commit 68ac1f774624faf99e7f6ec6592acb50f23b7874
author Keith Randall <khr@golang.org> Thu Apr 07 10:21:35 2016 -0700
committer Keith Randall <khr@golang.org> Thu Apr 07 21:39:32 2016 +0000
tree 09f13f6e4fbefc37ba69a49a85547c33d51b7ae3
parent dfded57819dd9111afffc25360cd3e147859d354

cmd/compile: Fix constant-folding of unsigned shifts

Make sure the results of unsigned constant-folded
shifts are sign-extended into the AuxInt field.

Fixes #15175

Change-Id: I3490d1bc3d9b2e1578ed30964645508577894f58
Reviewed-on: https://go-review.googlesource.com/21586
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/ssa/rewritegeneric.go

diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index 932cb42..9b0f43c 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -6185,7 +6185,7 @@
 	_ = b
 	// match: (Rsh16Ux64 (Const16 [c]) (Const64 [d]))
 	// cond:
-	// result: (Const16 [int64(uint16(c) >> uint64(d))])
+	// result: (Const16 [int64(int16(uint16(c) >> uint64(d)))])
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst16 {
@@ -6198,7 +6198,7 @@
 		}
 		d := v_1.AuxInt
 		v.reset(OpConst16)
-		v.AuxInt = int64(uint16(c) >> uint64(d))
+		v.AuxInt = int64(int16(uint16(c) >> uint64(d)))
 		return true
 	}
 	// match: (Rsh16Ux64 (Const16 [0]) _)
@@ -6547,7 +6547,7 @@
 	_ = b
 	// match: (Rsh32Ux64 (Const32 [c]) (Const64 [d]))
 	// cond:
-	// result: (Const32 [int64(uint32(c) >> uint64(d))])
+	// result: (Const32 [int64(int32(uint32(c) >> uint64(d)))])
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst32 {
@@ -6560,7 +6560,7 @@
 		}
 		d := v_1.AuxInt
 		v.reset(OpConst32)
-		v.AuxInt = int64(uint32(c) >> uint64(d))
+		v.AuxInt = int64(int32(uint32(c) >> uint64(d)))
 		return true
 	}
 	// match: (Rsh32Ux64 (Const32 [0]) _)
@@ -7353,7 +7353,7 @@
 	_ = b
 	// match: (Rsh8Ux64  (Const8  [c]) (Const64 [d]))
 	// cond:
-	// result: (Const8  [int64(uint8(c) >> uint64(d))])
+	// result: (Const8  [int64(int8(uint8(c) >> uint64(d)))])
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst8 {
@@ -7366,7 +7366,7 @@
 		}
 		d := v_1.AuxInt
 		v.reset(OpConst8)
-		v.AuxInt = int64(uint8(c) >> uint64(d))
+		v.AuxInt = int64(int8(uint8(c) >> uint64(d)))
 		return true
 	}
 	// match: (Rsh8Ux64  (Const8  [0]) _)