[llvm-commits] [llvm] r69102 - in /llvm/trunk: lib/Transforms/Scalar/CondPropagate.cpp test/Transforms/CondProp/phisimplify3.ll
Evan Cheng
evan.cheng at apple.com
Tue Apr 14 17:45:05 PDT 2009
Thanks. Fixed.
Evan
On Apr 14, 2009, at 5:14 PM, Chris Lattner wrote:
>
> On Apr 14, 2009, at 4:40 PM, Evan Cheng wrote:
>
>> Author: evancheng
>> Date: Tue Apr 14 18:40:03 2009
>> New Revision: 69102
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=69102&view=rev
>> Log:
>> Optimize conditional branch on i1 phis with non-constant inputs.
>>
>> This turns:
>>
>> eq:
>> %3 = icmp eq i32 %1, %2
>> br label %join
>>
>> ne:
>> %4 = icmp ne i32 %1, %2
>> br label %join
>>
>> join:
>> %5 = phi i1 [%3, %eq], [%4, %ne]
>> br i1 %5, label %yes, label %no
>
> Cool. I didn't scrutinize the code, but does this handle the case (or
> avoid transforming) when "yes" or "no" have phi nodes? This will add
> new preds, so phi nodes in them would need to be updated.
>
> -Chris
>
>>
>>
>> =>
>>
>> eq:
>> %3 = icmp eq i32 %1, %2
>> br i1 %3, label %yes, label %no
>>
>> ne:
>> %4 = icmp ne i32 %1, %2
>> br i1 %4, label %yes, label %no
>>
>> Added:
>> llvm/trunk/test/Transforms/CondProp/phisimplify3.ll
>> Modified:
>> llvm/trunk/lib/Transforms/Scalar/CondPropagate.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Scalar/CondPropagate.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CondPropagate.cpp?rev=69102&r1=69101&r2=69102&view=diff
>>
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =====================================================================
>> --- llvm/trunk/lib/Transforms/Scalar/CondPropagate.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/CondPropagate.cpp Tue Apr 14
>> 18:40:03 2009
>> @@ -51,6 +51,7 @@
>> void SimplifyPredecessors(BranchInst *BI);
>> void SimplifyPredecessors(SwitchInst *SI);
>> void RevectorBlockTo(BasicBlock *FromBB, BasicBlock *ToBB);
>> + bool RevectorBlockTo(BasicBlock *FromBB, Value *Cond,
>> BranchInst *BI);
>> };
>> }
>>
>> @@ -160,20 +161,19 @@
>> // Ok, we have this really simple case, walk the PHI operands,
>> looking for
>> // constants. Walk from the end to remove operands from the end
>> when
>> // possible, and to avoid invalidating "i".
>> - for (unsigned i = PN->getNumIncomingValues(); i != 0; --i)
>> - if (ConstantInt *CB = dyn_cast<ConstantInt>(PN-
>>> getIncomingValue(i-1))) {
>> - // If we have a constant, forward the edge from its current
>> to its
>> - // ultimate destination.
>> - RevectorBlockTo(PN->getIncomingBlock(i-1),
>> - BI->getSuccessor(CB->isZero()));
>> - ++NumBrThread;
>> -
>> - // If there were two predecessors before this simplification,
>> or if the
>> - // PHI node contained all the same value except for the one
>> we just
>> - // substituted, the PHI node may be deleted. Don't iterate
>> through it the
>> - // last time.
>> - if (BI->getCondition() != PN) return;
>> - }
>> + for (unsigned i = PN->getNumIncomingValues(); i != 0; --i) {
>> + Value *InVal = PN->getIncomingValue(i-1);
>> + if (!RevectorBlockTo(PN->getIncomingBlock(i-1), InVal, BI))
>> + continue;
>> +
>> + ++NumBrThread;
>> +
>> + // If there were two predecessors before this simplification,
>> or if the
>> + // PHI node contained all the same value except for the one we
>> just
>> + // substituted, the PHI node may be deleted. Don't iterate
>> through it the
>> + // last time.
