cmd/compile: optimize 386's math.bits.TrailingZeros16

This CL reverts CL 192097 and fixes the issue in CL 189277. Change-Id: Icd271262e1f5019a8e01c91f91c12c1261eeb02b Reviewed-on: https://go-review.googlesource.com/c/go/+/192519 Run-TryBot: Ben Shi <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Keith Randall <[email protected]>
golang · Aug 30, 2019 · 8d5197d · 8d5197d
1 parent ba068c1
commit 8d5197d
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Showing 4 changed files with 36 additions and 1 deletion.
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
@@ -3370,7 +3370,7 @@ func init() {
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz16, types.Types[TINT], args[0])
 		},
-		sys.AMD64, sys.ARM, sys.ARM64, sys.Wasm)
+		sys.AMD64, sys.I386, sys.ARM, sys.ARM64, sys.Wasm)
 	addF("math/bits", "TrailingZeros16",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			x := s.newValue1(ssa.OpZeroExt16to64, types.Types[TUINT64], args[0])

diff --git a/src/cmd/compile/internal/ssa/gen/386.rules b/src/cmd/compile/internal/ssa/gen/386.rules
@@ -66,6 +66,9 @@
 
 (Sqrt x) -> (SQRTSD x)
 
+(Ctz16 x) -> (BSFL (ORLconst <typ.UInt32> [0x10000] x))
+(Ctz16NonZero x) -> (BSFL x)
+
 // Lowering extension
 (SignExt8to16  x) -> (MOVBLSX x)
 (SignExt8to32  x) -> (MOVBLSX x)

diff --git a/src/cmd/compile/internal/ssa/rewrite386.go b/src/cmd/compile/internal/ssa/rewrite386.go
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
@@ -298,6 +298,7 @@ func TrailingZeros32(n uint32) int {
 
 func TrailingZeros16(n uint16) int {
 	// amd64:"BSFL","BTSL\\t\\$16"
+	// 386:"BSFL\t"
 	// arm:"ORR\t\\$65536","CLZ",-"MOVHU\tR"
 	// arm64:"ORR\t\\$65536","RBITW","CLZW",-"MOVHU\tR",-"RBIT\t",-"CLZ\t"
 	// s390x:"FLOGR","OR\t\\$65536"