cmd/compile: merge ANDconst and UBFX into UBFX on arm64

zhangfannie · zhangfannie · commit 8ab42a945aef · 2022-03-25T01:24:44.000Z
Add a new rewrite rule to merge ANDconst and UBFX into UBFX. Add test cases. Change-Id: I24d6442d0c956d7ce092c3a3858d4a3a41771670 Reviewed-on: https://go-review.googlesource.com/c/go/+/377054 Trust: Fannie Zhang <Fannie.Zhang@arm.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Run-TryBot: Cherry Mui <cherryyz@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/ssa/gen/ARM64.rules b/src/cmd/compile/internal/ssa/gen/ARM64.rules
@@ -1918,7 +1918,11 @@
 // (x & ac) >> sc
 (SRLconst [sc] (ANDconst [ac] x)) && isARM64BFMask(sc, ac, sc)
 	=> (UBFX [armBFAuxInt(sc, arm64BFWidth(ac, sc))] x)
-
+// merge ANDconst and ubfx into ubfx
+(ANDconst [c] (UBFX [bfc] x)) && isARM64BFMask(0, c, 0) =>
+	(UBFX [armBFAuxInt(bfc.getARM64BFlsb(), min(bfc.getARM64BFwidth(), arm64BFWidth(c, 0)))] x)
+(UBFX [bfc] (ANDconst [c] x)) && isARM64BFMask(0, c, 0) && bfc.getARM64BFlsb() + bfc.getARM64BFwidth() <= arm64BFWidth(c, 0) =>
+	(UBFX [bfc] x)
 // merge ubfx and zerso-extension into ubfx
 (MOVWUreg (UBFX [bfc] x)) && bfc.getARM64BFwidth() <= 32 => (UBFX [bfc] x)
 (MOVHUreg (UBFX [bfc] x)) && bfc.getARM64BFwidth() <= 16 => (UBFX [bfc] x)
diff --git a/src/cmd/compile/internal/ssa/rewriteARM64.go b/src/cmd/compile/internal/ssa/rewriteARM64.go
diff --git a/test/codegen/bitfield.go b/test/codegen/bitfield.go
@@ -321,6 +321,12 @@ func ubfx15(x uint64) bool {
 	return false
 }
 
+// merge ANDconst and ubfx into ubfx
+func ubfx16(x uint64) uint64 {
+	// arm64:"UBFX\t[$]4, R[0-9]+, [$]6",-"AND\t[$]63"
+	return ((x >> 3) & 0xfff) >> 1 & 0x3f
+}
+
 // Check that we don't emit comparisons for constant shifts.
 //go:nosplit
 func shift_no_cmp(x int) int {
