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cmd/compile: fix ANDI/SRWI merge on ppc64

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The shift amount should be masked to avoid rotation values
beyond the numer of bits. In this case, if the shift amount
is 0, it should rotate 0, not 32.

Fixes #45589

Change-Id: I1e764497a39d0ec128e29af42352b70c70b2ecc5
Reviewed-on: https://go-review.googlesource.com/c/go/+/310569
Run-TryBot: Paul Murphy <murp@ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Carlos Eduardo Seo <carlos.seo@linaro.org>
Trust: Carlos Eduardo Seo <carlos.seo@linaro.org>
This commit is contained in:
Paul E. Murphy 2021-04-15 13:41:01 -05:00 • committed by Carlos Eduardo Seo
parent 699a7c0fe9
commit c8fb0ec5a0
2 changed files with 2 additions and 1 deletions
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2
src/cmd/compile/internal/ssa/rewrite.go
View file

@ -1492,7 +1492,7 @@ func mergePPC64AndSrwi(m, s int64) int64 {
if !isPPC64WordRotateMask(mask) {
return 0
}
return encodePPC64RotateMask(32-s, mask, 32)
return encodePPC64RotateMask((32-s)&31, mask, 32)
}
// Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.

1
src/cmd/compile/internal/ssa/rewrite_test.go
View file

@ -205,6 +205,7 @@ func TestMergePPC64AndSrwi(t *testing.T) {
{0x00000000, 4, false, 0, 0},
{0xF0000000, 4, false, 0, 0},
{0xF0000000, 32, false, 0, 0},
{0xFFFFFFFF, 0, true, 0, 0xFFFFFFFF},
}
for i, v := range tests {
result := mergePPC64AndSrwi(v.and, v.srw)