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+	if got := ofz8ur8(5); got != 0 {
+		t.Errorf("0>>>5 == %d, want 0", got)
+	}
+}
+
+//go:noinline
+func byz64l(n int64) int64 {
+	return n << 0
+}
+
+//go:noinline
+func byz64r(n int64) int64 {
+	return n >> 0
+}
+
+//go:noinline
+func byz64ur(n uint64) uint64 {
+	return n >> 0
+}
+
+//go:noinline
+func byz32l(n int32) int32 {
+	return n << 0
+}
+
+//go:noinline
+func byz32r(n int32) int32 {
+	return n >> 0
+}
+
+//go:noinline
+func byz32ur(n uint32) uint32 {
+	return n >> 0
+}
+
+//go:noinline
+func byz16l(n int16) int16 {
+	return n << 0
+}
+
+//go:noinline
+func byz16r(n int16) int16 {
+	return n >> 0
+}
+
+//go:noinline
+func byz16ur(n uint16) uint16 {
+	return n >> 0
+}
+
+//go:noinline
+func byz8l(n int8) int8 {
+	return n << 0
+}
+
+//go:noinline
+func byz8r(n int8) int8 {
+	return n >> 0
+}
+
+//go:noinline
+func byz8ur(n uint8) uint8 {
+	return n >> 0
+}
+
+func TestShiftByZero(t *testing.T) {
+	{
+		var n int64 = 0x5555555555555555
+		if got := byz64l(n); got != n {
+			t.Errorf("%x<<0 == %x, want %x", n, got, n)
+		}
+		if got := byz64r(n); got != n {
+			t.Errorf("%x>>0 == %x, want %x", n, got, n)
+		}
+	}
+	{
+		var n uint64 = 0xaaaaaaaaaaaaaaaa
+		if got := byz64ur(n); got != n {
+			t.Errorf("%x>>>0 == %x, want %x", n, got, n)
+		}
+	}
+
+	{
+		var n int32 = 0x55555555
+		if got := byz32l(n); got != n {
+			t.Errorf("%x<<0 == %x, want %x", n, got, n)
+		}
+		if got := byz32r(n); got != n {
+			t.Errorf("%x>>0 == %x, want %x", n, got, n)
+		}
+	}
+	{
+		var n uint32 = 0xaaaaaaaa
+		if got := byz32ur(n); got != n {
+			t.Errorf("%x>>>0 == %x, want %x", n, got, n)
+		}
+	}
+
+	{
+		var n int16 = 0x5555
+		if got := byz16l(n); got != n {
+			t.Errorf("%x<<0 == %x, want %x", n, got, n)
+		}
+		if got := byz16r(n); got != n {
+			t.Errorf("%x>>0 == %x, want %x", n, got, n)
+		}
+	}
+	{
+		var n uint16 = 0xaaaa
+		if got := byz16ur(n); got != n {
+			t.Errorf("%x>>>0 == %x, want %x", n, got, n)
+		}
+	}
+
+	{
+		var n int8 = 0x55
+		if got := byz8l(n); got != n {
+			t.Errorf("%x<<0 == %x, want %x", n, got, n)
+		}
+		if got := byz8r(n); got != n {
+			t.Errorf("%x>>0 == %x, want %x", n, got, n)
+		}
+	}
+	{
+		var n uint8 = 0x55
+		if got := byz8ur(n); got != n {
+			t.Errorf("%x>>>0 == %x, want %x", n, got, n)
+		}
+	}
+}
+
+//go:noinline
+func two64l(x int64) int64 {
+	return x << 1 << 1
+}
+
+//go:noinline
+func two64r(x int64) int64 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two64ur(x uint64) uint64 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two32l(x int32) int32 {
+	return x << 1 << 1
+}
+
+//go:noinline
+func two32r(x int32) int32 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two32ur(x uint32) uint32 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two16l(x int16) int16 {
+	return x << 1 << 1
+}
+
+//go:noinline
+func two16r(x int16) int16 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two16ur(x uint16) uint16 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two8l(x int8) int8 {
+	return x << 1 << 1
+}
+
+//go:noinline
+func two8r(x int8) int8 {
+	return x >> 1 >> 1
+}
+
+//go:noinline
+func two8ur(x uint8) uint8 {
+	return x >> 1 >> 1
+}
+
+func TestShiftCombine(t *testing.T) {
+	if got, want := two64l(4), int64(16); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := two64r(64), int64(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two64ur(64), uint64(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two32l(4), int32(16); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := two32r(64), int32(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two32ur(64), uint32(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two16l(4), int16(16); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := two16r(64), int16(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two16ur(64), uint16(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two8l(4), int8(16); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := two8r(64), int8(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := two8ur(64), uint8(16); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+
+}
+
+//go:noinline
