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Add a hidden option to PHIElimination to split all critical edges. This is 

particularly useful for catching issues with architectures that have exotic
terminators like MIPS.

llvm-svn: 174938
This commit is contained in:
Cameron Zwarich 2013-02-12 03:49:25 +00:00
parent 6d7a4e0c9c
commit 15eb925ed4
1 changed files with 9 additions and 4 deletions
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13
llvm/lib/CodeGen/PHIElimination.cpp
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@ -40,6 +40,11 @@ DisableEdgeSplitting("disable-phi-elim-edge-splitting", cl::init(false),
cl::Hidden, cl::desc("Disable critical edge splitting "
"during PHI elimination"));
static cl::opt<bool>
SplitAllCriticalEdges("phi-elim-split-all-critical-edges", cl::init(false),
cl::Hidden, cl::desc("Split all critical edges during "
"PHI elimination"));
namespace {
class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information
@ -550,10 +555,10 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// Avoid splitting backedges of loops. It would introduce small
// out-of-line blocks into the loop which is very bad for code placement.
if (PreMBB == &MBB)
if (PreMBB == &MBB && !SplitAllCriticalEdges)
continue;
const MachineLoop *PreLoop = MLI ? MLI->getLoopFor(PreMBB) : 0;
if (IsLoopHeader && PreLoop == CurLoop)
if (IsLoopHeader && PreLoop == CurLoop && !SplitAllCriticalEdges)
continue;
// LV doesn't consider a phi use live-out, so isLiveOut only returns true
@ -562,7 +567,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// there is a risk it may not be coalesced away.
//
// If the copy would be a kill, there is no need to split the edge.
if (!isLiveOutPastPHIs(Reg, PreMBB))
if (!isLiveOutPastPHIs(Reg, PreMBB) && !SplitAllCriticalEdges)
continue;
DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#"
@ -577,7 +582,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// is likely to be left after coalescing. If we are looking at a loop
// exiting edge, split it so we won't insert code in the loop, otherwise
// don't bother.
bool ShouldSplit = !isLiveIn(Reg, &MBB);
bool ShouldSplit = !isLiveIn(Reg, &MBB) || SplitAllCriticalEdges;
// Check for a loop exiting edge.
if (!ShouldSplit && CurLoop != PreLoop) {