diff options
| author | Keith Randall <khr@golang.org> | 2023-12-14 13:07:50 -0800 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2023-12-15 19:35:21 +0000 |
| commit | b60bf8f8e131b026eb2691e736d3df9dce852297 (patch) | |
| tree | 4ddaf9a9843712e08e4aa78fee48bf72c957552b /src/cmd/internal/obj/arm | |
| parent | 5e939b3a9ce7864551e86c04a05db887c25e2759 (diff) | |
| download | go-b60bf8f8e131b026eb2691e736d3df9dce852297.tar.xz | |
cmd/asm: fix encoding for arm right shift by constant 0
Right shifts, for some odd reasons, can encode shifts of constant
1-32 instead of 0-31. Left shifts, however, can encode shifts 0-31.
When the shift amount is 0, arm recommends encoding right shifts
using left shifts.
Fixes #64715
Change-Id: Id3825349aa7195028037893dfe01fa0e405eaa51
Reviewed-on: https://go-review.googlesource.com/c/go/+/549955
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Diffstat (limited to 'src/cmd/internal/obj/arm')
| -rw-r--r-- | src/cmd/internal/obj/arm/asm5.go | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go index 24b9bdd980..9731bd4151 100644 --- a/src/cmd/internal/obj/arm/asm5.go +++ b/src/cmd/internal/obj/arm/asm5.go @@ -1099,6 +1099,14 @@ func (c *ctxt5) oplook(p *obj.Prog) *Optab { fmt.Printf("\t\t%d %d\n", p.From.Type, p.To.Type) } + if (p.As == ASRL || p.As == ASRA) && p.From.Type == obj.TYPE_CONST && p.From.Offset == 0 { + // Right shifts are weird - a shift that looks like "shift by constant 0" actually + // means "shift by constant 32". Use left shift in this situation instead. + // See issue 64715. + // TODO: rotate by 0? Not currently supported, but if we ever do then include it here. + p.As = ASLL + } + ops := oprange[p.As&obj.AMask] c1 := &xcmp[a1] c3 := &xcmp[a3] |