https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/106936
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 >From 0361a0460507780a90d8b60f2adc0ecab60d511a Mon Sep 17 00:00:00 2001 From: Yingwei Zheng <dtcxzyw2...@gmail.com> Date: Mon, 2 Sep 2024 10:51:58 +0800 Subject: [PATCH] [Clang][CodeGen] Don't emit assumptions if current block is unreachable. --- clang/lib/CodeGen/CGStmt.cpp | 2 +- clang/test/SemaCXX/cxx23-assume.cpp | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) 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))); +} +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
