[go] cmd/compile: fix prove to generate Const64 for 64bits slicemasks

[Jorropo (Gerrit)]

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Commit message

cmd/compile: fix prove to generate Const64 for 64bits slicemasks

Fixes #79874

Change-Id: I155b6571db5b3c3537c549eadfe87a14b7d5836a

Change diff

diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go
index 6f21432..6c991bd 100644
--- a/src/cmd/compile/internal/ssa/prove.go
+++ b/src/cmd/compile/internal/ssa/prove.go
@@ -2742,7 +2742,7 @@
 				// if x is larger than -y (y is negative), then slicemask is -1.
 				lim := ft.limits[x.ID]
 				if lim.umin > uint64(-delta) {
-					if cap.Op == OpAdd64 {
+					if cap.Type.Size() == 8 {
 						v.reset(OpConst64)
 					} else {
 						v.reset(OpConst32)
diff --git a/test/fixedbugs/issue79874.go b/test/fixedbugs/issue79874.go
new file mode 100644
index 0000000..50059ab
--- /dev/null
+++ b/test/fixedbugs/issue79874.go
@@ -0,0 +1,28 @@
+// run
+
+//go:build unix && !(386 || arm || mips || mipsle)
+
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+const l = 1 << 34
+
+//go:noinline
+func bug(s []byte) []byte {
+	if len(s) < l+8 {
+		panic("too short")
+	}
+	return s[min(l, len(s)):]
+}
+
+func main() {
+	s := make([]byte, l+8)
+	binary.LittleEndian.PutUint64(s[l:], l)
+	if v := binary.LittleEndian.Uint64(bug(s)); v != l {
+		panic(fmt.Sprintf("got %d, want %d", v, l))
+	}
+}

Change information

Files:

• M src/cmd/compile/internal/ssa/prove.go
• A test/fixedbugs/issue79874.go

Change size: S

Delta: 2 files changed, 29 insertions(+), 1 deletion(-)

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Gerrit

Gerrit-MessageType: newchange

Gerrit-Project: go

Gerrit-Branch: master

Gerrit-Change-Id: I155b6571db5b3c3537c549eadfe87a14b7d5836a

Gerrit-Change-Number: 787720

Gerrit-PatchSet: 1

Gerrit-Owner: Jorropo <jorro...@gmail.com>

Gerrit-Reviewer: Jorropo <jorro...@gmail.com>