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

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174938 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Cameron Zwarich
2013-02-12 03:49:25 +00:00
parent 1fc88933e6
commit 5758a711f4
1 changed files with 9 additions and 4 deletions
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13
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 " cl::Hidden, cl::desc("Disable critical edge splitting "
"during PHI elimination")); "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 { namespace {
class PHIElimination : public MachineFunctionPass { class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information MachineRegisterInfo *MRI; // Machine register information
@@ -550,10 +555,10 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
// Avoid splitting backedges of loops. It would introduce small // Avoid splitting backedges of loops. It would introduce small
// out-of-line blocks into the loop which is very bad for code placement. // out-of-line blocks into the loop which is very bad for code placement.
if (PreMBB == &MBB) if (PreMBB == &MBB && !SplitAllCriticalEdges)
continue; continue;
const MachineLoop *PreLoop = MLI ? MLI->getLoopFor(PreMBB) : 0; const MachineLoop *PreLoop = MLI ? MLI->getLoopFor(PreMBB) : 0;
if (IsLoopHeader && PreLoop == CurLoop) if (IsLoopHeader && PreLoop == CurLoop && !SplitAllCriticalEdges)
continue; continue;
// LV doesn't consider a phi use live-out, so isLiveOut only returns true // 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. // 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 the copy would be a kill, there is no need to split the edge.
if (!isLiveOutPastPHIs(Reg, PreMBB)) if (!isLiveOutPastPHIs(Reg, PreMBB) && !SplitAllCriticalEdges)
continue; continue;
DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#" 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 // 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 // exiting edge, split it so we won't insert code in the loop, otherwise
// don't bother. // don't bother.
bool ShouldSplit = !isLiveIn(Reg, &MBB); bool ShouldSplit = !isLiveIn(Reg, &MBB) || SplitAllCriticalEdges;
// Check for a loop exiting edge. // Check for a loop exiting edge.
if (!ShouldSplit && CurLoop != PreLoop) { if (!ShouldSplit && CurLoop != PreLoop) {