From 3d6f49a56995b845c40be5827ded5d1e3f692cec Mon Sep 17 00:00:00 2001 From: serge-sans-paille Date: Thu, 16 Sep 2021 18:13:15 +0200 Subject: [PATCH] Simplify handling of builtin with inline redefinition It is a common practice in glibc header to provide an inline redefinition of an existing function. It is especially the case for fortified function. Clang currently has an imperfect approach to the problem, using a combination of trivially recursive function detection and noinline attribute. Simplify the logic by suffixing these functions by `.inline` during codegen, so that they are not recognized as builtin by llvm. After that patch, clang passes all tests from https://github.com/serge-sans-paille/fortify-test-suite Differential Revision: https://reviews.llvm.org/D109967 --- clang/lib/CodeGen/CodeGenFunction.cpp | 5 +++ clang/lib/CodeGen/CodeGenModule.cpp | 5 +++ clang/test/CodeGen/memcpy-inline-builtin.c | 44 +++++++++++++++++++ .../memcpy-no-nobuiltin-if-not-emitted.c | 25 ----------- clang/test/CodeGen/memcpy-nobuiltin.c | 3 +- clang/test/CodeGen/pr9614.c | 4 +- 6 files changed, 58 insertions(+), 28 deletions(-) create mode 100644 clang/test/CodeGen/memcpy-inline-builtin.c delete mode 100644 clang/test/CodeGen/memcpy-no-nobuiltin-if-not-emitted.c diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index 5f63461aea96..fbb06885ba35 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -1301,6 +1301,11 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, FunctionArgList Args; QualType ResTy = BuildFunctionArgList(GD, Args); + // Give a different name to inline builtin to avoid conflict with actual + // builtins. + if (FD->isInlineBuiltinDeclaration() && Fn) + Fn->setName(Fn->getName() + ".inline"); + // Check if we should generate debug info for this function. if (FD->hasAttr()) { // Clear non-distinct debug info that was possibly attached to the function diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 9715657b4c6e..83418014f0b5 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -3169,6 +3169,11 @@ bool CodeGenModule::shouldEmitFunction(GlobalDecl GD) { } } + // Inline builtins declaration must be emitted. They often are fortified + // functions. + if (F->isInlineBuiltinDeclaration()) + return true; + // PR9614. Avoid cases where the source code is lying to us. An available // externally function should have an equivalent function somewhere else, // but a function that calls itself through asm label/`__builtin_` trickery is diff --git a/clang/test/CodeGen/memcpy-inline-builtin.c b/clang/test/CodeGen/memcpy-inline-builtin.c new file mode 100644 index 000000000000..814ce220195f --- /dev/null +++ b/clang/test/CodeGen/memcpy-inline-builtin.c @@ -0,0 +1,44 @@ +// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py + +// RUN: %clang_cc1 -triple x86_64 -S -emit-llvm -o - %s | FileCheck %s +// +// Verifies that clang detects memcpy inline version and uses it instead of the builtin. + +typedef unsigned long size_t; + +// Clang requires these attributes for a function to be redefined. +#define AVAILABLE_EXTERNALLY extern inline __attribute__((always_inline)) __attribute__((gnu_inline)) + +// Clang recognizes an inline builtin and renames it to prevent conflict with builtins. +AVAILABLE_EXTERNALLY void *memcpy(void *a, const void *b, size_t c) { + asm("# memcpy.inline marker"); + return __builtin_memcpy(a, b, c); +} + +// CHECK-LABEL: @foo( +// CHECK-NEXT: entry: +// CHECK-NEXT: [[A_ADDR_I:%.*]] = alloca i8*, align 8 +// CHECK-NEXT: [[B_ADDR_I:%.*]] = alloca i8*, align 8 +// CHECK-NEXT: [[C_ADDR_I:%.