cmd/compile: optimize comparisons with single bit difference

Optimize comparisons with constants that only differ by 1 bit (i.e.
a power of 2). For example:

    x == 4 || x == 6 -> x|2 == 6
    x != 1 && x != 5 -> x|4 != 5

Change-Id: Ic61719e5118446d21cf15652d9da22f7d95b2a15
Reviewed-on: https://go-review.googlesource.com/c/go/+/719420
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

1 files changed, 120 insertions, 0 deletions

diff --git a/test/codegen/fuse.go b/test/codegen/fuse.go
index 4fbb03bef8..e5a28549dc 100644
--- a/test/codegen/fuse.go
+++ b/test/codegen/fuse.go
@@ -198,6 +198,126 @@ func ui4d(c <-chan uint8) {
 	}
 }
 
+// ------------------------------------ //
+// single bit difference (conjunction)  //
+// ------------------------------------ //
+
+func sisbc64(c <-chan int64) {
+	// amd64: "ORQ [$]2,"
+	// riscv64: "ORI [$]2,"
+	for x := <-c; x != 4 && x != 6; x = <-c {
+	}
+}
+
+func sisbc32(c <-chan int32) {
+	// amd64: "ORL [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x != -1 && x != -5; x = <-c {
+	}
+}
+
+func sisbc16(c <-chan int16) {
+	// amd64: "ORL [$]32,"
+	// riscv64: "ORI [$]32,"
+	for x := <-c; x != 16 && x != 48; x = <-c {
+	}
+}
+
+func sisbc8(c <-chan int8) {
+	// amd64: "ORL [$]16,"
+	// riscv64: "ORI [$]16,"
+	for x := <-c; x != -15 && x != -31; x = <-c {
+	}
+}
+
+func uisbc64(c <-chan uint64) {
+	// amd64: "ORQ [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x != 1 && x != 5; x = <-c {
+	}
+}
+
+func uisbc32(c <-chan uint32) {
+	// amd64: "ORL [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x != 2 && x != 6; x = <-c {
+	}
+}
+
+func uisbc16(c <-chan uint16) {
+	// amd64: "ORL [$]32,"
+	// riscv64: "ORI [$]32,"
+	for x := <-c; x != 16 && x != 48; x = <-c {
+	}
+}
+
+func uisbc8(c <-chan uint8) {
+	// amd64: "ORL [$]64,"
+	// riscv64: "ORI [$]64,"
+	for x := <-c; x != 64 && x != 0; x = <-c {
+	}
+}
+
+// ------------------------------------ //
+// single bit difference (disjunction)  //
+// ------------------------------------ //
+
+func sisbd64(c <-chan int64) {
+	// amd64: "ORQ [$]2,"
+	// riscv64: "ORI [$]2,"
+	for x := <-c; x == 4 || x == 6; x = <-c {
+	}
+}
+
+func sisbd32(c <-chan int32) {
+	// amd64: "ORL [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x == -1 || x == -5; x = <-c {
+	}
+}
+
+func sisbd16(c <-chan int16) {
+	// amd64: "ORL [$]32,"
+	// riscv64: "ORI [$]32,"
+	for x := <-c; x == 16 || x == 48; x = <-c {
+	}
+}
+
+func sisbd8(c <-chan int8) {
+	// amd64: "ORL [$]16,"
+	// riscv64: "ORI [$]16,"
+	for x := <-c; x == -15 || x == -31; x = <-c {
+	}
+}
+
+func uisbd64(c <-chan uint64) {
+	// amd64: "ORQ [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x == 1 || x == 5; x = <-c {
+	}
+}
+
+func uisbd32(c <-chan uint32) {
+	// amd64: "ORL [$]4,"
+	// riscv64: "ORI [$]4,"
+	for x := <-c; x == 2 || x == 6; x = <-c {
+	}
+}
+
+func uisbd16(c <-chan uint16) {
+	// amd64: "ORL [$]32,"
+	// riscv64: "ORI [$]32,"
+	for x := <-c; x == 16 || x == 48; x = <-c {
+	}
+}
+
+func uisbd8(c <-chan uint8) {
+	// amd64: "ORL [$]64,"
+	// riscv64: "ORI [$]64,"
+	for x := <-c; x == 64 || x == 0; x = <-c {
+	}
+}
+
 // -------------------------------------//
 // merge NaN checks                     //
 // ------------------------------------ //