[release-branch.go1.20] cmd/compile: on PPC64, fix sign/zero extension when masking

(ANDCCconst [y] (MOV.*reg x)) should only be merged when zero
extending. Otherwise, sign bits are lost on negative values.

(ANDCCconst [0xFF] (MOVBreg x)) should be simplified to a zero
extension of x. Likewise for the MOVHreg variant.

Fixes #61320

Change-Id: I04e4fd7dc6a826e870681f37506620d48393698b
Reviewed-on: https://go-review.googlesource.com/c/go/+/508775
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/509195
Auto-Submit: Heschi Kreinick <heschi@google.com>

3 files changed, 41 insertions, 70 deletions

diff --git a/src/cmd/compile/internal/ssa/_gen/PPC64.rules b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
index 5a68de0ca4..3aea9abd90 100644
--- a/src/cmd/compile/internal/ssa/_gen/PPC64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
@@ -581,16 +581,16 @@
 
 // small and of zero-extend => either zero-extend or small and
 (Select0 (ANDCCconst [c] y:(MOVBZreg _))) && c&0xFF == 0xFF => y
-(Select0 (ANDCCconst [0xFF] y:(MOVBreg _))) => y
+(Select0 (ANDCCconst [0xFF] (MOVBreg x))) => (MOVBZreg x)
 (Select0 (ANDCCconst [c] y:(MOVHZreg _)))  && c&0xFFFF == 0xFFFF => y
-(Select0 (ANDCCconst [0xFFFF] y:(MOVHreg _))) => y
+(Select0 (ANDCCconst [0xFFFF] (MOVHreg x))) => (MOVHZreg x)
 
 (AND (MOVDconst [c]) y:(MOVWZreg _))  && c&0xFFFFFFFF == 0xFFFFFFFF => y
 (AND (MOVDconst [0xFFFFFFFF]) y:(MOVWreg x)) => (MOVWZreg x)
 // normal case
-(Select0 (ANDCCconst [c] (MOV(B|BZ)reg x))) => (Select0 (ANDCCconst [c&0xFF] x))
-(Select0 (ANDCCconst [c] (MOV(H|HZ)reg x))) => (Select0 (ANDCCconst [c&0xFFFF] x))
-(Select0 (ANDCCconst [c] (MOV(W|WZ)reg x))) => (Select0 (ANDCCconst [c&0xFFFFFFFF] x))
+(Select0 (ANDCCconst [c] (MOVBZreg x))) => (Select0 (ANDCCconst [c&0xFF] x))
+(Select0 (ANDCCconst [c] (MOVHZreg x))) => (Select0 (ANDCCconst [c&0xFFFF] x))
+(Select0 (ANDCCconst [c] (MOVWZreg x))) => (Select0 (ANDCCconst [c&0xFFFFFFFF] x))
 
