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cmd/compile: on PPC64, fix sign/zero extension when masking

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(ANDCCconst [y] (MOV.*reg x)) should only be merged when zero
extending. Otherwise, sign bits are lost on negative values.

(ANDCCconst [0xFF] (MOVBreg x)) should be simplified to a zero
extension of x. Likewise for the MOVHreg variant.

Fixes 

Change-Id: I04e4fd7dc6a826e870681f37506620d48393698b
Reviewed-on: https://go-review.googlesource.com/c/go/+/508775
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Paul E. Murphy
2023-07-11 09:07:43 -05:00
committed by Paul Murphy
parent af8f94e3c5
commit 5e4000ad7f
3 changed files with 37 additions and 70 deletions
src/cmd/compile/internal/ssa
_gen
PPC64.rules
rewritePPC64.go
test/codegen
bits.go

20
test/codegen/bits.go

@ -374,3 +374,23 @@ func foldConstOutOfRange(a uint64) uint64 {
// arm64: "MOVD\t[$]19088744",-"ADD\t[$]19088744"
return a + 0x1234568
}
// Verify sign-extended values are not zero-extended under a bit mask (#61297)
func signextendAndMask8to64(a int8) (s, z uint64) {
// ppc64x: "MOVB", "ANDCC\t[$]1015,"
s = uint64(a) & 0x3F7
// ppc64x: -"MOVB", "ANDCC\t[$]247,"
z = uint64(uint8(a)) & 0x3F7
return
}
// Verify zero-extended values are not sign-extended under a bit mask (#61297)
func zeroextendAndMask8to64(a int8, b int16) (x, y uint64) {
// ppc64x: -"MOVB\t", -"ANDCC", "MOVBZ"
x = uint64(a) & 0xFF
// ppc64x: -"MOVH\t", -"ANDCC", "MOVHZ"
y = uint64(b) & 0xFFFF
return
}