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Take advantage of the recent improvements to the liveintervals set (tracking

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instructions which define each value#) to simplify and improve the coallescer.
In particular, this patch:

1. Implements iterative coallescing.
2. Reverts an unsafe hack from handlePhysRegDef, superceeding it with a
   better solution.
3. Implements PR865, "coallescing" away the second copy in code like:

   A = B
   ...
   B = A

This also includes changes to symbolically print registers in intervals
when possible.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29862 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2006-08-24 22:43:55 +00:00
parent 4869d7fa8e
commit f7da2c7b0c
5 changed files with 389 additions and 235 deletions
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lib/CodeGen/VirtRegMap.cpp
+10 -30
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@@ -521,7 +521,6 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// Process all of the spilled uses and all non spilled reg references.
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || MO.getReg() == 0)
continue; // Ignore non-register operands.
@@ -791,37 +790,16 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
}
if (!OpTakenCareOf) {
// 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)) {
if (Src == Dst) {
// Check to see if this is a noop copy. If so, eliminate
// the instruction before considering the dest reg to be
// changed.
++NumDCE;
DEBUG(std::cerr << "Removing now-noop copy: " << MI);
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
} else if (MII != MBB.begin()) {
// Check to see if this is a sequence of the form:
// mov R0, R1
// mov R1, R0
// Eliminate the second move if so.
MachineBasicBlock::iterator PrevMII = MII; --PrevMII;
MachineInstr& PrevMI = *PrevMII;
unsigned PrevSrc, PrevDst;
if (TII->isMoveInstr(PrevMI, PrevSrc, PrevDst))
if (PrevSrc == Dst && PrevDst == Src) {
++NumDCE;
DEBUG(std::cerr << "Removing now-noop copy: " << MI);
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
}
}
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DEBUG(std::cerr << "Removing now-noop copy: " << MI);
MBB.erase(&MI);
VRM.RemoveFromFoldedVirtMap(&MI);
goto ProcessNextInst;
}
Spills.ClobberPhysReg(VirtReg);
continue;
}
@@ -883,6 +861,8 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
}
}
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");