[llvm-commits] CVS: llvm/lib/CodeGen/IfConversion.cpp
Evan Cheng
evan.cheng at apple.com
Tue Jun 5 16:46:41 PDT 2007
Changes in directory llvm/lib/CodeGen:
IfConversion.cpp updated: 1.28 -> 1.29
---
Log message:
Fix diamond shape ifcvt bugs.
---
Diffs of the changes: (+41 -61)
IfConversion.cpp | 102 ++++++++++++++++++++++---------------------------------
1 files changed, 41 insertions(+), 61 deletions(-)
Index: llvm/lib/CodeGen/IfConversion.cpp
diff -u llvm/lib/CodeGen/IfConversion.cpp:1.28 llvm/lib/CodeGen/IfConversion.cpp:1.29
--- llvm/lib/CodeGen/IfConversion.cpp:1.28 Tue Jun 5 17:03:53 2007
+++ llvm/lib/CodeGen/IfConversion.cpp Tue Jun 5 18:46:14 2007
@@ -284,7 +284,7 @@
}
} else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond &&
TrueBBI.BB->pred_size() == 1 &&
- TrueBBI.BB->pred_size() == 1 &&
+ FalseBBI.BB->pred_size() == 1 &&
// Check the 'true' and 'false' blocks if either isn't ended with
// a branch. If the block does not fallthrough to another block
// then we need to add a branch to its successor.
@@ -301,7 +301,7 @@
// TBB FBB
// \ /
// TailBB
- // Note MBB can be empty in case both TBB and FBB are return blocks.
+ // Note TailBB can be empty.
BBI.Kind = ICDiamond;
TrueBBI.Kind = FalseBBI.Kind = ICChild;
BBI.TailBB = TrueBBI.TrueBB;
@@ -611,74 +611,58 @@
--TrueBBI.NonPredSize;
}
- // Check the 'true' and 'false' blocks if either isn't ended with a branch.
- // Either the block fallthrough to another block or it ends with a
- // return. If it's the former, add a branch to its successor.
- bool TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
- bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
-
// Merge the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block. That is, unless the true
// block would clobber the predicate, in that case, do the opposite.
+ BBInfo *BBI1 = &TrueBBI;
+ BBInfo *BBI2 = &FalseBBI;
std::vector<MachineOperand> RevCond(BBI.BrCond);
TII->ReverseBranchCondition(RevCond);
- BBInfo *CvtBBI;
- if (!TrueBBI.ModifyPredicate) {
- // Predicate the 'true' block after removing its branch.
- TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
- PredicateBlock(TrueBBI, BBI.BrCond);
-
- // Predicate the 'false' block.
- PredicateBlock(FalseBBI, RevCond, true);
-
- if (TrueNeedBr)
- TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL,
- BBI.BrCond);
- // Add an unconditional branch from 'false' to to 'false' successor if it
- // will not be the fallthrough block.
- if (FalseNeedBr &&
- !isNextBlock(BBI.BB, *BBI.FalseBB->succ_begin()))
- InsertUncondBranch(BBI.FalseBB, *BBI.FalseBB->succ_begin(), TII);
- MergeBlocks(TrueBBI, FalseBBI);
- CvtBBI = &TrueBBI;
- } else {
- // Predicate the 'false' block after removing its branch.
- FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB);
- PredicateBlock(FalseBBI, RevCond);
-
- // Predicate the 'false' block.
- PredicateBlock(TrueBBI, BBI.BrCond, true);
-
- // Add a conditional branch from 'false' to 'false' successor if needed.
- if (FalseNeedBr)
- TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
- RevCond);
- // Add an unconditional branch from 'true' to to 'true' successor if it
- // will not be the fallthrough block.
- if (TrueNeedBr &&
- !isNextBlock(BBI.BB, *BBI.TrueBB->succ_begin()))
- InsertUncondBranch(BBI.TrueBB, *BBI.TrueBB->succ_begin(), TII);
- MergeBlocks(FalseBBI, TrueBBI);
- CvtBBI = &FalseBBI;
+ std::vector<MachineOperand> *Cond1 = &BBI.BrCond;
+ std::vector<MachineOperand> *Cond2 = &RevCond;
+ if (TrueBBI.ModifyPredicate) {
+ std::swap(BBI1, BBI2);
+ std::swap(Cond1, Cond2);
}
+ // Check the 'true' and 'false' blocks if either isn't ended with a branch.
+ // Either the block fallthrough to another block or it ends with a
+ // return. If it's the former, add a branch to its successor.
+ bool NeedBr1 = !BBI1->TrueBB && BBI1->BB->succ_size();
+ bool NeedBr2 = !BBI2->TrueBB && BBI1->BB->succ_size();
+
+ // Predicate the 'true' block after removing its branch.
+ BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
+ PredicateBlock(*BBI1, *Cond1);
+
+ // Add an early exit branch if needed.
+ if (NeedBr1)
+ TII->InsertBranch(*BBI1->BB, *BBI1->BB->succ_begin(), NULL, *Cond1);
+
+ // Predicate the 'false' block.
+ PredicateBlock(*BBI2, *Cond2, true);
+
+ // Add an unconditional branch from 'false' to to 'false' successor if it
+ // will not be the fallthrough block.
+ if (NeedBr2 && !isNextBlock(BBI2->BB, *BBI2->BB->succ_begin()))
+ InsertUncondBranch(BBI2->BB, *BBI2->BB->succ_begin(), TII);
+
+ // Keep them as two separate blocks if there is an early exit.
+ if (!NeedBr1)
+ MergeBlocks(*BBI1, *BBI2);
+ else if (!isNextBlock(BBI1->BB, BBI2->BB))
+ InsertUncondBranch(BBI1->BB, BBI2->BB, TII);
+
// Remove the conditional branch from entry to the blocks.
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
- bool OkToIfcvt = true;
- // Merge the combined block into the entry of the diamond if the entry
- // block is its only predecessor. Otherwise, insert an unconditional
- // branch from entry to the if-converted block.
- if (CvtBBI->BB->pred_size() == 1) {
- MergeBlocks(BBI, *CvtBBI);
- CvtBBI = &BBI;
- OkToIfcvt = false;
- } else if (!isNextBlock(BBI.BB, CvtBBI->BB))
- InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
+ // Merge the combined block into the entry of the diamond.
+ MergeBlocks(BBI, *BBI1);
// If the if-converted block fallthrough or unconditionally branch into the
// tail block, and the tail block does not have other predecessors, then
// fold the tail block in as well.
+ BBInfo *CvtBBI = NeedBr1 ? BBI2 : &BBI;
if (BBI.TailBB &&
BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) {
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
@@ -687,11 +671,7 @@
TailBBI.Kind = ICDead;
}
- // Update block info. BB may be iteratively if-converted.
- if (OkToIfcvt) {
- BBI.Kind = ICReAnalyze;
- ReTryPreds(BBI.BB);
- }
+ // Update block info.
TrueBBI.Kind = ICDead;
FalseBBI.Kind = ICDead;
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