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[SimplifyLibCalls] Ignore nobuiltin/unavailable fortified libcalls.

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We used to do this before refactorings around r225640.
Some clang users checked for _chk libcall availability using:
  __has_builtin(__builtin___memcpy_chk)
When compiling with -fno-builtin, this is always true.
When passing -ffreestanding/-mkernel, which both imply -fno-builtin, we
end up with fortified libcalls, which isn't acceptable in a freestanding
environment which only provides their non-fortified counterparts.

Until we change clang and/or teach external users to check for availability
differently, disregard the "nobuiltin" attribute and TLI::has.

Workaround for PR23093.

llvm-svn: 233776
This commit is contained in:
Ahmed Bougacha 2015-04-01 00:45:09 +00:00
parent 7bfde8133e
commit 8544aa4b2b
2 changed files with 31 additions and 3 deletions
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16
lib/Transforms/Utils/SimplifyLibCalls.cpp
View File

@ -2322,8 +2322,18 @@ Value *FortifiedLibCallSimplifier::optimizeStrpNCpyChk(CallInst *CI,
}
Value *FortifiedLibCallSimplifier::optimizeCall(CallInst *CI) {
if (CI->isNoBuiltin())
return nullptr;
// FIXME: We shouldn't be changing "nobuiltin" or TLI unavailable calls here.
// Some clang users checked for _chk libcall availability using:
// __has_builtin(__builtin___memcpy_chk)
// When compiling with -fno-builtin, this is always true.
// When passing -ffreestanding/-mkernel, which both imply -fno-builtin, we
// end up with fortified libcalls, which isn't acceptable in a freestanding
// environment which only provides their non-fortified counterparts.
//
// Until we change clang and/or teach external users to check for availability
// differently, disregard the "nobuiltin" attribute and TLI::has.
//
// PR23093.
LibFunc::Func Func;
Function *Callee = CI->getCalledFunction();
@ -2332,7 +2342,7 @@ Value *FortifiedLibCallSimplifier::optimizeCall(CallInst *CI) {
bool isCallingConvC = CI->getCallingConv() == llvm::CallingConv::C;
// First, check that this is a known library functions.
if (!TLI->getLibFunc(FuncName, Func) || !TLI->has(Func))
if (!TLI->getLibFunc(FuncName, Func))
return nullptr;
// We never change the calling convention.

18
test/Transforms/CodeGenPrepare/X86/memset_chk-simplify-nobuiltin.ll Normal file
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@ -0,0 +1,18 @@
; RUN: opt -S -disable-simplify-libcalls -codegenprepare < %s | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
; This is a workaround for PR23093: when building with -mkernel/-fno-builtin,
; we still generate fortified library calls.
; Check that we ignore two things:
; - attribute nobuiltin
; - TLI::has (always returns false thanks to -disable-simplify-libcalls)
; CHECK-NOT: _chk
; CHECK: call void @llvm.memset.p0i8.i64(i8* %dst, i8 0, i64 %len, i32 1, i1 false)
define void @test_nobuiltin(i8* %dst, i64 %len) {
call i8* @__memset_chk(i8* %dst, i32 0, i64 %len, i64 -1) nobuiltin
ret void
}
declare i8* @__memset_chk(i8*, i32, i64, i64)