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Teach isSafeToClobberEFLAGS to ignore dbg_value's. We need a MachineBasicBlock::iterator that does this automatically?

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99320 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2010-03-23 20:35:45 +00:00
parent 112e5e7eff
commit 8d1f0dd983
1 changed files with 13 additions and 3 deletions
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16
lib/Target/X86/X86InstrInfo.cpp
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@ -992,8 +992,10 @@ X86InstrInfo::isReallyTriviallyReMaterializable(const MachineInstr *MI,
/// a few instructions in each direction it assumes it's not safe.
static bool isSafeToClobberEFLAGS(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
MachineBasicBlock::iterator E = MBB.end();
// It's always safe to clobber EFLAGS at the end of a block.
if (I == MBB.end())
if (I == E)
return true;
// For compile time consideration, if we are not able to determine the
@ -1017,20 +1019,28 @@ static bool isSafeToClobberEFLAGS(MachineBasicBlock &MBB,
// This instruction defines EFLAGS, no need to look any further.
return true;
++Iter;
// Skip over DBG_VALUE.
while (Iter != E && Iter->isDebugValue())
++Iter;
// If we make it to the end of the block, it's safe to clobber EFLAGS.
if (Iter == MBB.end())
if (Iter == E)
return true;
}
MachineBasicBlock::iterator B = MBB.begin();
Iter = I;
for (unsigned i = 0; i < 4; ++i) {
// If we make it to the beginning of the block, it's safe to clobber
// EFLAGS iff EFLAGS is not live-in.
if (Iter == MBB.begin())
if (Iter == B)
return !MBB.isLiveIn(X86::EFLAGS);
--Iter;
// Skip over DBG_VALUE.
while (Iter != B && Iter->isDebugValue())
--Iter;
bool SawKill = false;
for (unsigned j = 0, e = Iter->getNumOperands(); j != e; ++j) {
MachineOperand &MO = Iter->getOperand(j);