diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index 06fbaad3e48b..2d5773a31fc7 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -538,9 +538,11 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { if (!PN->hasOneUse()) { // Walk the use list for the instruction, comparing them to I. for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); - UI != E; ++UI) - if (!I.isIdenticalTo(cast(*UI))) + UI != E; ++UI) { + Instruction *User = cast(*UI); + if (User != &I && !I.isIdenticalTo(User)) return 0; + } // Otherwise, we can replace *all* users with the new PHI we form. } @@ -565,6 +567,12 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { if (InvokeInst *II = dyn_cast(InVal)) if (II->getParent() == NonConstBB) return 0; + + // If the incoming non-constant value is in I's block, we will remove one + // instruction, but insert another equivalent one, leading to infinite + // instcombine. + if (NonConstBB == I.getParent()) + return 0; } // If there is exactly one non-constant value, we can insert a copy of the diff --git a/llvm/test/Transforms/InstCombine/crash.ll b/llvm/test/Transforms/InstCombine/crash.ll index e8babc3a1ee3..e17774d7b0e2 100644 --- a/llvm/test/Transforms/InstCombine/crash.ll +++ b/llvm/test/Transforms/InstCombine/crash.ll @@ -353,3 +353,20 @@ entry: ret %struct.basic_ios* %0 } +; PR9013 +define void @test18() nounwind ssp { +entry: + br label %for.cond + +for.cond: ; preds = %for.inc, %entry + %l_197.0 = phi i32 [ 0, %entry ], [ %sub.i, %for.inc ] + br label %for.inc + +for.inc: ; preds = %for.cond + %conv = and i32 %l_197.0, 255 + %sub.i = add nsw i32 %conv, -1 + br label %for.cond + +return: ; No predecessors! + ret void +}