[llvm-commits] [llvm] r159722 - /llvm/trunk/lib/CodeGen/PHIElimination.cpp
Jakob Stoklund Olesen
stoklund at 2pi.dk
Wed Jul 4 12:52:06 PDT 2012
Author: stoklund
Date: Wed Jul 4 14:52:05 2012
New Revision: 159722
URL: http://llvm.org/viewvc/llvm-project?rev=159722&view=rev
Log:
Allow multiple terminators to read virtual registers.
Find the kill as the last terminator to read SrcReg.
Patch by Philipp Brüschweiler!
Modified:
llvm/trunk/lib/CodeGen/PHIElimination.cpp
Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=159722&r1=159721&r2=159722&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Wed Jul 4 14:52:05 2012
@@ -194,7 +194,7 @@
/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
-/// under the assuption that it needs to be lowered in a way that supports
+/// under the assumption that it needs to be lowered in a way that supports
/// atomic execution of PHIs. This lowering method is always correct all of the
/// time.
///
@@ -355,39 +355,35 @@
// add a kill marker in this block saying that it kills the incoming value!
if (!ValueIsUsed && !LV->isLiveOut(SrcReg, opBlock)) {
// In our final twist, we have to decide which instruction kills the
- // register. In most cases this is the copy, however, the first
- // terminator instruction at the end of the block may also use the value.
- // In this case, we should mark *it* as being the killing block, not the
- // copy.
- MachineBasicBlock::iterator KillInst;
- MachineBasicBlock::iterator Term = opBlock.getFirstTerminator();
- if (Term != opBlock.end() && Term->readsRegister(SrcReg)) {
- KillInst = Term;
-
- // Check that no other terminators use values.
-#ifndef NDEBUG
- for (MachineBasicBlock::iterator TI = llvm::next(Term);
- TI != opBlock.end(); ++TI) {
- if (TI->isDebugValue())
- continue;
- assert(!TI->readsRegister(SrcReg) &&
- "Terminator instructions cannot use virtual registers unless"
- "they are the first terminator in a block!");
- }
-#endif
- } else if (reusedIncoming || !IncomingReg) {
- // We may have to rewind a bit if we didn't insert a copy this time.
- KillInst = Term;
- while (KillInst != opBlock.begin()) {
- --KillInst;
- if (KillInst->isDebugValue())
- continue;
- if (KillInst->readsRegister(SrcReg))
- break;
+ // register. In most cases this is the copy, however, terminator
+ // instructions at the end of the block may also use the value. In this
+ // case, we should mark the last such terminator as being the killing
+ // block, not the copy.
+ MachineBasicBlock::iterator KillInst = opBlock.end();
+ MachineBasicBlock::iterator FirstTerm = opBlock.getFirstTerminator();
+ for (MachineBasicBlock::iterator Term = FirstTerm;
+ Term != opBlock.end(); ++Term) {
+ if (Term->readsRegister(SrcReg))
+ KillInst = Term;
+ }
+
+ if (KillInst == opBlock.end()) {
+ // No terminator uses the register.
+
+ if (reusedIncoming || !IncomingReg) {
+ // We may have to rewind a bit if we didn't insert a copy this time.
+ KillInst = FirstTerm;
+ while (KillInst != opBlock.begin()) {
+ --KillInst;
+ if (KillInst->isDebugValue())
+ continue;
+ if (KillInst->readsRegister(SrcReg))
+ break;
+ }
+ } else {
+ // We just inserted this copy.
+ KillInst = prior(InsertPos);
}
- } else {
- // We just inserted this copy.
- KillInst = prior(InsertPos);
}
assert(KillInst->readsRegister(SrcReg) && "Cannot find kill instruction");
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