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Ever more complicated DEBUG_VALUE fixes for branch folding.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98104 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -347,15 +347,29 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
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--I1; --I2;
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// Skip debugging pseudos; necessary to avoid changing the code.
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while (I1->isDebugValue()) {
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if (I1==MBB1->begin())
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if (I1==MBB1->begin()) {
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while (I2->isDebugValue()) {
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if (I2==MBB2->begin())
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// I1==DBG at begin; I2==DBG at begin
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return TailLen;
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--I2;
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}
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++I2;
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// I1==DBG at begin; I2==non-DBG, or first of DBGs not at begin
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return TailLen;
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}
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--I1;
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}
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// I1==first (untested) non-DBG preceding known match
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while (I2->isDebugValue()) {
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if (I2==MBB2->begin())
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if (I2==MBB2->begin()) {
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++I1;
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// I1==non-DBG, or first of DBGs not at begin; I2==DBG at begin
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return TailLen;
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}
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--I2;
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}
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// I1, I2==first (untested) non-DBGs preceding known match
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if (!I1->isIdenticalTo(I2) ||
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// FIXME: This check is dubious. It's used to get around a problem where
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// people incorrectly expect inline asm directives to remain in the same
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@ -368,6 +382,29 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
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}
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++TailLen;
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}
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// Back past possible debugging pseudos at beginning of block. This matters
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// when one block differs from the other only by whether debugging pseudos
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// are present at the beginning. (This way, the various checks later for
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// I1==MBB1->begin() work as expected.)
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if (I1 == MBB1->begin() && I2 != MBB2->begin()) {
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--I2;
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while (I2->isDebugValue()) {
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if (I2 == MBB2->begin()) {
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return TailLen;
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}
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--I2;
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}
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++I2;
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}
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if (I2 == MBB2->begin() && I1 != MBB1->begin()) {
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--I1;
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while (I1->isDebugValue()) {
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if (I1 == MBB1->begin())
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return TailLen;
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--I1;
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}
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++I1;
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}
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return TailLen;
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}
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@ -1163,7 +1200,23 @@ ReoptimizeBlock:
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// be 'non-branch terminators' in the block, try removing the branch and
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// then seeing if the block is empty.
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TII->RemoveBranch(*MBB);
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// If the only things remaining in the block are debug info, remove these
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// as well, so this will behave the same as an empty block in non-debug
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// mode.
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if (!MBB->empty()) {
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bool NonDebugInfoFound = false;
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for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
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I != E; ++I) {
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if (!I->isDebugValue()) {
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NonDebugInfoFound = true;
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break;
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}
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}
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if (!NonDebugInfoFound)
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// Make the block empty, losing the debug info (we could probably
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// improve this in some cases.)
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MBB->erase(MBB->begin(), MBB->end());
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}
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// If this block is just an unconditional branch to CurTBB, we can
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// usually completely eliminate the block. The only case we cannot
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// completely eliminate the block is when the block before this one
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