Author: Roman Lebedev Date: 2021-01-06T01:52:36+03:00 New Revision: 29ca7d5a1ad968c371124b8d82edd8d91eee7b4f
URL: https://github.com/llvm/llvm-project/commit/29ca7d5a1ad968c371124b8d82edd8d91eee7b4f DIFF: https://github.com/llvm/llvm-project/commit/29ca7d5a1ad968c371124b8d82edd8d91eee7b4f.diff LOG: [SimplifyCFG] simplifyUnreachable(): fix handling of degenerate same-destination conditional branch One would hope that it would have been already canonicalized into an unconditional branch, but that isn't really guaranteed to happen with SimplifyCFG's visitation order. Added: Modified: llvm/lib/Transforms/Utils/SimplifyCFG.cpp llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll Removed: ################################################################################ diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index cf4854d27f4a..7921a7462e2d 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -4683,16 +4683,18 @@ bool SimplifyCFGOpt::simplifyUnreachable(UnreachableInst *UI) { Instruction *TI = Predecessor->getTerminator(); IRBuilder<> Builder(TI); if (auto *BI = dyn_cast<BranchInst>(TI)) { - if (BI->isUnconditional()) { - assert(BI->getSuccessor(0) == BB && "Incorrect CFG"); + // We could either have a proper unconditional branch, + // or a degenerate conditional branch with matching destinations. + if (all_of(BI->successors(), + [BB](auto *Successor) { return Successor == BB; })) { new UnreachableInst(TI->getContext(), TI); TI->eraseFromParent(); Changed = true; } else { + assert(BI->isConditional() && "Can't get here with an uncond branch."); Value* Cond = BI->getCondition(); - // assert(BI->getSuccessor(0) != BI->getSuccessor(1) && - // "Same-destination conditional branch instruction was " - // "already canonicalized into an unconditional branch."); + assert(BI->getSuccessor(0) != BI->getSuccessor(1) && + "The destinations are guaranteed to be diff erent here."); if (BI->getSuccessor(0) == BB) { Builder.CreateAssumption(Builder.CreateNot(Cond)); Builder.CreateBr(BI->getSuccessor(1)); diff --git a/llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll b/llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll index b56d9d435925..66218a10521b 100644 --- a/llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll +++ b/llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll @@ -1,5 +1,5 @@ ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py -; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=0 < %s | FileCheck %s +; RUN: opt -S -simplifycfg -simplifycfg-require-and-preserve-domtree=1 < %s | FileCheck %s @global = external global i16, align 1 @global.1 = external global i16, align 1 @@ -11,14 +11,6 @@ define void @widget() { ; CHECK-NEXT: [[I:%.*]] = load i16, i16* @global, align 1 ; CHECK-NEXT: [[I13:%.*]] = icmp ne i16 [[I]], 0 ; CHECK-NEXT: call void @llvm.assume(i1 [[I13]]) -; CHECK-NEXT: [[I17:%.*]] = load i16, i16* @global, align 1 -; CHECK-NEXT: [[I18:%.*]] = sdiv i16 2, [[I17]] -; CHECK-NEXT: [[I19:%.*]] = icmp ne i16 [[I18]], 0 -; CHECK-NEXT: [[I20:%.*]] = zext i1 [[I19]] to i16 -; CHECK-NEXT: [[I21:%.*]] = load i16, i16* @global.1, align 1 -; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[I19]], i16 [[I20]], i16 [[I21]] -; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[I19]], true -; CHECK-NEXT: call void @llvm.assume(i1 [[TMP0]]) ; CHECK-NEXT: unreachable ; bb: _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
