[release-branch.go1.19] cmd/compile: on PPC64, fix sign/zero extension when masking

This backport required manual cleanup as go1.20 combined the
ANDCCconst and ANDconst opcodes into one. Similarly, CL 456736
introduced a suble bug by using (Select1 (ANDCCconst ...)). This
usually worked because the same rule quietly changes the type
of the newly created ANDCCconst to a tuple. This change exposed
the bug, so fix it too.

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

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

Fixes #61319

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/+/509018
Auto-Submit: Heschi Kreinick <heschi@google.com>
TryBot-Bypass: Heschi Kreinick <heschi@google.com>

3 files changed, 50 insertions, 76 deletions

diff --git a/src/cmd/compile/internal/ssa/gen/PPC64.rules b/src/cmd/compile/internal/ssa/gen/PPC64.rules
index 1ecef32f09..9b650bcb9b 100644
--- a/src/cmd/compile/internal/ssa/gen/PPC64.rules
+++ b/src/cmd/compile/internal/ssa/gen/PPC64.rules
@@ -578,9 +578,9 @@
 ((EQ|NE|LT|LE|GT|GE) (CMPconst [0] z:(XOR x y)) yes no) && z.Uses == 1 => ((EQ|NE|LT|LE|GT|GE) (XORCC x y) yes no)
 
 // Only lower after bool is lowered. It should always lower. This helps ensure the folding below happens reliably.
-(CondSelect x y bool) && flagArg(bool) == nil => (ISEL [6] x y (Select1 <types.TypeFlags> (ANDCCconst [1] bool)))
+(CondSelect x y bool) && flagArg(bool) == nil => (ISEL [6] x y (ANDCCconst [1] bool))
 // Fold any CR -> GPR -> CR transfers when applying the above rule.
-(ISEL [6] x y (Select1 (ANDCCconst [1] (ISELB [c] one cmp)))) => (ISEL [c] x y cmp)
+(ISEL [6] x y (ANDCCconst [1] (ISELB [c] one cmp))) => (ISEL [c] x y cmp)
 
 // Lowering loads
 (Load <t> ptr mem) && (is64BitInt(t) || isPtr(t)) => (MOVDload ptr mem)
@@ -750,16 +750,16 @@
 
 // small and of zero-extend => either zero-extend or small and
 (ANDconst [c] y:(MOVBZreg _)) && c&0xFF == 0xFF => y
-(ANDconst [0xFF] y:(MOVBreg _)) => y
+(ANDconst [0xFF] (MOVBreg x)) => (MOVBZreg x)
 (ANDconst [c] y:(MOVHZreg _))  && c&0xFFFF == 0xFFFF => y
-(ANDconst [0xFFFF] y:(MOVHreg _)) => y
+(ANDconst [0xFFFF] (MOVHreg x)) => (MOVHZreg x)
 
