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Avoid sinking machine instructions into a loop.

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MachineLoopInfo is already available when MachineSinking runs, so the check is
free.

There is no test case because it would require a critical edge into a loop, and
CodeGenPrepare splits those. This check is just to be extra careful.

llvm-svn: 101420
This commit is contained in:
Jakob Stoklund Olesen 2010-04-15 23:41:02 +00:00
parent 0017916a36
commit 00bd3bcbe4
1 changed files with 11 additions and 0 deletions
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11
lib/CodeGen/MachineSink.cpp
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@ -20,6 +20,7 @@
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
@ -37,6 +38,7 @@ namespace {
const TargetRegisterInfo *TRI;
MachineRegisterInfo *RegInfo; // Machine register information
MachineDominatorTree *DT; // Machine dominator tree
MachineLoopInfo *LI;
AliasAnalysis *AA;
BitVector AllocatableSet; // Which physregs are allocatable?
@ -51,7 +53,9 @@ namespace {
MachineFunctionPass::getAnalysisUsage(AU);
AU.addRequired<AliasAnalysis>();
AU.addRequired<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
}
private:
bool ProcessBlock(MachineBasicBlock &MBB);
@ -102,6 +106,7 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
TRI = TM.getRegisterInfo();
RegInfo = &MF.getRegInfo();
DT = &getAnalysis<MachineDominatorTree>();
LI = &getAnalysis<MachineLoopInfo>();
AA = &getAnalysis<AliasAnalysis>();
AllocatableSet = TRI->getAllocatableSet(MF);
@ -291,6 +296,12 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
return false;
}
// Don't sink instructions into a loop.
if (LI->isLoopHeader(SuccToSinkTo)) {
DEBUG(dbgs() << " *** PUNTING: Loop header found\n");
return false;
}
// Otherwise we are OK with sinking along a critical edge.
DEBUG(dbgs() << "Sinking along critical edge.\n");
}