[SimplifyLibCalls] Ignore nobuiltin/unavailable fortified libcalls.

ahmedbougacha · ahmedbougacha · commit 408d010a7cfc · 2015-04-01T00:45:09.000Z
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
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -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.
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/memset_chk-simplify-nobuiltin.ll b/llvm/test/Transforms/CodeGenPrepare/X86/memset_chk-simplify-nobuiltin.ll
@@ -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)