 // Eliminate unnecessary sign/zero extend following right shift
 (MOV(B|H|W)Zreg (SRWconst [c] (MOVBZreg x))) => (SRWconst [c] (MOVBZreg x))
diff --git a/src/cmd/compile/internal/ssa/rewritePPC64.go b/src/cmd/compile/internal/ssa/rewritePPC64.go
index bc593128da..b6aed2389a 100644
--- a/src/cmd/compile/internal/ssa/rewritePPC64.go
+++ b/src/cmd/compile/internal/ssa/rewritePPC64.go
@@ -15554,17 +15554,19 @@ func rewriteValuePPC64_OpSelect0(v *Value) bool {
 		v.copyOf(y)
 		return true
 	}
-	// match: (Select0 (ANDCCconst [0xFF] y:(MOVBreg _)))
-	// result: y
+	// match: (Select0 (ANDCCconst [0xFF] (MOVBreg x)))
+	// result: (MOVBZreg x)
 	for {
 		if v_0.Op != OpPPC64ANDCCconst || auxIntToInt64(v_0.AuxInt) != 0xFF {
 			break
 		}
-		y := v_0.Args[0]
-		if y.Op != OpPPC64MOVBreg {
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpPPC64MOVBreg {
 			break
 		}
-		v.copyOf(y)
+		x := v_0_0.Args[0]
+		v.reset(OpPPC64MOVBZreg)
+		v.AddArg(x)
 		return true
 	}
 	// match: (Select0 (ANDCCconst [c] y:(MOVHZreg _)))
@@ -15582,36 +15584,19 @@ func rewriteValuePPC64_OpSelect0(v *Value) bool {
 		v.copyOf(y)
 		return true
 	}
-	// match: (Select0 (ANDCCconst [0xFFFF] y:(MOVHreg _)))
-	// result: y
+	// match: (Select0 (ANDCCconst [0xFFFF] (MOVHreg x)))
+	// result: (MOVHZreg x)
 	for {
 		if v_0.Op != OpPPC64ANDCCconst || auxIntToInt64(v_0.AuxInt) != 0xFFFF {
 			break
 		}
-		y := v_0.Args[0]
-		if y.Op != OpPPC64MOVHreg {
-			break
-		}
-		v.copyOf(y)
-		return true
-	}
-	// match: (Select0 (ANDCCconst [c] (MOVBreg x)))
-	// result: (Select0 (ANDCCconst [c&0xFF] x))
-	for {
-		if v_0.Op != OpPPC64ANDCCconst {
-			break
-		}
-		c := auxIntToInt64(v_0.AuxInt)
 		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpPPC64MOVBreg {
+		if v_0_0.Op != OpPPC64MOVHreg {
 			break
 		}
 		x := v_0_0.Args[0]
-		v.reset(OpSelect0)
-		v0 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.NewTuple(typ.Int, types.TypeFlags))
-		v0.AuxInt = int64ToAuxInt(c & 0xFF)
-		v0.AddArg(x)
-		v.AddArg(v0)
+		v.reset(OpPPC64MOVHZreg)
+		v.AddArg(x)
 		return true
 	}
 	// match: (Select0 (ANDCCconst [c] (MOVBZreg x)))
@@ -15633,25 +15618,6 @@ func rewriteValuePPC64_OpSelect0(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Select0 (ANDCCconst [c] (MOVHreg x)))
-	// result: (Select0 (ANDCCconst [c&0xFFFF] x))
-	for {
-		if v_0.Op != OpPPC64ANDCCconst {
-			break
-		}
-		c := auxIntToInt64(v_0.AuxInt)
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpPPC64MOVHreg {
-			break
-		}
-		x := v_0_0.Args[0]
-		v.reset(OpSelect0)
-		v0 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.NewTuple(typ.Int, types.TypeFlags))
-		v0.AuxInt = int64ToAuxInt(c & 0xFFFF)
-		v0.AddArg(x)
-		v.AddArg(v0)
-		return true
-	}
 	// match: (Select0 (ANDCCconst [c] (MOVHZreg x)))
 	// result: (Select0 (ANDCCconst [c&0xFFFF] x))
 	for {
@@ -15671,25 +15637,6 @@ func rewriteValuePPC64_OpSelect0(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
-	// match: (Select0 (ANDCCconst [c] (MOVWreg x)))
-	// result: (Select0 (ANDCCconst [c&0xFFFFFFFF] x))
-	for {
-		if v_0.Op != OpPPC64ANDCCconst {
-			break
-		}
-		c := auxIntToInt64(v_0.AuxInt)
-		v_0_0 := v_0.Args[0]
-		if v_0_0.Op != OpPPC64MOVWreg {
-			break
-		}
-		x := v_0_0.Args[0]
-		v.reset(OpSelect0)
-		v0 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.NewTuple(typ.Int, types.TypeFlags))
-		v0.AuxInt = int64ToAuxInt(c & 0xFFFFFFFF)
-		v0.AddArg(x)
-		v.AddArg(v0)
-		return true
-	}
 	// match: (Select0 (ANDCCconst [c] (MOVWZreg x)))
 	// result: (Select0 (ANDCCconst [c&0xFFFFFFFF] x))
 	for {
diff --git a/test/codegen/bits.go b/test/codegen/bits.go
index 4f70627c25..cd413924fe 100644
--- a/test/codegen/bits.go
+++ b/test/codegen/bits.go
@@ -374,3 +374,27 @@ func foldConstOutOfRange(a uint64) uint64 {
 	// arm64: "MOVD\t[$]19088744",-"ADD\t[$]19088744"
 	return a + 0x1234568
 }
+
+// Verify sign-extended values are not zero-extended under a bit mask (#61297)
+func signextendAndMask8to64(a int8) (s, z uint64) {
+	// ppc64: "MOVB", "ANDCC\t[$]1015,"
+	// ppc64le: "MOVB", "ANDCC\t[$]1015,"
+	s = uint64(a) & 0x3F7
+	// ppc64: -"MOVB", "ANDCC\t[$]247,"
+	// ppc64le: -"MOVB", "ANDCC\t[$]247,"
+	z = uint64(uint8(a)) & 0x3F7
+	return
+
+}
+
+// Verify zero-extended values are not sign-extended under a bit mask (#61297)
+func zeroextendAndMask8to64(a int8, b int16) (x, y uint64) {
+	// ppc64: -"MOVB\t", -"ANDCC", "MOVBZ"
+	// ppc64le: -"MOVB\t", -"ANDCC", "MOVBZ"
+	x = uint64(a) & 0xFF
+	// ppc64: -"MOVH\t", -"ANDCC", "MOVHZ"
+	// ppc64le: -"MOVH\t", -"ANDCC", "MOVHZ"
+	y = uint64(b) & 0xFFFF
+	return
+
+}