llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang-codegen Author: Yingwei Zheng (dtcxzyw) <details> <summary>Changes</summary> Fixes https://github.com/llvm/llvm-project/issues/106898. When emitting an infinite loop, clang codegen will delete the whole block and leave builder's current block as nullptr: https://github.com/llvm/llvm-project/blob/837ee5b46a5f7f898f0de7e46a19600b896a0a1f/clang/lib/CodeGen/CGStmt.cpp#L597-L600 Then clang will create `zext (icmp slt %a, %b)` without parent block for `a < b`. It will crash here: https://github.com/llvm/llvm-project/blob/837ee5b46a5f7f898f0de7e46a19600b896a0a1f/clang/lib/CodeGen/CGExprScalar.cpp#L416-L420 Even if we disabled this optimization, it still crashes in `Builder.CreateAssumption`: https://github.com/llvm/llvm-project/blob/837ee5b46a5f7f898f0de7e46a19600b896a0a1f/llvm/lib/IR/IRBuilder.cpp#L551-L561 This patch disables assumptions emission if current block is null. As an alternative, we can fix the optimization in `EmitIntToBoolConversion` and use `CGM.getIntrinsic` as we do for `__builtin_assume`: https://github.com/llvm/llvm-project/blob/837ee5b46a5f7f898f0de7e46a19600b896a0a1f/clang/lib/CodeGen/CGBuiltin.cpp#L3422-L3431 --- Full diff: https://github.com/llvm/llvm-project/pull/106936.diff 2 Files Affected: - (modified) clang/lib/CodeGen/CGStmt.cpp (+1-1) - (modified) clang/test/SemaCXX/cxx23-assume.cpp (+9) ``````````diff diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp index 7158a06e6bc3b3..b138c87a853495 100644 --- a/clang/lib/CodeGen/CGStmt.cpp +++ b/clang/lib/CodeGen/CGStmt.cpp @@ -752,7 +752,7 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) { } break; case attr::CXXAssume: { const Expr *Assumption = cast<CXXAssumeAttr>(A)->getAssumption(); - if (getLangOpts().CXXAssumptions && + if (getLangOpts().CXXAssumptions && Builder.GetInsertBlock() && !Assumption->HasSideEffects(getContext())) { llvm::Value *AssumptionVal = EvaluateExprAsBool(Assumption); Builder.CreateAssumption(AssumptionVal); diff --git a/clang/test/SemaCXX/cxx23-assume.cpp b/clang/test/SemaCXX/cxx23-assume.cpp index 9138501d726dd6..eeae59daea3f70 100644 --- a/clang/test/SemaCXX/cxx23-assume.cpp +++ b/clang/test/SemaCXX/cxx23-assume.cpp @@ -158,3 +158,12 @@ foo (int x, int y) return x + y; } } + +// Do not crash when assumptions are unreachable. +namespace gh106898 { +int foo () { + while(1); + int a = 0, b = 1; + __attribute__((assume (a < b))); +} +} `````````` </details> https://github.com/llvm/llvm-project/pull/106936 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
