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Fixed a long standing spiller bug that's exposed by Thumb: 

The code sequence before the spiller is something like:
                 = tMOVrr
        %reg1117 = tMOVrr
        %reg1078 = tLSLri %reg1117, 2

The it starts spilling:
        %r0 = tRestore <fi#5>, 0
        %r1 = tRestore <fi#7>, 0
        %r1 = tMOVrr %r1<kill>
        tSpill %r1, <fi#5>, 0
        %reg1078 = tLSLri %reg1117, 2

It restores the value while processing the first tMOVrr. At this point, the
spiller remembers fi#5 is available in %r0. Next it processes the second move.
It restores the source before the move and spills the result afterwards. The
move becomes a noop and is deleted. However, a spill has been inserted and that
should invalidate reuse of %r0 for fi#5 and add reuse of %r1 for fi#5.
Therefore, %reg1117 (which is also assigned fi#5) should get %r1, not %r0.

llvm-svn: 34039
This commit is contained in:
Evan Cheng 2007-02-08 06:04:54 +00:00
parent 0591d43ea1
commit 6ad6fdb70b
1 changed files with 13 additions and 13 deletions
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26
llvm/lib/CodeGen/VirtRegMap.cpp
View File

@ -923,19 +923,6 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
DOUT << "Store:\t" << *next(MII);
MI.getOperand(i).setReg(PhysReg);
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
{
unsigned Src, Dst;
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
}
}
// If there is a dead store to this stack slot, nuke it now.
MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
if (LastStore) {
@ -953,6 +940,19 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
Spills.ClobberPhysReg(PhysReg);
Spills.addAvailable(StackSlot, PhysReg);
++NumStores;
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
{
unsigned Src, Dst;
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
}
}
}
}
ProcessNextInst: