cmd/compile: eliminate successive swaps

The code generated when storing eight bytes loaded from memory in big endian introduced two successive byte swaps that did not actually modified the data. The new rules match this specific pattern both for amd64 and for arm64, eliminating the double swap. Fixes golang#41684 Change-Id: Icb6dc20b68e4393cef4fe6a07b33aba0d18c3ff3 Reviewed-on: https://go-review.googlesource.com/c/go/+/320073 Reviewed-by: Keith Randall <[email protected]> Run-TryBot: Keith Randall <[email protected]> TryBot-Result: Go Bot <[email protected]> Trust: Daniel Martí <[email protected]> Trust: Dmitri Shuralyov <[email protected]>
jasonhargrove · Oct 9, 2021 · e1c294a · e1c294a
1 parent 74abcab
commit e1c294a
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diff --git a/src/cmd/compile/internal/ssa/gen/AMD64.rules b/src/cmd/compile/internal/ssa/gen/AMD64.rules
@@ -2217,3 +2217,5 @@
 (AND(Q|L) x (NEG(Q|L) x)) && buildcfg.GOAMD64 >= 3 => (BLSI(Q|L) x)
 (XOR(Q|L) x (ADD(Q|L)const [-1] x)) && buildcfg.GOAMD64 >= 3 => (BLSMSK(Q|L) x)
 (AND(Q|L) x (ADD(Q|L)const [-1] x)) && buildcfg.GOAMD64 >= 3 => (BLSR(Q|L) x)
+
+(BSWAP(Q|L) (BSWAP(Q|L) p)) => p
diff --git a/src/cmd/compile/internal/ssa/gen/ARM64.rules b/src/cmd/compile/internal/ssa/gen/ARM64.rules
@@ -2931,3 +2931,5 @@
  && isInlinableMemmove(dst, src, sz, config)
  && clobber(call)
  => (Move [sz] dst src mem)
+
+((REV|REVW) ((REV|REVW) p)) => p
diff --git a/src/cmd/compile/internal/ssa/rewriteAMD64.go b/src/cmd/compile/internal/ssa/rewriteAMD64.go
diff --git a/src/cmd/compile/internal/ssa/rewriteARM64.go b/src/cmd/compile/internal/ssa/rewriteARM64.go
diff --git a/test/codegen/memcombine.go b/test/codegen/memcombine.go
@@ -432,6 +432,18 @@ func store_be32(b []byte) {
  binary.BigEndian.PutUint32(b, sink32)
 }
 
+func store_be64_load(b, x *[8]byte) {
+ // arm64:-`REV`
+ // amd64:-`BSWAPQ`
+ binary.BigEndian.PutUint64(b[:], binary.BigEndian.Uint64(x[:]))
+}
+
+func store_be32_load(b, x *[8]byte) {
+ // arm64:-`REVW`
+ // amd64:-`BSWAPL`
+ binary.BigEndian.PutUint32(b[:], binary.BigEndian.Uint32(x[:]))
+}
+
 func store_be32_idx(b []byte, idx int) {
  // amd64:`BSWAPL`,-`SHR.`
  // arm64:`REVW`,`MOVW\sR[0-9]+,\s\(R[0-9]+\)\(R[0-9]+\)`,-`MOV[BH]`,-`REV16W`