 (AND (MOVDconst [c]) y:(MOVWZreg _))  && c&0xFFFFFFFF == 0xFFFFFFFF => y
 (AND (MOVDconst [0xFFFFFFFF]) y:(MOVWreg x)) => (MOVWZreg x)
 // normal case
-(ANDconst [c] (MOV(B|BZ)reg x)) => (ANDconst [c&0xFF] x)
-(ANDconst [c] (MOV(H|HZ)reg x)) => (ANDconst [c&0xFFFF] x)
-(ANDconst [c] (MOV(W|WZ)reg x)) => (ANDconst [c&0xFFFFFFFF] x)
+(ANDconst [c] (MOVBZreg x)) => (ANDconst [c&0xFF] x)
+(ANDconst [c] (MOVHZreg x)) => (ANDconst [c&0xFFFF] x)
+(ANDconst [c] (MOVWZreg x)) => (ANDconst [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 2ade69f91b..173286de4f 100644
--- a/src/cmd/compile/internal/ssa/rewritePPC64.go
+++ b/src/cmd/compile/internal/ssa/rewritePPC64.go
@@ -1175,10 +1175,9 @@ func rewriteValuePPC64_OpCondSelect(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
 	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (CondSelect x y bool)
 	// cond: flagArg(bool) == nil
-	// result: (ISEL [6] x y (Select1 <types.TypeFlags> (ANDCCconst [1] bool)))
+	// result: (ISEL [6] x y (ANDCCconst [1] bool))
 	for {
 		x := v_0
 		y := v_1
@@ -1188,11 +1187,9 @@ func rewriteValuePPC64_OpCondSelect(v *Value) bool {
 		}
 		v.reset(OpPPC64ISEL)
 		v.AuxInt = int32ToAuxInt(6)
-		v0 := b.NewValue0(v.Pos, OpSelect1, types.TypeFlags)
-		v1 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.NewTuple(typ.Int, types.TypeFlags))
-		v1.AuxInt = int64ToAuxInt(1)
-		v1.AddArg(bool)
-		v0.AddArg(v1)
+		v0 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.TypeFlags)
+		v0.AuxInt = int64ToAuxInt(1)
+		v0.AddArg(bool)
 		v.AddArg3(x, y, v0)
 		return true
 	}
@@ -4587,17 +4584,15 @@ func rewriteValuePPC64_OpPPC64ANDconst(v *Value) bool {
 		v.copyOf(y)
 		return true
 	}
-	// match: (ANDconst [0xFF] y:(MOVBreg _))
-	// result: y
+	// match: (ANDconst [0xFF] (MOVBreg x))
+	// result: (MOVBZreg x)
 	for {
-		if auxIntToInt64(v.AuxInt) != 0xFF {
+		if auxIntToInt64(v.AuxInt) != 0xFF || v_0.Op != OpPPC64MOVBreg {
 			break
 		}
-		y := v_0
-		if y.Op != OpPPC64MOVBreg {
-			break
-		}
-		v.copyOf(y)
+		x := v_0.Args[0]
+		v.reset(OpPPC64MOVBZreg)
+		v.AddArg(x)
 		return true
 	}
 	// match: (ANDconst [c] y:(MOVHZreg _))
@@ -4612,29 +4607,14 @@ func rewriteValuePPC64_OpPPC64ANDconst(v *Value) bool {
 		v.copyOf(y)
 		return true
 	}
-	// match: (ANDconst [0xFFFF] y:(MOVHreg _))
-	// result: y
-	for {
-		if auxIntToInt64(v.AuxInt) != 0xFFFF {
-			break
-		}
-		y := v_0
-		if y.Op != OpPPC64MOVHreg {
-			break
-		}
-		v.copyOf(y)
-		return true
-	}
-	// match: (ANDconst [c] (MOVBreg x))
-	// result: (ANDconst [c&0xFF] x)
+	// match: (ANDconst [0xFFFF] (MOVHreg x))
+	// result: (MOVHZreg x)
 	for {
-		c := auxIntToInt64(v.AuxInt)
-		if v_0.Op != OpPPC64MOVBreg {
+		if auxIntToInt64(v.AuxInt) != 0xFFFF || v_0.Op != OpPPC64MOVHreg {
 			break
 		}
 		x := v_0.Args[0]
-		v.reset(OpPPC64ANDconst)
-		v.AuxInt = int64ToAuxInt(c & 0xFF)
+		v.reset(OpPPC64MOVHZreg)
 		v.AddArg(x)
 		return true
 	}
@@ -4651,19 +4631,6 @@ func rewriteValuePPC64_OpPPC64ANDconst(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (ANDconst [c] (MOVHreg x))
-	// result: (ANDconst [c&0xFFFF] x)
-	for {
-		c := auxIntToInt64(v.AuxInt)
-		if v_0.Op != OpPPC64MOVHreg {
-			break
-		}
-		x := v_0.Args[0]
-		v.reset(OpPPC64ANDconst)
-		v.AuxInt = int64ToAuxInt(c & 0xFFFF)
-		v.AddArg(x)
-		return true
-	}
 	// match: (ANDconst [c] (MOVHZreg x))
 	// result: (ANDconst [c&0xFFFF] x)
 	for {
@@ -4677,19 +4644,6 @@ func rewriteValuePPC64_OpPPC64ANDconst(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (ANDconst [c] (MOVWreg x))
-	// result: (ANDconst [c&0xFFFFFFFF] x)
-	for {
-		c := auxIntToInt64(v.AuxInt)
-		if v_0.Op != OpPPC64MOVWreg {
-			break
-		}
-		x := v_0.Args[0]
-		v.reset(OpPPC64ANDconst)
-		v.AuxInt = int64ToAuxInt(c & 0xFFFFFFFF)
-		v.AddArg(x)
-		return true
-	}
 	// match: (ANDconst [c] (MOVWZreg x))
 	// result: (ANDconst [c&0xFFFFFFFF] x)
 	for {
@@ -5934,7 +5888,7 @@ func rewriteValuePPC64_OpPPC64ISEL(v *Value) bool {
 		v.AddArg(y)
 		return true
 	}
-	// match: (ISEL [6] x y (Select1 (ANDCCconst [1] (ISELB [c] one cmp))))
+	// match: (ISEL [6] x y (ANDCCconst [1] (ISELB [c] one cmp)))
 	// result: (ISEL [c] x y cmp)
 	for {
 		if auxIntToInt32(v.AuxInt) != 6 {
@@ -5942,19 +5896,15 @@ func rewriteValuePPC64_OpPPC64ISEL(v *Value) bool {
 		}
 		x := v_0
 		y := v_1
-		if v_2.Op != OpSelect1 {
+		if v_2.Op != OpPPC64ANDCCconst || auxIntToInt64(v_2.AuxInt) != 1 {
 			break
 		}
 		v_2_0 := v_2.Args[0]
-		if v_2_0.Op != OpPPC64ANDCCconst || auxIntToInt64(v_2_0.AuxInt) != 1 {
-			break
-		}
-		v_2_0_0 := v_2_0.Args[0]
-		if v_2_0_0.Op != OpPPC64ISELB {
+		if v_2_0.Op != OpPPC64ISELB {
 			break
 		}
-		c := auxIntToInt32(v_2_0_0.AuxInt)
-		cmp := v_2_0_0.Args[1]
+		c := auxIntToInt32(v_2_0.AuxInt)
+		cmp := v_2_0.Args[1]
 		v.reset(OpPPC64ISEL)
 		v.AuxInt = int32ToAuxInt(c)
 		v.AddArg3(x, y, cmp)
diff --git a/test/codegen/bits.go b/test/codegen/bits.go
index e7826b8e65..71ed7905c9 100644
--- a/test/codegen/bits.go
+++ b/test/codegen/bits.go
@@ -363,3 +363,27 @@ func issue48467(x, y uint64) uint64 {
 	d, borrow := bits.Sub64(x, y, 0)
 	return x - d&(-borrow)
 }
+
+// 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
+
+}