+func three64l(x int64) int64 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three64ul(x uint64) uint64 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three64r(x int64) int64 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three64ur(x uint64) uint64 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three32l(x int32) int32 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three32ul(x uint32) uint32 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three32r(x int32) int32 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three32ur(x uint32) uint32 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three16l(x int16) int16 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three16ul(x uint16) uint16 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three16r(x int16) int16 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three16ur(x uint16) uint16 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three8l(x int8) int8 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three8ul(x uint8) uint8 {
+	return x << 3 >> 1 << 2
+}
+
+//go:noinline
+func three8r(x int8) int8 {
+	return x >> 3 << 1 >> 2
+}
+
+//go:noinline
+func three8ur(x uint8) uint8 {
+	return x >> 3 << 1 >> 2
+}
+
+func TestShiftCombine3(t *testing.T) {
+	if got, want := three64l(4), int64(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three64ul(4), uint64(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three64r(64), int64(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three64ur(64), uint64(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three32l(4), int32(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three32ul(4), uint32(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three32r(64), int32(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three32ur(64), uint32(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three16l(4), int16(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three16ul(4), uint16(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three16r(64), int16(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three16ur(64), uint16(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three8l(4), int8(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three8ul(4), uint8(64); want != got {
+		t.Errorf("4<<1<<1 == %d, want %d", got, want)
+	}
+	if got, want := three8r(64), int8(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+	if got, want := three8ur(64), uint8(4); want != got {
+		t.Errorf("64>>1>>1 == %d, want %d", got, want)
+	}
+}
+
+var (
+	one64  int64  = 1
+	one64u uint64 = 1
+	one32  int32  = 1
+	one32u uint32 = 1
+	one16  int16  = 1
+	one16u uint16 = 1
+	one8   int8   = 1
+	one8u  uint8  = 1
+)
+
+func TestShiftLargeCombine(t *testing.T) {
+	var N uint64 = 0x8000000000000000
+	if one64<<N<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one64>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one64u>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32<<N<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32u>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16<<N<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16u>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8<<N<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8u>>N>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+}
+
+func TestShiftLargeCombine3(t *testing.T) {
+	var N uint64 = 0x8000000000000001
+	if one64<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one64u<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one64>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one64u>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32u<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one32u>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16u<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one16u>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8u<<N>>2<<N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+	if one8u>>N<<2>>N == 1 {
+		t.Errorf("shift overflow mishandled")
+	}
+}
diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 7460f183d7..f5d1c98a83 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -246,17 +246,53 @@
 
 // zero shifted.
