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path: root/src/cmd/compile/internal/ssa/nilcheck_test.go
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-rw-r--r--src/cmd/compile/internal/ssa/nilcheck_test.go433
1 files changed, 433 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/nilcheck_test.go b/src/cmd/compile/internal/ssa/nilcheck_test.go
new file mode 100644
index 0000000000..2d1dbc6f3e
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/nilcheck_test.go
@@ -0,0 +1,433 @@
+package ssa
+
+import (
+ "strconv"
+ "testing"
+)
+
+func BenchmarkNilCheckDeep1(b *testing.B) { benchmarkNilCheckDeep(b, 1) }
+func BenchmarkNilCheckDeep10(b *testing.B) { benchmarkNilCheckDeep(b, 10) }
+func BenchmarkNilCheckDeep100(b *testing.B) { benchmarkNilCheckDeep(b, 100) }
+func BenchmarkNilCheckDeep1000(b *testing.B) { benchmarkNilCheckDeep(b, 1000) }
+func BenchmarkNilCheckDeep10000(b *testing.B) { benchmarkNilCheckDeep(b, 10000) }
+
+// benchmarkNilCheckDeep is a stress test of nilcheckelim.
+// It uses the worst possible input: A linear string of
+// nil checks, none of which can be eliminated.
+// Run with multiple depths to observe big-O behavior.
+func benchmarkNilCheckDeep(b *testing.B, depth int) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+
+ var blocs []bloc
+ blocs = append(blocs,
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto(blockn(0)),
+ ),
+ )
+ for i := 0; i < depth; i++ {
+ blocs = append(blocs,
+ Bloc(blockn(i),
+ Valu(ptrn(i), OpAddr, ptrType, 0, nil, "sb"),
+ Valu(booln(i), OpIsNonNil, TypeBool, 0, nil, ptrn(i)),
+ If(booln(i), blockn(i+1), "exit"),
+ ),
+ )
+ }
+ blocs = append(blocs,
+ Bloc(blockn(depth), Goto("exit")),
+ Bloc("exit", Exit("mem")),
+ )
+
+ c := NewConfig("amd64", DummyFrontend{b}, nil, true)
+ fun := Fun(c, "entry", blocs...)
+
+ CheckFunc(fun.f)
+ b.SetBytes(int64(depth)) // helps for eyeballing linearity
+ b.ResetTimer()
+ b.ReportAllocs()
+
+ for i := 0; i < b.N; i++ {
+ nilcheckelim(fun.f)
+ }
+}
+
+func blockn(n int) string { return "b" + strconv.Itoa(n) }
+func ptrn(n int) string { return "p" + strconv.Itoa(n) }
+func booln(n int) string { return "c" + strconv.Itoa(n) }
+
+func isNilCheck(b *Block) bool {
+ return b.Kind == BlockIf && b.Control.Op == OpIsNonNil
+}
+
+// TestNilcheckSimple verifies that a second repeated nilcheck is removed.
+func TestNilcheckSimple(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "secondCheck", "exit")),
+ Bloc("secondCheck",
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool2", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ t.Errorf("secondCheck was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckDomOrder ensures that the nil check elimination isn't dependant
+// on the order of the dominees.
+func TestNilcheckDomOrder(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "secondCheck", "exit")),
+ Bloc("exit",
+ Exit("mem")),
+ Bloc("secondCheck",
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool2", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ t.Errorf("secondCheck was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckAddr verifies that nilchecks of OpAddr constructed values are removed.
+func TestNilcheckAddr(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpAddr, ptrType, 0, nil, "sb"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["checkPtr"] && isNilCheck(b) {
+ t.Errorf("checkPtr was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckAddPtr verifies that nilchecks of OpAddPtr constructed values are removed.
+func TestNilcheckAddPtr(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("off", OpConst64, TypeInt64, 20, nil),
+ Valu("ptr1", OpAddPtr, ptrType, 0, nil, "sb", "off"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["checkPtr"] && isNilCheck(b) {
+ t.Errorf("checkPtr was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckPhi tests that nil checks of phis, for which all values are known to be
+// non-nil are removed.
+func TestNilcheckPhi(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Valu("sp", OpSP, TypeInvalid, 0, nil),
+ Valu("baddr", OpAddr, TypeBool, 0, "b", "sp"),
+ Valu("bool1", OpLoad, TypeBool, 0, nil, "baddr", "mem"),
+ If("bool1", "b1", "b2")),
+ Bloc("b1",
+ Valu("ptr1", OpAddr, ptrType, 0, nil, "sb"),
+ Goto("checkPtr")),
+ Bloc("b2",
+ Valu("ptr2", OpAddr, ptrType, 0, nil, "sb"),
+ Goto("checkPtr")),
+ // both ptr1 and ptr2 are guaranteed non-nil here
+ Bloc("checkPtr",
+ Valu("phi", OpPhi, ptrType, 0, nil, "ptr1", "ptr2"),
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "phi"),
+ If("bool2", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["checkPtr"] && isNilCheck(b) {
+ t.Errorf("checkPtr was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckKeepRemove verifies that duplicate checks of the same pointer
+// are removed, but checks of different pointers are not.
