cmd/compile: fold constant comparisions into SETxxmem ops.

Fixes #22198

Change-Id: I5cb91c73069af8b16a2580d28756efd58c84b690
Reviewed-on: https://go-review.googlesource.com/69990
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -1545,6 +1545,66 @@
 (SETAE (FlagGT_ULT)) -> (MOVLconst [0])
 (SETAE (FlagGT_UGT)) -> (MOVLconst [1])
 
+(SETEQmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETEQmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETEQmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETEQmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETEQmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+
+(SETNEmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETNEmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETNEmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETNEmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETNEmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+
+(SETLmem  [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETLmem  [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETLmem  [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETLmem  [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETLmem  [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+
+(SETLEmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETLEmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETLEmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETLEmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETLEmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+
+(SETGmem  [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETGmem  [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETGmem  [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETGmem  [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETGmem  [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+
+(SETGEmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETGEmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETGEmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETGEmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETGEmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+
+(SETBmem  [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETBmem  [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETBmem  [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETBmem  [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETBmem  [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+
+(SETBEmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETBEmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETBEmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETBEmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETBEmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+
+(SETAmem  [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETAmem  [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETAmem  [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETAmem  [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETAmem  [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+
+(SETAEmem [off] {sym} ptr x:(FlagEQ)     mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETAEmem [off] {sym} ptr x:(FlagLT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETAEmem [off] {sym} ptr x:(FlagLT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+(SETAEmem [off] {sym} ptr x:(FlagGT_ULT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [0]) mem)
+(SETAEmem [off] {sym} ptr x:(FlagGT_UGT) mem) -> (MOVBstore [off] {sym} ptr (MOVLconst <x.Type> [1]) mem)
+
 // Remove redundant *const ops
 (ADDQconst [0] x) -> x
 (ADDLconst [c] x) && int32(c)==0 -> x

test/fixedbugs/issue22198.go

+// compile
+
+// Copyright 2017 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 issue22198
+
+func f(a *bool, b bool) {
+	if b {
+		return
+	}
+	c := '\n'
+	if b {
+		c = ' '
+	}
+	*a = c == '\n'
+}