 (Lsh64x64  (Const64 [0]) _) -> (Const64 [0])
+(Lsh64x32  (Const64 [0]) _) -> (Const64 [0])
+(Lsh64x16  (Const64 [0]) _) -> (Const64 [0])
+(Lsh64x8  (Const64 [0]) _) -> (Const64 [0])
 (Rsh64x64  (Const64 [0]) _) -> (Const64 [0])
+(Rsh64x32  (Const64 [0]) _) -> (Const64 [0])
+(Rsh64x16  (Const64 [0]) _) -> (Const64 [0])
+(Rsh64x8  (Const64 [0]) _) -> (Const64 [0])
 (Rsh64Ux64 (Const64 [0]) _) -> (Const64 [0])
-(Lsh32x64  (Const64 [0]) _) -> (Const32 [0])
-(Rsh32x64  (Const64 [0]) _) -> (Const32 [0])
-(Rsh32Ux64 (Const64 [0]) _) -> (Const32 [0])
-(Lsh16x64  (Const64 [0]) _) -> (Const16 [0])
-(Rsh16x64  (Const64 [0]) _) -> (Const16 [0])
-(Rsh16Ux64 (Const64 [0]) _) -> (Const16 [0])
-(Lsh8x64   (Const64 [0]) _) -> (Const8  [0])
-(Rsh8x64   (Const64 [0]) _) -> (Const8  [0])
-(Rsh8Ux64  (Const64 [0]) _) -> (Const8  [0])
+(Rsh64Ux32 (Const64 [0]) _) -> (Const64 [0])
+(Rsh64Ux16 (Const64 [0]) _) -> (Const64 [0])
+(Rsh64Ux8 (Const64 [0]) _) -> (Const64 [0])
+(Lsh32x64  (Const32 [0]) _) -> (Const32 [0])
+(Lsh32x32  (Const32 [0]) _) -> (Const32 [0])
+(Lsh32x16  (Const32 [0]) _) -> (Const32 [0])
+(Lsh32x8  (Const32 [0]) _) -> (Const32 [0])
+(Rsh32x64  (Const32 [0]) _) -> (Const32 [0])
+(Rsh32x32  (Const32 [0]) _) -> (Const32 [0])
+(Rsh32x16  (Const32 [0]) _) -> (Const32 [0])
+(Rsh32x8  (Const32 [0]) _) -> (Const32 [0])
+(Rsh32Ux64 (Const32 [0]) _) -> (Const32 [0])
+(Rsh32Ux32 (Const32 [0]) _) -> (Const32 [0])
+(Rsh32Ux16 (Const32 [0]) _) -> (Const32 [0])
+(Rsh32Ux8 (Const32 [0]) _) -> (Const32 [0])
+(Lsh16x64  (Const16 [0]) _) -> (Const16 [0])
+(Lsh16x32  (Const16 [0]) _) -> (Const16 [0])
+(Lsh16x16  (Const16 [0]) _) -> (Const16 [0])
+(Lsh16x8  (Const16 [0]) _) -> (Const16 [0])
+(Rsh16x64  (Const16 [0]) _) -> (Const16 [0])
+(Rsh16x32  (Const16 [0]) _) -> (Const16 [0])
+(Rsh16x16  (Const16 [0]) _) -> (Const16 [0])
+(Rsh16x8  (Const16 [0]) _) -> (Const16 [0])
+(Rsh16Ux64 (Const16 [0]) _) -> (Const16 [0])
+(Rsh16Ux32 (Const16 [0]) _) -> (Const16 [0])
+(Rsh16Ux16 (Const16 [0]) _) -> (Const16 [0])
+(Rsh16Ux8 (Const16 [0]) _) -> (Const16 [0])
+(Lsh8x64   (Const8 [0]) _) -> (Const8  [0])
+(Lsh8x32   (Const8 [0]) _) -> (Const8  [0])
+(Lsh8x16   (Const8 [0]) _) -> (Const8  [0])
+(Lsh8x8   (Const8 [0]) _) -> (Const8  [0])
+(Rsh8x64   (Const8 [0]) _) -> (Const8  [0])
+(Rsh8x32   (Const8 [0]) _) -> (Const8  [0])
+(Rsh8x16   (Const8 [0]) _) -> (Const8  [0])
+(Rsh8x8   (Const8 [0]) _) -> (Const8  [0])
+(Rsh8Ux64  (Const8 [0]) _) -> (Const8  [0])
+(Rsh8Ux32  (Const8 [0]) _) -> (Const8  [0])
+(Rsh8Ux16  (Const8 [0]) _) -> (Const8  [0])
+(Rsh8Ux8  (Const8 [0]) _) -> (Const8  [0])
 
 // large left shifts of all values, and right shifts of unsigned values
 (Lsh64x64  _ (Const64 [c])) && uint64(c) >= 64 -> (Const64 [0])
@@ -286,31 +322,31 @@
 
 // ((x >> c1) << c2) >> c3
 (Rsh64Ux64 (Lsh64x64 (Rsh64Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
-  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
   -> (Rsh64Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
-(Rsh32Ux64 (Lsh32x64 (Rsh32Ux64 x (Const32 [c1])) (Const32 [c2])) (Const32 [c3]))
-  && uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)
-  -> (Rsh32Ux64 x (Const32 <config.fe.TypeUInt32()> [int64(int32(c1-c2+c3))]))
-(Rsh16Ux64 (Lsh16x64 (Rsh16Ux64 x (Const16 [c1])) (Const16 [c2])) (Const16 [c3]))
-  && uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)
-  -> (Rsh16Ux64 x (Const16 <config.fe.TypeUInt16()> [int64(int16(c1-c2+c3))]))
-(Rsh8Ux64 (Lsh8x64 (Rsh8Ux64 x (Const8 [c1])) (Const8 [c2])) (Const8 [c3]))
-  && uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)
-  -> (Rsh8Ux64 x (Const8 <config.fe.TypeUInt8()> [int64(int8(c1-c2+c3))]))
+(Rsh32Ux64 (Lsh32x64 (Rsh32Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Rsh32Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
+(Rsh16Ux64 (Lsh16x64 (Rsh16Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Rsh16Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
+(Rsh8Ux64 (Lsh8x64 (Rsh8Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Rsh8Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 
