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| author | Cherry Zhang <cherryyz@google.com> | 2021-04-28 11:00:15 -0400 |
|---|---|---|
| committer | Cherry Zhang <cherryyz@google.com> | 2021-04-28 16:13:40 +0000 |
| commit | 5b328c4a2fbae10ec10d233d691435fe0295fc39 (patch) | |
| tree | d51e0e4a88299a65dbd9087ccc5c09f0a9db709e /src/cmd/compile/internal/ssa/regalloc.go | |
| parent | cbb3f090477de92a7e158050803ef71a5ea825ee (diff) | |
| download | go-5b328c4a2fbae10ec10d233d691435fe0295fc39.tar.gz go-5b328c4a2fbae10ec10d233d691435fe0295fc39.zip | |
cmd/compile: use desired register only if it satisfies register mask
In the register allocator, if possible, we allocate a value to its
desired register (the ideal register for its next use). In some
cases the desired register does not satisfies the value's output
register mask. We should not use the register in this case.
In the following example, v33 is going to be returned as a
function result, so it is allocated to its desired register AX.
However, its Op cannot use AX as output, causing miscompilation.
v33 = CMOVQEQF <int> v24 v28 v29 : AX (~R0[int])
v35 = MakeResult <int,int,mem> v33 v26 v18
Ret v35
Change-Id: Id0f4f27c4b233ee297e83077e3c8494fe193e664
Reviewed-on: https://go-review.googlesource.com/c/go/+/314630
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Diffstat (limited to 'src/cmd/compile/internal/ssa/regalloc.go')
| -rw-r--r-- | src/cmd/compile/internal/ssa/regalloc.go | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go index 8ddb3d045b..c81d5574fe 100644 --- a/src/cmd/compile/internal/ssa/regalloc.go +++ b/src/cmd/compile/internal/ssa/regalloc.go @@ -1493,9 +1493,9 @@ func (s *regAllocState) regalloc(f *Func) { goto ok } - // Try to move an input to the desired output. + // Try to move an input to the desired output, if allowed. for _, r := range dinfo[idx].out { - if r != noRegister && m>>r&1 != 0 { + if r != noRegister && (m®spec.outputs[0].regs)>>r&1 != 0 { m = regMask(1) << r args[0] = s.allocValToReg(v.Args[0], m, true, v.Pos) // Note: we update args[0] so the instruction will @@ -1569,6 +1569,9 @@ func (s *regAllocState) regalloc(f *Func) { if !opcodeTable[v.Op].commutative { // Output must use the same register as input 0. r := register(s.f.getHome(args[0].ID).(*Register).num) + if mask>>r&1 == 0 { + s.f.Fatalf("resultInArg0 value's input %v cannot be an output of %s", s.f.getHome(args[0].ID).(*Register), v.LongString()) + } mask = regMask(1) << r } else { // Output must use the same register as input 0 or 1. |