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don't break infinite loops

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llvm-svn: 31102
This commit is contained in:
Chris Lattner 2006-10-21 06:11:43 +00:00
parent a9adb1e558
commit 9e7d74961b
1 changed files with 19 additions and 6 deletions
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25
lib/CodeGen/BranchFolding.cpp
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@ -499,7 +499,7 @@ void BranchFolder::OptimizeBlock(MachineFunction::iterator MBB) {
// If this branch is the only thing in its block, see if we can forward // If this branch is the only thing in its block, see if we can forward
// other blocks across it. // other blocks across it.
if (CurTBB && CurCond.empty() && CurFBB == 0 && if (CurTBB && CurCond.empty() && CurFBB == 0 &&
TII->isBranch(MBB->begin()->getOpcode())) { TII->isBranch(MBB->begin()->getOpcode()) && CurTBB != &*MBB) {
// This block may contain just an unconditional branch. Because there can // This block may contain just an unconditional branch. Because there can
// be 'non-branch terminators' in the block, try removing the branch and // be 'non-branch terminators' in the block, try removing the branch and
// then seeing if the block is empty. // then seeing if the block is empty.
@ -526,15 +526,28 @@ void BranchFolder::OptimizeBlock(MachineFunction::iterator MBB) {
} }
// Iterate through all the predecessors, revectoring each in-turn. // Iterate through all the predecessors, revectoring each in-turn.
while (!MBB->pred_empty()) MachineBasicBlock::pred_iterator PI = MBB->pred_begin();
ReplaceUsesOfBlockWith(*(MBB->pred_end()-1), MBB, CurTBB, TII); bool DidChange = false;
bool HasBranchToSelf = false;
while (PI != MBB->pred_end()) {
if (*PI == &*MBB) {
// If this block has an uncond branch to itself, leave it.
++PI;
HasBranchToSelf = true;
} else {
DidChange = true;
ReplaceUsesOfBlockWith(*PI, MBB, CurTBB, TII);
}
}
// Change any jumptables to go to the new MBB. // Change any jumptables to go to the new MBB.
MBB->getParent()->getJumpTableInfo()->ReplaceMBBInJumpTables(MBB, MBB->getParent()->getJumpTableInfo()->ReplaceMBBInJumpTables(MBB,
CurTBB); CurTBB);
++NumBranchOpts; if (DidChange) {
MadeChange = true; ++NumBranchOpts;
return; MadeChange = true;
if (!HasBranchToSelf) return;
}
} }
// Add the branch back if the block is more than just an uncond branch. // Add the branch back if the block is more than just an uncond branch.