cmd/compile: add race instrumentation during walkCompare

So the racy usage could be detected after re-writing "==" to
runtime.memequal call.

Updates #61204

Change-Id: Idb4ac37e55813cc87f9d16aa656fb447edf69ea1
Reviewed-on: https://go-review.googlesource.com/c/go/+/601117
Reviewed-by: Egon Elbre <egonelbre@gmail.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

2 files changed, 66 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/walk/compare.go b/src/cmd/compile/internal/walk/compare.go
index 625cfecee0..25160008ee 100644
--- a/src/cmd/compile/internal/walk/compare.go
+++ b/src/cmd/compile/internal/walk/compare.go
@@ -192,8 +192,18 @@ func walkCompare(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
 		// is handled by walkCompare.
 		fn, needsLength := reflectdata.EqFor(t)
 		call := ir.NewCallExpr(base.Pos, ir.OCALL, fn, nil)
-		call.Args.Append(typecheck.NodAddr(cmpl))
-		call.Args.Append(typecheck.NodAddr(cmpr))
+		addrCmpl := typecheck.NodAddr(cmpl)
+		addrCmpR := typecheck.NodAddr(cmpr)
+		if !types.IsNoRacePkg(types.LocalPkg) && base.Flag.Race {
+			ptrL := typecheck.Conv(typecheck.Conv(addrCmpl, types.Types[types.TUNSAFEPTR]), types.Types[types.TUINTPTR])
+			ptrR := typecheck.Conv(typecheck.Conv(addrCmpR, types.Types[types.TUNSAFEPTR]), types.Types[types.TUINTPTR])
+			raceFn := typecheck.LookupRuntime("racereadrange")
+			size := ir.NewInt(base.Pos, t.Size())
+			call.PtrInit().Append(mkcall1(raceFn, nil, init, ptrL, size))
+			call.PtrInit().Append(mkcall1(raceFn, nil, init, ptrR, size))
+		}
+		call.Args.Append(addrCmpl)
+		call.Args.Append(addrCmpR)
 		if needsLength {
 			call.Args.Append(ir.NewInt(base.Pos, t.Size()))
 		}
diff --git a/src/runtime/race/output_test.go b/src/runtime/race/output_test.go
index 0ee0f41334..0d5c9096f0 100644
--- a/src/runtime/race/output_test.go
+++ b/src/runtime/race/output_test.go
@@ -477,4 +477,58 @@ Previous write at 0x[0-9,a-f]+ by main goroutine:
       .*/main.go:10 \+0x[0-9,a-f]+
 
 `}},
+	{"non_inline_array_compare", "run", "", "atexit_sleep_ms=0", `
+package main
+
+import (
+	"math/rand/v2"
+)
+
+var x = [1024]byte{}
+
+var ch = make(chan bool)
+
+func main() {
+	started := make(chan struct{})
+	go func() {
+		close(started)
+		var y = [len(x)]byte{}
+		eq := x == y
+		ch <- eq
+	}()
+	<-started
+	x[rand.IntN(len(x))]++
+	println(<-ch)
+}
+`, []string{`==================
+WARNING: DATA RACE
+`}},
+	{"non_inline_struct_compare", "run", "", "atexit_sleep_ms=0", `
+package main
+
+import "math/rand/v2"
+
+type S struct {
+	a [1024]byte
+}
+
+var x = S{a: [1024]byte{}}
+
+var ch = make(chan bool)
+
+func main() {
+	started := make(chan struct{})
+	go func() {
+		close(started)
+		var y = S{a: [len(x.a)]byte{}}
+		eq := x == y
+		ch <- eq
+	}()
+	<-started
+	x.a[rand.IntN(len(x.a))]++
+	println(<-ch)
+}
+`, []string{`==================
+WARNING: DATA RACE
+`}},
 }