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1) Use the new SimplifyInstructionsInBlock routine instead of the copy

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in JT.

2) When cloning blocks for PHI or xor conditions, use
instsimplify to simplify the code as we go.  This allows us to 
squish common cases early in JT which opens up opportunities for
subsequent iterations, and allows it to completely simplify the
testcase.

llvm-svn: 93253
This commit is contained in:
Chris Lattner 2010-01-12 20:41:47 +00:00
parent 87f86498c3
commit 21bbaf49d5
2 changed files with 15 additions and 23 deletions
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31
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -1341,20 +1341,7 @@ bool JumpThreading::ThreadEdge(BasicBlock *BB,
// At this point, the IR is fully up to date and consistent. Do a quick scan
// over the new instructions and zap any that are constants or dead. This
// frequently happens because of phi translation.
BI = NewBB->begin();
for (BasicBlock::iterator E = NewBB->end(); BI != E; ) {
Instruction *Inst = BI++;
if (Value *V = SimplifyInstruction(Inst, TD)) {
WeakVH BIHandle(BI);
ReplaceAndSimplifyAllUses(Inst, V, TD);
if (BIHandle == 0)
BI = NewBB->begin();
continue;
}
RecursivelyDeleteTriviallyDeadInstructions(Inst);
}
SimplifyInstructionsInBlock(NewBB, TD);
// Threaded an edge!
++NumThreads;
@ -1425,9 +1412,6 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
// mapping and using it to remap operands in the cloned instructions.
for (; BI != BB->end(); ++BI) {
Instruction *New = BI->clone();
New->setName(BI->getName());
PredBB->getInstList().insert(OldPredBranch, New);
ValueMapping[BI] = New;
// Remap operands to patch up intra-block references.
for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
@ -1436,6 +1420,19 @@ bool JumpThreading::DuplicateCondBranchOnPHIIntoPred(BasicBlock *BB,
if (I != ValueMapping.end())
New->setOperand(i, I->second);
}
// If this instruction can be simplified after the operands are updated,
// just use the simplified value instead. This frequently happens due to
// phi translation.
if (Value *IV = SimplifyInstruction(New, TD)) {
delete New;
ValueMapping[BI] = IV;
} else {
// Otherwise, insert the new instruction into the block.
New->setName(BI->getName());
PredBB->getInstList().insert(OldPredBranch, New);
ValueMapping[BI] = New;
}
}
// Check to see if the targets of the branch had PHI nodes. If so, we need to

7
test/Transforms/JumpThreading/basic.ll
View File

@ -407,12 +407,7 @@ T2:
F2:
ret i32 %v1
;; FIXME: CONSTANT FOLD on clone and when phi gets eliminated.
; CHECK: Entry.Merge_crit_edge:
; CHECK-NEXT: %M1 = icmp eq i32 192, 192
; CHECK-NEXT: %N2 = xor i1 true, %M1
; CHECK-NEXT: br i1 %N2, label %T2, label %F2
; CHECK: br i1 %cond, label %F2, label %Merge
; CHECK: Merge:
; CHECK-NEXT: %M = icmp eq i32 %v1, 192