cmd/compile: fix wrong optimization for eliding Not in Phi

The previous rule may move the phi value into a wrong block.
This CL make it only rewrite the phi value not the If block,
so that the phi value will stay in old block.

Fixes #56777

Change-Id: I9479a5c7f28529786968413d35b82a16181bb1f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/451496
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Wayne Zuo <wdvxdr@golangcn.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/_gen/generic.rules

@@ -961,10 +961,11 @@
 (NilCheck (GetG mem) mem) => mem
 
 (If (Not cond) yes no) => (If cond no yes)
-(If (Phi <t> nx:(Not x) ny:(Not y)) yes no) && nx.Uses == 1 && ny.Uses == 1 => (If (Phi <t> x y) no yes)
 (If (ConstBool [c]) yes no) && c => (First yes no)
 (If (ConstBool [c]) yes no) && !c => (First no yes)
 
+(Phi <t> nx:(Not x) ny:(Not y)) && nx.Uses == 1 && ny.Uses == 1 => (Not (Phi <t> x y))
+
 // Get rid of Convert ops for pointer arithmetic on unsafe.Pointer.
 (Convert (Add(64|32) (Convert ptr mem) off) mem) => (AddPtr ptr off)
 (Convert (Convert ptr mem) mem) => ptr

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

@@ -21903,6 +21903,7 @@ func rewriteValuegeneric_OpOrB(v *Value) bool {
 	return false
 }
 func rewriteValuegeneric_OpPhi(v *Value) bool {
+	b := v.Block
 	// match: (Phi (Const8 [c]) (Const8 [c]))
 	// result: (Const8 [c])
 	for {
@@ -21983,6 +21984,34 @@ func rewriteValuegeneric_OpPhi(v *Value) bool {
 		v.AuxInt = int64ToAuxInt(c)
 		return true
 	}
+	// match: (Phi <t> nx:(Not x) ny:(Not y))
+	// cond: nx.Uses == 1 && ny.Uses == 1
+	// result: (Not (Phi <t> x y))
+	for {
+		if len(v.Args) != 2 {
+			break
+		}
+		t := v.Type
+		_ = v.Args[1]
+		nx := v.Args[0]
+		if nx.Op != OpNot {
+			break
+		}
+		x := nx.Args[0]
+		ny := v.Args[1]
+		if ny.Op != OpNot {
+			break
+		}
+		y := ny.Args[0]
+		if !(nx.Uses == 1 && ny.Uses == 1) {
+			break
+		}
+		v.reset(OpNot)
+		v0 := b.NewValue0(v.Pos, OpPhi, t)
+		v0.AddArg2(x, y)
+		v.AddArg(v0)
+		return true
+	}
 	return false
 }
 func rewriteValuegeneric_OpPtrIndex(v *Value) bool {
@@ -32462,35 +32491,6 @@ func rewriteBlockgeneric(b *Block) bool {
 			b.swapSuccessors()
 			return true
 		}
-		// match: (If (Phi <t> nx:(Not x) ny:(Not y)) yes no)
-		// cond: nx.Uses == 1 && ny.Uses == 1
-		// result: (If (Phi <t> x y) no yes)
-		for b.Controls[0].Op == OpPhi {
-			v_0 := b.Controls[0]
-			if len(v_0.Args) != 2 {
-				break
-			}
-			t := v_0.Type
-			_ = v_0.Args[1]
-			nx := v_0.Args[0]
-			if nx.Op != OpNot {
-				break
-			}
-			x := nx.Args[0]
-			ny := v_0.Args[1]
-			if ny.Op != OpNot {
-				break
-			}
-			y := ny.Args[0]
-			if !(nx.Uses == 1 && ny.Uses == 1) {
-				break
-			}
-			v0 := b.NewValue0(v_0.Pos, OpPhi, t)
-			v0.AddArg2(x, y)
-			b.resetWithControl(BlockIf, v0)
-			b.swapSuccessors()
-			return true
-		}
 		// match: (If (ConstBool [c]) yes no)
 		// cond: c
 		// result: (First yes no)

test/fixedbugs/issue56777.go

@@ -0,0 +1,56 @@
+// compile
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func fn(setText []rune, negate bool) int {
+	ranges := []singleRange{}
+
+	if len(setText) > 0 {
+		fillFirst := false
+		l := len(setText)
+		if negate {
+			if setText[0] == 0 {
+				setText = setText[1:]
+			} else {
+				l++
+				fillFirst = true
+			}
+		}
+
+		if l%2 == 0 {
+			ranges = make([]singleRange, l/2)
+		} else {
+			ranges = make([]singleRange, l/2+1)
+		}
+
+		first := true
+		if fillFirst {
+			ranges[0] = singleRange{first: 0}
+			first = false
+		}
+
+		i := 0
+		for _, r := range setText {
+			if first {
+				// lower bound in a new range
+				ranges[i] = singleRange{first: r}
+				first = false
+			} else {
+				ranges[i].last = r - 1
+				i++
+				first = true
+			}
+		}
+	}
+
+	return len(ranges)
+}
+
+type singleRange struct {
+	first rune
+	last  rune
+}