Author: vedantk Date: Mon Oct 2 18:27:26 2017 New Revision: 314752 URL: http://llvm.org/viewvc/llvm-project?rev=314752&view=rev Log: [ubsan] Skip alignment checks which are folded away
Don't emit alignment checks which the IR constant folder throws away. I've tested this out on X86FastISel.cpp. While this doesn't decrease end-to-end compile-time significantly, it results in 122 fewer type checks (1% reduction) overall, without adding any real complexity. Differential Revision: https://reviews.llvm.org/D37544 Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp cfe/trunk/test/CodeGenCXX/ubsan-suppress-checks.cpp Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=314752&r1=314751&r2=314752&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGExpr.cpp (original) +++ cfe/trunk/lib/CodeGen/CGExpr.cpp Mon Oct 2 18:27:26 2017 @@ -618,6 +618,7 @@ void CodeGenFunction::EmitTypeCheck(Type auto PtrToAlloca = dyn_cast<llvm::AllocaInst>(Ptr->stripPointerCastsNoFollowAliases()); + llvm::Value *True = llvm::ConstantInt::getTrue(getLLVMContext()); llvm::Value *IsNonNull = nullptr; bool IsGuaranteedNonNull = SkippedChecks.has(SanitizerKind::Null) || PtrToAlloca; @@ -629,8 +630,7 @@ void CodeGenFunction::EmitTypeCheck(Type // The IR builder can constant-fold the null check if the pointer points to // a constant. - IsGuaranteedNonNull = - IsNonNull == llvm::ConstantInt::getTrue(getLLVMContext()); + IsGuaranteedNonNull = IsNonNull == True; // Skip the null check if the pointer is known to be non-null. if (!IsGuaranteedNonNull) { @@ -684,7 +684,8 @@ void CodeGenFunction::EmitTypeCheck(Type PtrAsInt, llvm::ConstantInt::get(IntPtrTy, AlignVal - 1)); llvm::Value *Aligned = Builder.CreateICmpEQ(Align, llvm::ConstantInt::get(IntPtrTy, 0)); - Checks.push_back(std::make_pair(Aligned, SanitizerKind::Alignment)); + if (Aligned != True) + Checks.push_back(std::make_pair(Aligned, SanitizerKind::Alignment)); } } Modified: cfe/trunk/test/CodeGenCXX/ubsan-suppress-checks.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/ubsan-suppress-checks.cpp?rev=314752&r1=314751&r2=314752&view=diff ============================================================================== --- cfe/trunk/test/CodeGenCXX/ubsan-suppress-checks.cpp (original) +++ cfe/trunk/test/CodeGenCXX/ubsan-suppress-checks.cpp Mon Oct 2 18:27:26 2017 @@ -17,6 +17,17 @@ void load_non_null_pointers() { // CHECK: ret void } +// CHECK-LABEL: define void @_Z31use_us16_aligned_array_elementsv +void use_us16_aligned_array_elements() { + static const unsigned short Arr[] = {0, 1, 2}; + auto use_array = [](const unsigned short(&X)[3]) -> void {}; + use_array(Arr); + + // CHECK-NOT: br i1 true + // ALIGN-NOT: call void @__ubsan_handle_type_mismatch + // CHECK: ret void +} + struct A { int foo; @@ -229,4 +240,5 @@ void force_irgen() { d->load_member_3(); load_non_null_pointers(); + use_us16_aligned_array_elements(); } _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