 // ((x << c1) >> c2) << c3
 (Lsh64x64 (Rsh64Ux64 (Lsh64x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
-  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
   -> (Lsh64x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
-(Lsh32x64 (Rsh32Ux64 (Lsh32x64 x (Const32 [c1])) (Const32 [c2])) (Const32 [c3]))
-  && uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)
-  -> (Lsh32x64 x (Const32 <config.fe.TypeUInt32()> [int64(int32(c1-c2+c3))]))
-(Lsh16x64 (Rsh16Ux64 (Lsh16x64 x (Const16 [c1])) (Const16 [c2])) (Const16 [c3]))
-  && uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)
-  -> (Lsh16x64 x (Const16 <config.fe.TypeUInt16()> [int64(int16(c1-c2+c3))]))
-(Lsh8x64 (Rsh8Ux64 (Lsh8x64 x (Const8 [c1])) (Const8 [c2])) (Const8 [c3]))
-  && uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)
-  -> (Lsh8x64 x (Const8 <config.fe.TypeUInt8()> [int64(int8(c1-c2+c3))]))
+(Lsh32x64 (Rsh32Ux64 (Lsh32x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Lsh32x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
+(Lsh16x64 (Rsh16Ux64 (Lsh16x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Lsh16x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
+(Lsh8x64 (Rsh8Ux64 (Lsh8x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+  && uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+  -> (Lsh8x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 
 // constant comparisons
 (Eq64 (Const64 [c]) (Const64 [d])) -> (ConstBool [b2i(c == d)])
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index c702919a57..9f08b3c4eb 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -3823,6 +3823,21 @@ func rewriteValuegeneric_OpLsh16x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh16x16  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh16x32(v *Value, config *Config) bool {
@@ -3846,6 +3861,21 @@ func rewriteValuegeneric_OpLsh16x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh16x32  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh16x64(v *Value, config *Config) bool {
@@ -3886,12 +3916,12 @@ func rewriteValuegeneric_OpLsh16x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Lsh16x64  (Const64 [0]) _)
+	// match: (Lsh16x64  (Const16 [0]) _)
 	// cond:
 	// result: (Const16 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst16 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -3947,9 +3977,9 @@ func rewriteValuegeneric_OpLsh16x64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Lsh16x64 (Rsh16Ux64 (Lsh16x64 x (Const16 [c1])) (Const16 [c2])) (Const16 [c3]))
-	// cond: uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)
-	// result: (Lsh16x64 x (Const16 <config.fe.TypeUInt16()> [int64(int16(c1-c2+c3))]))
+	// match: (Lsh16x64 (Rsh16Ux64 (Lsh16x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Lsh16x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpRsh16Ux64 {
@@ -3961,27 +3991,27 @@ func rewriteValuegeneric_OpLsh16x64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst16 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst16 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst16 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpLsh16x64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst16, config.fe.TypeUInt16())
-		v0.AuxInt = int64(int16(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -4008,6 +4038,21 @@ func rewriteValuegeneric_OpLsh16x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh16x8  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh32x16(v *Value, config *Config) bool {
@@ -4031,6 +4076,21 @@ func rewriteValuegeneric_OpLsh32x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh32x16  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh32x32(v *Value, config *Config) bool {
@@ -4054,6 +4114,21 @@ func rewriteValuegeneric_OpLsh32x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh32x32  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh32x64(v *Value, config *Config) bool {
@@ -4094,12 +4169,12 @@ func rewriteValuegeneric_OpLsh32x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Lsh32x64  (Const64 [0]) _)
