Added a check so that if we have two machine instructions in this form
MOV R0, R1
MOV R1, R0
the second machine instruction is removed. Added a regression test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29792 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp
index bc56945..7e6d09b 100644
--- a/lib/CodeGen/VirtRegMap.cpp
+++ b/lib/CodeGen/VirtRegMap.cpp
@@ -521,6 +521,7 @@
// 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.
@@ -790,16 +791,37 @@
}
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) && Src == Dst) {
- ++NumDCE;
- DEBUG(std::cerr << "Removing now-noop copy: " << MI);
- MBB.erase(&MI);
- VRM.RemoveFromFoldedVirtMap(&MI);
- goto ProcessNextInst;
+ 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;
+ }
+ }
}
+
Spills.ClobberPhysReg(VirtReg);
continue;
}
@@ -861,8 +883,6 @@
}
}
-
-
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");