diff options
author | Dale Johannesen <dalej@apple.com> | 2010-03-10 05:45:47 +0000 |
---|---|---|
committer | Dale Johannesen <dalej@apple.com> | 2010-03-10 05:45:47 +0000 |
commit | c5cf227f3dac755508928b9dee8ac6a45dcb4e4f (patch) | |
tree | d81c72600ff18176296fc7decac15c621627c92d /lib/CodeGen | |
parent | fac4f1f1815b54346a805834a8c19d573ce8856c (diff) | |
download | external_llvm-c5cf227f3dac755508928b9dee8ac6a45dcb4e4f.zip external_llvm-c5cf227f3dac755508928b9dee8ac6a45dcb4e4f.tar.gz external_llvm-c5cf227f3dac755508928b9dee8ac6a45dcb4e4f.tar.bz2 |
This survived a bootstrap, so let's try 98104 again.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98137 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r-- | lib/CodeGen/BranchFolding.cpp | 73 |
1 files changed, 69 insertions, 4 deletions
diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp index a937e8f..889763a 100644 --- a/lib/CodeGen/BranchFolding.cpp +++ b/lib/CodeGen/BranchFolding.cpp @@ -347,15 +347,29 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1, --I1; --I2; // Skip debugging pseudos; necessary to avoid changing the code. while (I1->isDebugValue()) { - if (I1==MBB1->begin()) + if (I1==MBB1->begin()) { + while (I2->isDebugValue()) { + if (I2==MBB2->begin()) + // I1==DBG at begin; I2==DBG at begin + return TailLen; + --I2; + } + ++I2; + // I1==DBG at begin; I2==non-DBG, or first of DBGs not at begin return TailLen; + } --I1; } + // I1==first (untested) non-DBG preceding known match while (I2->isDebugValue()) { - if (I2==MBB2->begin()) + if (I2==MBB2->begin()) { + ++I1; + // I1==non-DBG, or first of DBGs not at begin; I2==DBG at begin return TailLen; + } --I2; } + // I1, I2==first (untested) non-DBGs preceding known match if (!I1->isIdenticalTo(I2) || // FIXME: This check is dubious. It's used to get around a problem where // people incorrectly expect inline asm directives to remain in the same @@ -368,6 +382,29 @@ static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1, } ++TailLen; } + // Back past possible debugging pseudos at beginning of block. This matters + // when one block differs from the other only by whether debugging pseudos + // are present at the beginning. (This way, the various checks later for + // I1==MBB1->begin() work as expected.) + if (I1 == MBB1->begin() && I2 != MBB2->begin()) { + --I2; + while (I2->isDebugValue()) { + if (I2 == MBB2->begin()) { + return TailLen; + } + --I2; + } + ++I2; + } + if (I2 == MBB2->begin() && I1 != MBB1->begin()) { + --I1; + while (I1->isDebugValue()) { + if (I1 == MBB1->begin()) + return TailLen; + --I1; + } + ++I1; + } return TailLen; } @@ -934,6 +971,18 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) { return MadeChange; } +// Blocks should be considered empty if they contain only debug info; +// else the debug info would affect codegen. +static bool IsEmptyBlock(MachineBasicBlock *MBB) { + if (MBB->empty()) + return true; + for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end(); + MBBI!=MBBE; ++MBBI) { + if (!MBBI->isDebugValue()) + return false; + } + return true; +} /// IsBetterFallthrough - Return true if it would be clearly better to /// fall-through to MBB1 than to fall through into MBB2. This has to return @@ -971,7 +1020,7 @@ ReoptimizeBlock: // explicitly. Landing pads should not do this since the landing-pad table // points to this block. Blocks with their addresses taken shouldn't be // optimized away. - if (MBB->empty() && !MBB->isLandingPad() && !MBB->hasAddressTaken()) { + if (IsEmptyBlock(MBB) && !MBB->isLandingPad() && !MBB->hasAddressTaken()) { // Dead block? Leave for cleanup later. if (MBB->pred_empty()) return MadeChange; @@ -1163,7 +1212,23 @@ ReoptimizeBlock: // be 'non-branch terminators' in the block, try removing the branch and // then seeing if the block is empty. TII->RemoveBranch(*MBB); - + // If the only things remaining in the block are debug info, remove these + // as well, so this will behave the same as an empty block in non-debug + // mode. + if (!MBB->empty()) { + bool NonDebugInfoFound = false; + for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); + I != E; ++I) { + if (!I->isDebugValue()) { + NonDebugInfoFound = true; + break; + } + } + if (!NonDebugInfoFound) + // Make the block empty, losing the debug info (we could probably + // improve this in some cases.) + MBB->erase(MBB->begin(), MBB->end()); + } // If this block is just an unconditional branch to CurTBB, we can // usually completely eliminate the block. The only case we cannot // completely eliminate the block is when the block before this one |