+func TestNilcheckKeepRemove(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "differentCheck", "exit")),
+ Bloc("differentCheck",
+ Valu("ptr2", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr2"),
+ If("bool2", "secondCheck", "exit")),
+ Bloc("secondCheck",
+ Valu("bool3", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool3", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ foundDifferentCheck := false
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ t.Errorf("secondCheck was not eliminated")
+ }
+ if b == fun.blocks["differentCheck"] && isNilCheck(b) {
+ foundDifferentCheck = true
+ }
+ }
+ if !foundDifferentCheck {
+ t.Errorf("removed differentCheck, but shouldn't have")
+ }
+}
+
+// TestNilcheckInFalseBranch tests that nil checks in the false branch of an nilcheck
+// block are *not* removed.
+func TestNilcheckInFalseBranch(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("bool1", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool1", "extra", "secondCheck")),
+ Bloc("secondCheck",
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool2", "extra", "thirdCheck")),
+ Bloc("thirdCheck",
+ Valu("bool3", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool3", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ foundSecondCheck := false
+ foundThirdCheck := false
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ foundSecondCheck = true
+ }
+ if b == fun.blocks["thirdCheck"] && isNilCheck(b) {
+ foundThirdCheck = true
+ }
+ }
+ if !foundSecondCheck {
+ t.Errorf("removed secondCheck, but shouldn't have [false branch]")
+ }
+ if !foundThirdCheck {
+ t.Errorf("removed thirdCheck, but shouldn't have [false branch]")
+ }
+}
+
+// TestNilcheckUser verifies that a user nil check that dominates a generated nil check
+// wil remove the generated nil check.
+func TestNilcheckUser(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("nilptr", OpConstNil, ptrType, 0, nil),
+ Valu("bool1", OpNeqPtr, TypeBool, 0, nil, "ptr1", "nilptr"),
+ If("bool1", "secondCheck", "exit")),
+ Bloc("secondCheck",
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool2", "extra", "exit")),
+ Bloc("extra",
+ Goto("exit")),
+ Bloc("exit",
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ // we need the opt here to rewrite the user nilcheck
+ opt(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ t.Errorf("secondCheck was not eliminated")
+ }
+ }
+}
+
+// TestNilcheckBug reproduces a bug in nilcheckelim found by compiling math/big
+func TestNilcheckBug(t *testing.T) {
+ ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
+ c := NewConfig("amd64", DummyFrontend{t}, nil, true)
+ fun := Fun(c, "entry",
+ Bloc("entry",
+ Valu("mem", OpInitMem, TypeMem, 0, nil),
+ Valu("sb", OpSB, TypeInvalid, 0, nil),
+ Goto("checkPtr")),
+ Bloc("checkPtr",
+ Valu("ptr1", OpLoad, ptrType, 0, nil, "sb", "mem"),
+ Valu("nilptr", OpConstNil, ptrType, 0, nil),
+ Valu("bool1", OpNeqPtr, TypeBool, 0, nil, "ptr1", "nilptr"),
+ If("bool1", "secondCheck", "couldBeNil")),
+ Bloc("couldBeNil",
+ Goto("secondCheck")),
+ Bloc("secondCheck",
+ Valu("bool2", OpIsNonNil, TypeBool, 0, nil, "ptr1"),
+ If("bool2", "extra", "exit")),
+ Bloc("extra",
+ // prevent fuse from eliminating this block
+ Valu("store", OpStore, TypeMem, 8, nil, "ptr1", "nilptr", "mem"),
+ Goto("exit")),
+ Bloc("exit",
+ Valu("phi", OpPhi, TypeMem, 0, nil, "mem", "store"),
+ Exit("mem")))
+
+ CheckFunc(fun.f)
+ // we need the opt here to rewrite the user nilcheck
+ opt(fun.f)
+ nilcheckelim(fun.f)
+
+ // clean up the removed nil check
+ fuse(fun.f)
+ deadcode(fun.f)
+
+ CheckFunc(fun.f)
+ foundSecondCheck := false
+ for _, b := range fun.f.Blocks {
+ if b == fun.blocks["secondCheck"] && isNilCheck(b) {
+ foundSecondCheck = true
+ }
+ }
+ if !foundSecondCheck {
+ t.Errorf("secondCheck was eliminated, but shouldn't have")
+ }
+}
generated by cgit v1.3-5-g45d5 (git 2.53.0) at 2026-04-17 17:20:43 +0000