>> + if (BI->getCondition() != PN) return;
>> + }
>> }
>>
>> // SimplifyPredecessors(switch) - We know that SI is switch based on
>> a PHI node
>> @@ -242,3 +242,44 @@
>>
>> MadeChange = true;
>> }
>> +
>> +bool CondProp::RevectorBlockTo(BasicBlock *FromBB, Value *Cond,
>> BranchInst *BI){
>> + BranchInst *FromBr = cast<BranchInst>(FromBB->getTerminator());
>> + if (!FromBr->isUnconditional())
>> + return false;
>> +
>> + // Get the old block we are threading through.
>> + BasicBlock *OldSucc = FromBr->getSuccessor(0);
>> +
>> + // If the condition is a constant, simply revector the
>> unconditional branch at
>> + // the end of FromBB to one of the successors of its current
>> successor.
>> + if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) {
>> + BasicBlock *ToBB = BI->getSuccessor(CB->isZero());
>> +
>> + // OldSucc had multiple successors. If ToBB has multiple
>> predecessors, then
>> + // the edge between them would be critical, which we already
>> took care of.
>> + // If ToBB has single operand PHI node then take care of it
>> here.
>> + FoldSingleEntryPHINodes(ToBB);
>> +
>> + // Update PHI nodes in OldSucc to know that FromBB no longer
>> branches to it.
>> + OldSucc->removePredecessor(FromBB);
>> +
>> + // Change FromBr to branch to the new destination.
>> + FromBr->setSuccessor(0, ToBB);
>> + } else {
>> + // Insert the new conditional branch.
>> + BranchInst::Create(BI->getSuccessor(0), BI->getSuccessor(1),
>> Cond, FromBr);
>> +
>> + FoldSingleEntryPHINodes(BI->getSuccessor(0));
>> + FoldSingleEntryPHINodes(BI->getSuccessor(1));
>> +
>> + // Update PHI nodes in OldSucc to know that FromBB no longer
>> branches to it.
>> + OldSucc->removePredecessor(FromBB);
>> +
>> + // Delete the old branch.
>> + FromBr->eraseFromParent();
>> + }
>> +
>> + MadeChange = true;
>> + return true;
>> +}
>>
>> Added: llvm/trunk/test/Transforms/CondProp/phisimplify3.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CondProp/phisimplify3.ll?rev=69102&view=auto
>>
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =====================================================================
>> --- llvm/trunk/test/Transforms/CondProp/phisimplify3.ll (added)
>> +++ llvm/trunk/test/Transforms/CondProp/phisimplify3.ll Tue Apr 14
>> 18:40:03 2009
>> @@ -0,0 +1,26 @@
>> +; RUN: llvm-as < %s | opt -condprop | llvm-dis | not grep phi
>> +
>> +define i32 @foo(i1, i32, i32) {
>> +prologue:
>> + br i1 %0, label %eq, label %ne
>> +
>> +eq: ; preds = %prologue
>> + store i32 0, i32* inttoptr (i32 10000 to i32*)
>> + %3 = icmp eq i32 %1, %2 ; <i1> [#uses=1]
>> + br label %join
>> +
>> +ne: ; preds = %prologue
>> + %4 = icmp ne i32 %1, %2 ; <i1> [#uses=1]
>> + br label %join
>> +
>> +join: ; preds = %ne, %eq
>> + %5 = phi i1 [ %3, %eq ], [ %4, %ne ] ; <i1> [#uses=1]
>> + br i1 %5, label %yes, label %no
>> +
>> +yes: ; preds = %join
>> + store i32 0, i32* inttoptr (i32 20000 to i32*)
>> + ret i32 5
>> +
>> +no: ; preds = %join
>> + ret i32 20
>> +}
>>
>>
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