Take advantage of the recent improvements to the liveintervals set (tracking
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
diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp
index 7e6d09b..bc56945 100644
--- a/lib/CodeGen/VirtRegMap.cpp
+++ b/lib/CodeGen/VirtRegMap.cpp
@@ -521,7 +521,6 @@
// 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 @@
}
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 @@
}
}
+
+
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");