- Revert some changes from 85044, 85045, and 85047 that broke x86_64 tests and
bootstrapping. It's not safe to leave identity subreg_to_reg and insert_subreg
around.
- Relax register scavenging to allow use of partially "not-live" registers. It's
common for targets to operate on registers where the top bits are undef. e.g.
s0 =
d0 = insert_subreg d0<undef>, s0, 1
...
= d0
When the insert_subreg is eliminated by the coalescer, the scavenger used to
complain. The previous fix was to keep to insert_subreg around. But that's
brittle and it's overly conservative when we want to use the scavenger to
allocate registers. It's actually legal and desirable for other instructions
to use the "undef" part of d0. e.g.
s0 =
d0 = insert_subreg d0<undef>, s0, 1
...
s1 =
= s1
= d0
We probably need add a "partial-undef" marker on machine operand so the
machine verifier would not complain.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85091 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index 7e060c0..107c19a 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -495,7 +495,7 @@
MachineOperand *DefOp = NULL;
for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = DefMI->getOperand(i);
- if (!MO.isReg() || MO.isUse() || !MO.isKill() || MO.isUndef())
+ if (!MO.isReg() || !MO.isUse() || !MO.isKill() || MO.isUndef())
continue;
if (MO.getReg() == Reg)
DefOp = &MO;
@@ -2258,7 +2258,7 @@
// eliminate this or else the undef marker is lost and it will
// confuses the scavenger. This is extremely rare.
unsigned Src, Dst, SrcSR, DstSR;
- if (TII->isIdentityCopy(MI, Src, Dst, SrcSR, DstSR) &&
+ if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst &&
!MI.findRegisterUseOperand(Src)->isUndef()) {
++NumDCE;
DEBUG(errs() << "Removing now-noop copy: " << MI);
@@ -2347,7 +2347,7 @@
// instruction before considering the dest reg to be changed.
{
unsigned Src, Dst, SrcSR, DstSR;
- if (TII->isIdentityCopy(MI, Src, Dst, SrcSR, DstSR)) {
+ if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst) {
++NumDCE;
DEBUG(errs() << "Removing now-noop copy: " << MI);
InvalidateKills(MI, TRI, RegKills, KillOps);