+	// match: (Lsh32x64  (Const32 [0]) _)
 	// cond:
 	// result: (Const32 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst32 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -4155,9 +4230,9 @@ func rewriteValuegeneric_OpLsh32x64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Lsh32x64 (Rsh32Ux64 (Lsh32x64 x (Const32 [c1])) (Const32 [c2])) (Const32 [c3]))
-	// cond: uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)
-	// result: (Lsh32x64 x (Const32 <config.fe.TypeUInt32()> [int64(int32(c1-c2+c3))]))
+	// match: (Lsh32x64 (Rsh32Ux64 (Lsh32x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Lsh32x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpRsh32Ux64 {
@@ -4169,27 +4244,27 @@ func rewriteValuegeneric_OpLsh32x64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst32 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst32 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst32 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpLsh32x64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst32, config.fe.TypeUInt32())
-		v0.AuxInt = int64(int32(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -4216,6 +4291,21 @@ func rewriteValuegeneric_OpLsh32x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh32x8  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh64x16(v *Value, config *Config) bool {
@@ -4239,6 +4329,21 @@ func rewriteValuegeneric_OpLsh64x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh64x16  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh64x32(v *Value, config *Config) bool {
@@ -4262,6 +4367,21 @@ func rewriteValuegeneric_OpLsh64x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh64x32  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh64x64(v *Value, config *Config) bool {
@@ -4364,7 +4484,7 @@ func rewriteValuegeneric_OpLsh64x64(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Lsh64x64 (Rsh64Ux64 (Lsh64x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
-	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
 	// result: (Lsh64x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
@@ -4391,7 +4511,7 @@ func rewriteValuegeneric_OpLsh64x64(v *Value, config *Config) bool {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpLsh64x64)
@@ -4424,6 +4544,21 @@ func rewriteValuegeneric_OpLsh64x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh64x8  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh8x16(v *Value, config *Config) bool {
@@ -4447,6 +4582,21 @@ func rewriteValuegeneric_OpLsh8x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh8x16   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh8x32(v *Value, config *Config) bool {
@@ -4470,6 +4620,21 @@ func rewriteValuegeneric_OpLsh8x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh8x32   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpLsh8x64(v *Value, config *Config) bool {
@@ -4510,12 +4675,12 @@ func rewriteValuegeneric_OpLsh8x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Lsh8x64   (Const64 [0]) _)
+	// match: (Lsh8x64   (Const8 [0]) _)
 	// cond:
 	// result: (Const8  [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst8 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -4571,9 +4736,9 @@ func rewriteValuegeneric_OpLsh8x64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Lsh8x64 (Rsh8Ux64 (Lsh8x64 x (Const8 [c1])) (Const8 [c2])) (Const8 [c3]))
-	// cond: uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)
-	// result: (Lsh8x64 x (Const8 <config.fe.TypeUInt8()> [int64(int8(c1-c2+c3))]))
+	// match: (Lsh8x64 (Rsh8Ux64 (Lsh8x64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Lsh8x64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpRsh8Ux64 {
@@ -4585,27 +4750,27 @@ func rewriteValuegeneric_OpLsh8x64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst8 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst8 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst8 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpLsh8x64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst8, config.fe.TypeUInt8())
