diff options
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 12 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/PhiBlockMerge.ll | 7 |
2 files changed, 16 insertions, 3 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index f0c97fd..1fbbb42 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1148,7 +1148,10 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { BasicBlock *BB = PN->getParent(); BasicBlock *IfTrue, *IfFalse; Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse); - if (!IfCond) return false; + if (!IfCond || + // Don't bother if the branch will be constant folded trivially. + isa<ConstantInt>(IfCond)) + return false; // Okay, we found that we can merge this two-entry phi node into a select. // Doing so would require us to fold *all* two entry phi nodes in this block. @@ -1243,6 +1246,13 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { NV->takeName(PN); PN->eraseFromParent(); } + + // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement + // has been flattened. Change DomBlock to jump directly to our new block to + // avoid other simplifycfg's kicking in on the diamond. + TerminatorInst *OldTI = DomBlock->getTerminator(); + BranchInst::Create(BB, OldTI); + OldTI->eraseFromParent(); return true; } diff --git a/test/Transforms/SimplifyCFG/PhiBlockMerge.ll b/test/Transforms/SimplifyCFG/PhiBlockMerge.ll index a648efd..c28d0ba 100644 --- a/test/Transforms/SimplifyCFG/PhiBlockMerge.ll +++ b/test/Transforms/SimplifyCFG/PhiBlockMerge.ll @@ -1,12 +1,14 @@ ; Test merging of blocks that only have PHI nodes in them ; -; RUN: opt < %s -simplifycfg -S | not grep N: +; RUN: opt < %s -simplifycfg -S | FileCheck %s ; define i32 @test(i1 %a, i1 %b) { -; <label>:0 +; CHECK: br i1 %a br i1 %a, label %M, label %O O: ; preds = %0 +; CHECK: select i1 %b, i32 0, i32 1 +; CHECK-NOT: phi br i1 %b, label %N, label %Q Q: ; preds = %O br label %N @@ -15,6 +17,7 @@ N: ; preds = %Q, %O %Wp = phi i32 [ 0, %O ], [ 1, %Q ] ; <i32> [#uses=1] br label %M M: ; preds = %N, %0 +; CHECK: %W = phi i32 %W = phi i32 [ %Wp, %N ], [ 2, %0 ] ; <i32> [#uses=1] %R = add i32 %W, 1 ; <i32> [#uses=1] ret i32 %R |