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[release-branch.go1.16] cmd/compile: fix ANDI/SRWI merge on ppc64 

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 #45636

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>
(cherry picked from commit c8fb0ec5a0)
Reviewed-on: https://go-review.googlesource.com/c/go/+/311378
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>
This commit is contained in:
Paul E. Murphy 2021-04-15 13:41:01 -05:00 committed by Carlos Amedee
parent ea0537f2fc
commit 7e709791c2
2 changed files with 2 additions and 1 deletions
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2
src/cmd/compile/internal/ssa/rewrite.go
View File

@ -1469,7 +1469,7 @@ 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)