-		v0.AuxInt = int64(int8(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -4632,6 +4797,21 @@ func rewriteValuegeneric_OpLsh8x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Lsh8x8   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpMod16(v *Value, config *Config) bool {
@@ -6600,6 +6780,21 @@ func rewriteValuegeneric_OpRsh16Ux16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16Ux16 (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh16Ux32(v *Value, config *Config) bool {
@@ -6623,6 +6818,21 @@ func rewriteValuegeneric_OpRsh16Ux32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16Ux32 (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh16Ux64(v *Value, config *Config) bool {
@@ -6663,12 +6873,12 @@ func rewriteValuegeneric_OpRsh16Ux64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh16Ux64 (Const64 [0]) _)
+	// match: (Rsh16Ux64 (Const16 [0]) _)
 	// cond:
 	// result: (Const16 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst16 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -6724,9 +6934,9 @@ func rewriteValuegeneric_OpRsh16Ux64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Rsh16Ux64 (Lsh16x64 (Rsh16Ux64 x (Const16 [c1])) (Const16 [c2])) (Const16 [c3]))
-	// cond: uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)
-	// result: (Rsh16Ux64 x (Const16 <config.fe.TypeUInt16()> [int64(int16(c1-c2+c3))]))
+	// match: (Rsh16Ux64 (Lsh16x64 (Rsh16Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Rsh16Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpLsh16x64 {
@@ -6738,27 +6948,27 @@ func rewriteValuegeneric_OpRsh16Ux64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst16 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst16 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst16 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint16(c1) >= uint16(c2) && uint16(c3) >= uint16(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpRsh16Ux64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst16, config.fe.TypeUInt16())
-		v0.AuxInt = int64(int16(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -6785,6 +6995,21 @@ func rewriteValuegeneric_OpRsh16Ux8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16Ux8 (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh16x16(v *Value, config *Config) bool {
@@ -6808,6 +7033,21 @@ func rewriteValuegeneric_OpRsh16x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16x16  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh16x32(v *Value, config *Config) bool {
@@ -6831,6 +7071,21 @@ func rewriteValuegeneric_OpRsh16x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16x32  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh16x64(v *Value, config *Config) bool {
@@ -6871,12 +7126,12 @@ func rewriteValuegeneric_OpRsh16x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh16x64  (Const64 [0]) _)
+	// match: (Rsh16x64  (Const16 [0]) _)
 	// cond:
 	// result: (Const16 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst16 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -6939,6 +7194,21 @@ func rewriteValuegeneric_OpRsh16x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh16x8  (Const16 [0]) _)
+	// cond:
+	// result: (Const16 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst16 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst16)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32Ux16(v *Value, config *Config) bool {
@@ -6962,6 +7232,21 @@ func rewriteValuegeneric_OpRsh32Ux16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32Ux16 (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32Ux32(v *Value, config *Config) bool {
@@ -6985,6 +7270,21 @@ func rewriteValuegeneric_OpRsh32Ux32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32Ux32 (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32Ux64(v *Value, config *Config) bool {
@@ -7025,12 +7325,12 @@ func rewriteValuegeneric_OpRsh32Ux64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh32Ux64 (Const64 [0]) _)
+	// match: (Rsh32Ux64 (Const32 [0]) _)
 	// cond:
 	// result: (Const32 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst32 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -7086,9 +7386,9 @@ func rewriteValuegeneric_OpRsh32Ux64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Rsh32Ux64 (Lsh32x64 (Rsh32Ux64 x (Const32 [c1])) (Const32 [c2])) (Const32 [c3]))
-	// cond: uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)
-	// result: (Rsh32Ux64 x (Const32 <config.fe.TypeUInt32()> [int64(int32(c1-c2+c3))]))
+	// match: (Rsh32Ux64 (Lsh32x64 (Rsh32Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Rsh32Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpLsh32x64 {
@@ -7100,27 +7400,27 @@ func rewriteValuegeneric_OpRsh32Ux64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst32 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst32 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst32 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint32(c1) >= uint32(c2) && uint32(c3) >= uint32(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpRsh32Ux64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst32, config.fe.TypeUInt32())
-		v0.AuxInt = int64(int32(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -7147,6 +7447,21 @@ func rewriteValuegeneric_OpRsh32Ux8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32Ux8 (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32x16(v *Value, config *Config) bool {
@@ -7170,6 +7485,21 @@ func rewriteValuegeneric_OpRsh32x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32x16  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32x32(v *Value, config *Config) bool {
@@ -7193,6 +7523,21 @@ func rewriteValuegeneric_OpRsh32x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32x32  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh32x64(v *Value, config *Config) bool {
@@ -7233,12 +7578,12 @@ func rewriteValuegeneric_OpRsh32x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh32x64  (Const64 [0]) _)
+	// match: (Rsh32x64  (Const32 [0]) _)
 	// cond:
 	// result: (Const32 [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst32 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -7301,6 +7646,21 @@ func rewriteValuegeneric_OpRsh32x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh32x8  (Const32 [0]) _)
+	// cond:
+	// result: (Const32 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst32 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst32)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64Ux16(v *Value, config *Config) bool {
@@ -7324,6 +7684,21 @@ func rewriteValuegeneric_OpRsh64Ux16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64Ux16 (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64Ux32(v *Value, config *Config) bool {
@@ -7347,6 +7722,21 @@ func rewriteValuegeneric_OpRsh64Ux32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64Ux32 (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64Ux64(v *Value, config *Config) bool {
@@ -7449,7 +7839,7 @@ func rewriteValuegeneric_OpRsh64Ux64(v *Value, config *Config) bool {
 		return true
 	}
 	// match: (Rsh64Ux64 (Lsh64x64 (Rsh64Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
-	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
 	// result: (Rsh64Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
@@ -7476,7 +7866,7 @@ func rewriteValuegeneric_OpRsh64Ux64(v *Value, config *Config) bool {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpRsh64Ux64)
@@ -7509,6 +7899,21 @@ func rewriteValuegeneric_OpRsh64Ux8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64Ux8 (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64x16(v *Value, config *Config) bool {
@@ -7532,6 +7937,21 @@ func rewriteValuegeneric_OpRsh64x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64x16  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64x32(v *Value, config *Config) bool {
@@ -7555,6 +7975,21 @@ func rewriteValuegeneric_OpRsh64x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64x32  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh64x64(v *Value, config *Config) bool {