*]] = alloca i64, align 8 +// CHECK-NEXT: [[A_ADDR:%.*]] = alloca i8*, align 8 +// CHECK-NEXT: [[B_ADDR:%.*]] = alloca i8*, align 8 +// CHECK-NEXT: [[C_ADDR:%.*]] = alloca i64, align 8 +// CHECK-NEXT: store i8* [[A:%.*]], i8** [[A_ADDR]], align 8 +// CHECK-NEXT: store i8* [[B:%.*]], i8** [[B_ADDR]], align 8 +// CHECK-NEXT: store i64 [[C:%.*]], i64* [[C_ADDR]], align 8 +// CHECK-NEXT: [[TMP0:%.*]] = load i8*, i8** [[A_ADDR]], align 8 +// CHECK-NEXT: [[TMP1:%.*]] = load i8*, i8** [[B_ADDR]], align 8 +// CHECK-NEXT: [[TMP2:%.*]] = load i64, i64* [[C_ADDR]], align 8 +// CHECK-NEXT: store i8* [[TMP0]], i8** [[A_ADDR_I]], align 8 +// CHECK-NEXT: store i8* [[TMP1]], i8** [[B_ADDR_I]], align 8 +// CHECK-NEXT: store i64 [[TMP2]], i64* [[C_ADDR_I]], align 8 +// CHECK-NEXT: call void asm sideeffect "# memcpy.inline marker", "~{dirflag},~{fpsr},~{flags}"() #[[ATTR2:[0-9]+]], !srcloc !2 +// CHECK-NEXT: [[TMP3:%.*]] = load i8*, i8** [[A_ADDR_I]], align 8 +// CHECK-NEXT: [[TMP4:%.*]] = load i8*, i8** [[B_ADDR_I]], align 8 +// CHECK-NEXT: [[TMP5:%.*]] = load i64, i64* [[C_ADDR_I]], align 8 +// CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 1 [[TMP3]], i8* align 1 [[TMP4]], i64 [[TMP5]], i1 false) #[[ATTR2]] +// CHECK-NEXT: ret void +// +void foo(void *a, const void *b, size_t c) { + memcpy(a, b, c); +} diff --git a/clang/test/CodeGen/memcpy-no-nobuiltin-if-not-emitted.c b/clang/test/CodeGen/memcpy-no-nobuiltin-if-not-emitted.c deleted file mode 100644 index d3a219a972d3..000000000000 --- a/clang/test/CodeGen/memcpy-no-nobuiltin-if-not-emitted.c +++ /dev/null @@ -1,25 +0,0 @@ -// RUN: %clang_cc1 -triple x86_64-unknown-unknown -S -emit-llvm -o - %s | FileCheck %s -// -// Verifies that clang doesn't mark an inline builtin definition as `nobuiltin` -// if the builtin isn't emittable. - -typedef unsigned long size_t; - -// always_inline is used so clang will emit this body. Otherwise, we need >= -// -O1. -#define AVAILABLE_EXTERNALLY extern inline __attribute__((always_inline)) \ - __attribute__((gnu_inline)) - -AVAILABLE_EXTERNALLY void *memcpy(void *a, const void *b, size_t c) { - return __builtin_memcpy(a, b, c); -} - -// CHECK-LABEL: define{{.*}} void @foo -void foo(void *a, const void *b, size_t c) { - // Clang will always _emit_ this as memcpy. LLVM turns it into @llvm.memcpy - // later on if optimizations are enabled. - // CHECK: call i8* @memcpy - memcpy(a, b, c); -} - -// CHECK-NOT: nobuiltin diff --git a/clang/test/CodeGen/memcpy-nobuiltin.c b/clang/test/CodeGen/memcpy-nobuiltin.c index fb51d87413a1..cbd0ccaa2ebb 100644 --- a/clang/test/CodeGen/memcpy-nobuiltin.c +++ b/clang/test/CodeGen/memcpy-nobuiltin.c @@ -4,7 +4,8 @@ // // CHECK-WITH-DECL-NOT: @llvm.memcpy // CHECK-NO-DECL: @llvm.memcpy -// CHECK-SELF-REF-DECL: @llvm.memcpy +// CHECK-SELF-REF-DECL-LABEL: define dso_local i8* @memcpy.inline +// CHECK-SELF-REF-DECL: @memcpy( // #include void test(void *dest, void const *from, size_t n) { diff --git a/clang/test/CodeGen/pr9614.c b/clang/test/CodeGen/pr9614.c index c153283a8377..3674ba844aa1 100644 --- a/clang/test/CodeGen/pr9614.c +++ b/clang/test/CodeGen/pr9614.c @@ -32,14 +32,14 @@ void f(void) { // CHECK-LABEL: define{{.*}} void @f() // CHECK: call void @foo() -// CHECK: call i32 @abs(i32 0) +// CHECK: call i32 @abs(i32 %0) // CHECK: call i8* @strrchr( // CHECK: call void @llvm.prefetch.p0i8( // CHECK: call i8* @memchr( // CHECK: ret void // CHECK: declare void @foo() -// CHECK: declare i32 @abs(i32 // CHECK: declare i8* @strrchr(i8*, i32) // CHECK: declare i8* @memchr( +// CHECK: declare i32 @abs(i32 // CHECK: declare void @llvm.prefetch.p0i8(