From: Jorropo <jorropo.pgm@gmail.com>
Date: Sat, 26 Jul 2025 02:04:05 +0000 (+0200)
Subject: cmd/compile: cleanup SelectN rules by indexing into args
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=4569255f8ce8ee744e34e44465444d6d58d349de;p=gostls13.git

cmd/compile: cleanup SelectN rules by indexing into args

Change-Id: I7b8e8cd88c4d6d562aa25df91593d35d331ef63c
Reviewed-on: https://go-review.googlesource.com/c/go/+/690595
Reviewed-by: Mark Freeman <mark@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules
index 72d9677c5f..40966063d7 100644
--- a/src/cmd/compile/internal/ssa/_gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/_gen/generic.rules
@@ -2057,9 +2057,7 @@
 (Select1 (MakeTuple x y)) => y
 
 // for rewriting results of some late-expanded rewrites (below)
-(SelectN [0] (MakeResult x ___)) => x
-(SelectN [1] (MakeResult x y ___)) => y
-(SelectN [2] (MakeResult x y z ___)) => z
+(SelectN [n] m:(MakeResult ___)) => m.Args[n]
 
 // for late-expanded calls, recognize newobject and remove zeroing and nilchecks
 (Zero (SelectN [0] call:(StaticLECall _ _)) mem:(SelectN [1] call))
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index bdde103a1f..f36e0b270f 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -29886,34 +29886,15 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
 	b := v.Block
 	config := b.Func.Config
 	typ := &b.Func.Config.Types
-	// match: (SelectN [0] (MakeResult x ___))
-	// result: x
-	for {
-		if auxIntToInt64(v.AuxInt) != 0 || v_0.Op != OpMakeResult || len(v_0.Args) < 1 {
-			break
-		}
-		x := v_0.Args[0]
-		v.copyOf(x)
-		return true
-	}
-	// match: (SelectN [1] (MakeResult x y ___))
-	// result: y
+	// match: (SelectN [n] m:(MakeResult ___))
+	// result: m.Args[n]
 	for {
-		if auxIntToInt64(v.AuxInt) != 1 || v_0.Op != OpMakeResult || len(v_0.Args) < 2 {
-			break
-		}
-		y := v_0.Args[1]
-		v.copyOf(y)
-		return true
-	}
-	// match: (SelectN [2] (MakeResult x y z ___))
-	// result: z
-	for {
-		if auxIntToInt64(v.AuxInt) != 2 || v_0.Op != OpMakeResult || len(v_0.Args) < 3 {
+		n := auxIntToInt64(v.AuxInt)
+		m := v_0
+		if m.Op != OpMakeResult {
 			break
 		}
-		z := v_0.Args[2]
-		v.copyOf(z)
+		v.copyOf(m.Args[n])
 		return true
 	}
 	// match: (SelectN [0] call:(StaticCall {sym} sptr (Const64 [c]) mem))