@@ -7663,6 +8098,21 @@ func rewriteValuegeneric_OpRsh64x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh64x8  (Const64 [0]) _)
+	// cond:
+	// result: (Const64 [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst64 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst64)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8Ux16(v *Value, config *Config) bool {
@@ -7686,6 +8136,21 @@ func rewriteValuegeneric_OpRsh8Ux16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8Ux16  (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8Ux32(v *Value, config *Config) bool {
@@ -7709,6 +8174,21 @@ func rewriteValuegeneric_OpRsh8Ux32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8Ux32  (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8Ux64(v *Value, config *Config) bool {
@@ -7749,12 +8229,12 @@ func rewriteValuegeneric_OpRsh8Ux64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh8Ux64  (Const64 [0]) _)
+	// match: (Rsh8Ux64  (Const8 [0]) _)
 	// cond:
 	// result: (Const8  [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst8 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -7810,9 +8290,9 @@ func rewriteValuegeneric_OpRsh8Ux64(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Rsh8Ux64 (Lsh8x64 (Rsh8Ux64 x (Const8 [c1])) (Const8 [c2])) (Const8 [c3]))
-	// cond: uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)
-	// result: (Rsh8Ux64 x (Const8 <config.fe.TypeUInt8()> [int64(int8(c1-c2+c3))]))
+	// match: (Rsh8Ux64 (Lsh8x64 (Rsh8Ux64 x (Const64 [c1])) (Const64 [c2])) (Const64 [c3]))
+	// cond: uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)
+	// result: (Rsh8Ux64 x (Const64 <config.fe.TypeUInt64()> [c1-c2+c3]))
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpLsh8x64 {
@@ -7824,27 +8304,27 @@ func rewriteValuegeneric_OpRsh8Ux64(v *Value, config *Config) bool {
 		}
 		x := v_0_0.Args[0]
 		v_0_0_1 := v_0_0.Args[1]
-		if v_0_0_1.Op != OpConst8 {
+		if v_0_0_1.Op != OpConst64 {
 			break
 		}
 		c1 := v_0_0_1.AuxInt
 		v_0_1 := v_0.Args[1]
-		if v_0_1.Op != OpConst8 {
+		if v_0_1.Op != OpConst64 {
 			break
 		}
 		c2 := v_0_1.AuxInt
 		v_1 := v.Args[1]
-		if v_1.Op != OpConst8 {
+		if v_1.Op != OpConst64 {
 			break
 		}
 		c3 := v_1.AuxInt
-		if !(uint8(c1) >= uint8(c2) && uint8(c3) >= uint8(c2)) {
+		if !(uint64(c1) >= uint64(c2) && uint64(c3) >= uint64(c2) && !uaddOvf(c1-c2, c3)) {
 			break
 		}
 		v.reset(OpRsh8Ux64)
 		v.AddArg(x)
-		v0 := b.NewValue0(v.Line, OpConst8, config.fe.TypeUInt8())
-		v0.AuxInt = int64(int8(c1 - c2 + c3))
+		v0 := b.NewValue0(v.Line, OpConst64, config.fe.TypeUInt64())
+		v0.AuxInt = c1 - c2 + c3
 		v.AddArg(v0)
 		return true
 	}
@@ -7871,6 +8351,21 @@ func rewriteValuegeneric_OpRsh8Ux8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8Ux8  (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8x16(v *Value, config *Config) bool {
@@ -7894,6 +8389,21 @@ func rewriteValuegeneric_OpRsh8x16(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8x16   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8x32(v *Value, config *Config) bool {
@@ -7917,6 +8427,21 @@ func rewriteValuegeneric_OpRsh8x32(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8x32   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpRsh8x64(v *Value, config *Config) bool {
@@ -7957,12 +8482,12 @@ func rewriteValuegeneric_OpRsh8x64(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (Rsh8x64   (Const64 [0]) _)
+	// match: (Rsh8x64   (Const8 [0]) _)
 	// cond:
 	// result: (Const8  [0])
 	for {
 		v_0 := v.Args[0]
-		if v_0.Op != OpConst64 {
+		if v_0.Op != OpConst8 {
 			break
 		}
 		if v_0.AuxInt != 0 {
@@ -8025,6 +8550,21 @@ func rewriteValuegeneric_OpRsh8x8(v *Value, config *Config) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Rsh8x8   (Const8 [0]) _)
+	// cond:
+	// result: (Const8  [0])
+	for {
+		v_0 := v.Args[0]
+		if v_0.Op != OpConst8 {
+			break
+		}
+		if v_0.AuxInt != 0 {
+			break
+		}
+		v.reset(OpConst8)
+		v.AuxInt = 0
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpSliceCap(v *Value, config *Config) bool {