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cmd/compile/internal/ssa: fix PPC64 merging of (AND (S[RL]Dconst ...)

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CL 622236 forgot to check the mask was also a 32 bit rotate mask. Add
a modified version of isPPC64WordRotateMask which valids the mask is
contiguous and fits inside a uint32.

I don't this is possible when merging SRDconst, the first check should
always reject such combines. But, be extra careful and do it there
too.

Fixes #73153

Change-Id: Ie95f74ec5e7d89dc761511126db814f886a7a435
Reviewed-on: https://go-review.googlesource.com/c/go/+/679775
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Jayanth Krishnamurthy <jayanth.krishnamurthy@ibm.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Paul Murphy 2025-06-04 08:51:11 -05:00 committed by Gopher Robot
parent 985d600f3a
commit ee7bfbdbcc
2 changed files with 27 additions and 2 deletions
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19
src/cmd/compile/internal/ssa/rewrite.go
View File

@ -1583,6 +1583,11 @@ func GetPPC64Shiftme(auxint int64) int64 {
// operation. Masks can also extend from the msb and wrap to // operation. Masks can also extend from the msb and wrap to
// the lsb too. That is, the valid masks are 32 bit strings // the lsb too. That is, the valid masks are 32 bit strings
// of the form: 0..01..10..0 or 1..10..01..1 or 1...1 // of the form: 0..01..10..0 or 1..10..01..1 or 1...1
//
// Note: This ignores the upper 32 bits of the input. When a
// zero extended result is desired (e.g a 64 bit result), the
// user must verify the upper 32 bits are 0 and the mask is
// contiguous (that is, non-wrapping).
func isPPC64WordRotateMask(v64 int64) bool { func isPPC64WordRotateMask(v64 int64) bool {
// Isolate rightmost 1 (if none 0) and add. // Isolate rightmost 1 (if none 0) and add.
v := uint32(v64) v := uint32(v64)
@ -1593,6 +1598,16 @@ func isPPC64WordRotateMask(v64 int64) bool {
return (v&vp == 0 || vn&vpn == 0) && v != 0 return (v&vp == 0 || vn&vpn == 0) && v != 0
} }
// Test if this mask is a valid, contiguous bitmask which can be
// represented by a RLWNM mask and also clears the upper 32 bits
// of the register.
func isPPC64WordRotateMaskNonWrapping(v64 int64) bool {
// Isolate rightmost 1 (if none 0) and add.
v := uint32(v64)
vp := (v & -v) + v
return (v&vp == 0) && v != 0 && uint64(uint32(v64)) == uint64(v64)
}
// Compress mask and shift into single value of the form // Compress mask and shift into single value of the form
// me | mb<<8 | rotate<<16 | nbits<<24 where me and mb can // me | mb<<8 | rotate<<16 | nbits<<24 where me and mb can
// be used to regenerate the input mask. // be used to regenerate the input mask.
@ -1702,7 +1717,7 @@ func mergePPC64AndSrdi(m, s int64) int64 {
if rv&uint64(mask) != 0 { if rv&uint64(mask) != 0 {
return 0 return 0
} }
if !isPPC64WordRotateMask(mask) { if !isPPC64WordRotateMaskNonWrapping(mask) {
return 0 return 0
} }
return encodePPC64RotateMask((32-s)&31, mask, 32) return encodePPC64RotateMask((32-s)&31, mask, 32)
@ -1717,7 +1732,7 @@ func mergePPC64AndSldi(m, s int64) int64 {
if rv&uint64(mask) != 0 { if rv&uint64(mask) != 0 {
return 0 return 0
} }
if !isPPC64WordRotateMask(mask) { if !isPPC64WordRotateMaskNonWrapping(mask) {
return 0 return 0
} }
return encodePPC64RotateMask(s&31, mask, 32) return encodePPC64RotateMask(s&31, mask, 32)

10
test/codegen/shift.go
View File

@ -529,6 +529,16 @@ func checkMergedShifts64(a [256]uint32, b [256]uint64, c [256]byte, v uint64) {
b[1] = b[(v>>20)&0xFF] b[1] = b[(v>>20)&0xFF]
// ppc64x: "RLWNM", -"SLD" // ppc64x: "RLWNM", -"SLD"
b[2] = b[((uint64((uint32(v) >> 21)) & 0x3f) << 4)] b[2] = b[((uint64((uint32(v) >> 21)) & 0x3f) << 4)]
// ppc64x: -"RLWNM"
b[3] = (b[3] << 24) & 0xFFFFFF000000
// ppc64x: "RLWNM\t[$]24, R[0-9]+, [$]0, [$]7,"
b[4] = (b[4] << 24) & 0xFF000000
// ppc64x: "RLWNM\t[$]24, R[0-9]+, [$]0, [$]7,"
b[5] = (b[5] << 24) & 0xFF00000F
// ppc64x: -"RLWNM"
b[6] = (b[6] << 0) & 0xFF00000F
// ppc64x: "RLWNM\t[$]4, R[0-9]+, [$]28, [$]31,"
b[7] = (b[7] >> 28) & 0xF
// ppc64x: "RLWNM\t[$]11, R[0-9]+, [$]10, [$]15" // ppc64x: "RLWNM\t[$]11, R[0-9]+, [$]10, [$]15"
c[0] = c[((v>>5)&0x3F)<<16] c[0] = c[((v>>5)&0x3F)<<16]
// ppc64x: "ANDCC\t[$]8064," // ppc64x: "ANDCC\t[$]8064,"