From: Xiaolin Zhao <zhaoxiaolin@loongson.cn>
Date: Mon, 1 Dec 2025 06:46:23 +0000 (+0800)
Subject: cmd/compile: avoid extending when already sufficiently shifted on loong64
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=021d5ca042775537d707c6f5ae2f53f57dac243f;p=gostls13.git

cmd/compile: avoid extending when already sufficiently shifted on loong64

This reduces 744 instructions from the go toolchain binary on loong64.

	file         before      after      Δ       %
	asm          599282      599222   -60    -0.0100%
	cgo          513606      513534   -72    -0.0140%
	compile      2939250     2939146  -104   -0.0035%
	cover        564136      564056   -80    -0.0142%
	fix          895622      895546   -76    -0.0085%
	link         759460      759376   -84    -0.0111%
	preprofile   264960      264916   -44    -0.0166%
	vet          869964      869888   -76    -0.0087%
	go           1712990     1712890  -100   -0.0058%
	gofmt        346416      346368   -48    -0.0139%
	total        9465686     9464942  -744   -0.0079%

Change-Id: I32dfa7506d0458ca0b6de83b030c330cd2b82176
Reviewed-on: https://go-review.googlesource.com/c/go/+/725720
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
---

diff --git a/src/cmd/compile/internal/ssa/_gen/LOONG64.rules b/src/cmd/compile/internal/ssa/_gen/LOONG64.rules
index b15043032c..a40603e93d 100644
--- a/src/cmd/compile/internal/ssa/_gen/LOONG64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/LOONG64.rules
@@ -843,6 +843,11 @@
 
 (MOVBUreg (ANDconst [c] x)) => (ANDconst [c&0xff] x)
 
+// Avoid extending when already sufficiently shifted.
+(MOVBUreg x:(SRLconst [c] y)) && c >= 24 => x
+(MOVHUreg x:(SRLconst [c] y)) && c >= 16 => x
+(MOVWUreg x:(SRLconst [c] y)) => x
+
 // Avoid extending when already sufficiently masked.
 (MOVBreg  x:(ANDconst [c] y)) && c >= 0 && int64(int8(c)) == c => x
 (MOVHreg  x:(ANDconst [c] y)) && c >= 0 && int64(int16(c)) == c => x
diff --git a/src/cmd/compile/internal/ssa/rewriteLOONG64.go b/src/cmd/compile/internal/ssa/rewriteLOONG64.go
index 30ce419d40..37aedcbe6e 100644
--- a/src/cmd/compile/internal/ssa/rewriteLOONG64.go
+++ b/src/cmd/compile/internal/ssa/rewriteLOONG64.go
@@ -2677,6 +2677,21 @@ func rewriteValueLOONG64_OpLOONG64MOVBUreg(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (MOVBUreg x:(SRLconst [c] y))
+	// cond: c >= 24
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpLOONG64SRLconst {
+			break
+		}
+		c := auxIntToInt64(x.AuxInt)
+		if !(c >= 24) {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
 	// match: (MOVBUreg x:(ANDconst [c] y))
 	// cond: c >= 0 && int64(uint8(c)) == c
 	// result: x
@@ -4067,6 +4082,21 @@ func rewriteValueLOONG64_OpLOONG64MOVHUreg(v *Value) bool {
 		v.AuxInt = int64ToAuxInt(int64(uint16(c)))
 		return true
 	}
+	// match: (MOVHUreg x:(SRLconst [c] y))
+	// cond: c >= 16
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpLOONG64SRLconst {
+			break
+		}
+		c := auxIntToInt64(x.AuxInt)
+		if !(c >= 16) {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
 	// match: (MOVHUreg x:(ANDconst [c] y))
 	// cond: c >= 0 && int64(uint16(c)) == c
 	// result: x
@@ -5301,6 +5331,16 @@ func rewriteValueLOONG64_OpLOONG64MOVWUreg(v *Value) bool {
 		v.AuxInt = int64ToAuxInt(int64(uint32(c)))
 		return true
 	}
+	// match: (MOVWUreg x:(SRLconst [c] y))
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpLOONG64SRLconst {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
 	// match: (MOVWUreg x:(ANDconst [c] y))
 	// cond: c >= 0 && int64(uint32(c)) == c
 	// result: x