cmd/compile: intrinsify math/bits/ReverseBytes{32|64} for 386

The BSWAPL instruction is supported in i486 and newer. https://github.com/golang/go/wiki/MinimumRequirements#386 says we support "All Pentium MMX or later". The Pentium is also referred to as i586, so that we are safe with these instructions. Change-Id: I6dea1f9d864a45bb07c8f8f35a81cfe16cca216c Reviewed-on: https://go-review.googlesource.com/c/go/+/465515 Run-TryBot: Wayne Zuo <[email protected]> Reviewed-by: Keith Randall <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Matthew Dempsky <[email protected]> Reviewed-by: Keith Randall <[email protected]>
cloudflare · Feb 8, 2023 · d7ac5d1 · d7ac5d1
1 parent abd55d8
commit d7ac5d1
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Showing 2 changed files with 6 additions and 3 deletions.
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
@@ -4000,10 +4000,10 @@ func InitTables() {
  },
  sys.ARM64, sys.PPC64)
 
- /* Use only on Power10 as the new byte reverse instructions that Power10 provide
- make it worthwhile as an intrinsic */
- brev_arch := []sys.ArchFamily{sys.AMD64, sys.ARM64, sys.ARM, sys.S390X}
+ brev_arch := []sys.ArchFamily{sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X}
  if buildcfg.GOPPC64 >= 10 {
+ // Use only on Power10 as the new byte reverse instructions that Power10 provide
+ // make it worthwhile as an intrinsic
  brev_arch = append(brev_arch, sys.PPC64)
  }
  /******** runtime/internal/sys ********/

diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
@@ -189,13 +189,15 @@ func OnesCount8(n uint8) int {
 
 func ReverseBytes(n uint) uint {
  // amd64:"BSWAPQ"
+ // 386:"BSWAPL"
  // s390x:"MOVDBR"
  // arm64:"REV"
  return bits.ReverseBytes(n)
 }
 
 func ReverseBytes64(n uint64) uint64 {
  // amd64:"BSWAPQ"
+ // 386:"BSWAPL"
  // s390x:"MOVDBR"
  // arm64:"REV"
  // ppc64x/power10: "BRD"
@@ -204,6 +206,7 @@ func ReverseBytes64(n uint64) uint64 {
 
 func ReverseBytes32(n uint32) uint32 {
  // amd64:"BSWAPL"
+ // 386:"BSWAPL"
  // s390x:"MOVWBR"
  // arm64:"REVW"
  // ppc64x/power10: "BRW"