From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Sat, 29 Feb 2020 15:07:56 +0000 (-0800)
Subject: cmd/compile: constant fold SSA bool to int conversions
X-Git-Tag: go1.15beta1~992
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=74f898360d2ea74d885544473cc60943771b36d4;p=gostls13.git

cmd/compile: constant fold SSA bool to int conversions

Shaves off a few instructions here and there.

file                        before   after    Δ       %
go/types.s                  322118   321851   -267    -0.083%
go/internal/gcimporter.s    34937    34909    -28     -0.080%
go/internal/gccgoimporter.s 56493    56474    -19     -0.034%
cmd/compile/internal/ssa.s  3926994  3927177  +183    +0.005%
total                       18862670 18862539 -131    -0.001%

Change-Id: I724f32317b946b5138224808f85709d9c097a247
Reviewed-on: https://go-review.googlesource.com/c/go/+/221428
Reviewed-by: Keith Randall <khr@golang.org>
---

diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index f4d487176b..54c5ed646f 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -56,6 +56,7 @@
 (Cvt64Fto64  (Const64F [c])) -> (Const64  [int64(auxTo64F(c))])
 (Round32F x:(Const32F)) -> x
 (Round64F x:(Const64F)) -> x
+(CvtBoolToUint8 (ConstBool [c])) -> (Const8 [c])
 
 (Trunc16to8  (ZeroExt8to16  x)) -> x
 (Trunc32to8  (ZeroExt8to32  x)) -> x
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index c711af249c..94c2353fd9 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -68,6 +68,8 @@ func rewriteValuegeneric(v *Value) bool {
 		return rewriteValuegeneric_OpCvt64to32F(v)
 	case OpCvt64to64F:
 		return rewriteValuegeneric_OpCvt64to64F(v)
+	case OpCvtBoolToUint8:
+		return rewriteValuegeneric_OpCvtBoolToUint8(v)
 	case OpDiv16:
 		return rewriteValuegeneric_OpDiv16(v)
 	case OpDiv16u:
@@ -2981,6 +2983,21 @@ func rewriteValuegeneric_OpCvt64to64F(v *Value) bool {
 	}
 	return false
 }
+func rewriteValuegeneric_OpCvtBoolToUint8(v *Value) bool {
+	v_0 := v.Args[0]
+	// match: (CvtBoolToUint8 (ConstBool [c]))
+	// result: (Const8 [c])
+	for {
+		if v_0.Op != OpConstBool {
+			break
+		}
+		c := v_0.AuxInt
+		v.reset(OpConst8)
+		v.AuxInt = c
+		return true
+	}
+	return false
+}
 func rewriteValuegeneric_OpDiv16(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]