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Simplify this code: don't call AnalyzeBranch before doing simpler checks.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90633 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-12-05 00:32:59 +00:00
parent 07f111e7b7
commit 735985fbbe
1 changed files with 13 additions and 13 deletions
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26
lib/CodeGen/MachineBasicBlock.cpp
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@@ -363,11 +363,6 @@ bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
} }
bool MachineBasicBlock::canFallThrough() { bool MachineBasicBlock::canFallThrough() {
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
bool BranchUnAnalyzable = TII->AnalyzeBranch(*this, TBB, FBB, Cond, true);
MachineFunction::iterator Fallthrough = this; MachineFunction::iterator Fallthrough = this;
++Fallthrough; ++Fallthrough;
// If FallthroughBlock is off the end of the function, it can't fall through. // If FallthroughBlock is off the end of the function, it can't fall through.
@@ -378,16 +373,21 @@ bool MachineBasicBlock::canFallThrough() {
if (!isSuccessor(Fallthrough)) if (!isSuccessor(Fallthrough))
return false; return false;
// If we couldn't analyze the branch, examine the last instruction. // Analyze the branches, if any, at the end of the block.
// If the block doesn't end in a known control barrier, assume fallthrough MachineBasicBlock *TBB = 0, *FBB = 0;
// is possible. The isPredicable check is needed because this code can be SmallVector<MachineOperand, 4> Cond;
// called during IfConversion, where an instruction which is normally a const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
// Barrier is predicated and thus no longer an actual control barrier. This if (TII->AnalyzeBranch(*this, TBB, FBB, Cond, true)) {
// is over-conservative though, because if an instruction isn't actually // If we couldn't analyze the branch, examine the last instruction.
// predicated we could still treat it like a barrier. // If the block doesn't end in a known control barrier, assume fallthrough
if (BranchUnAnalyzable) // is possible. The isPredicable check is needed because this code can be
// called during IfConversion, where an instruction which is normally a
// Barrier is predicated and thus no longer an actual control barrier. This
// is over-conservative though, because if an instruction isn't actually
// predicated we could still treat it like a barrier.
return empty() || !back().getDesc().isBarrier() || return empty() || !back().getDesc().isBarrier() ||
back().getDesc().isPredicable(); back().getDesc().isPredicable();
}
// If there is no branch, control always falls through. // If there is no branch, control always falls through.
if (TBB == 0) return true; if (TBB == 0) return true;