[clang] 909a851 - [CGAtomic] Mark atomic libcall functions `nounwind`

[Gui Andrade via cfe-commits]

Author: Gui Andrade
Date: 2020-08-14T07:46:43Z
New Revision: 909a851dbffeb3637c19268e12e10fdf3dae2add

URL: https://github.com/llvm/llvm-project/commit/909a851dbffeb3637c19268e12e10fdf3dae2add
DIFF: https://github.com/llvm/llvm-project/commit/909a851dbffeb3637c19268e12e10fdf3dae2add.diff

LOG: [CGAtomic] Mark atomic libcall functions `nounwind`

These functions won't ever unwind. This is useful for MemorySanitizer
as it simplifies handling __atomic_load in particular.

Differential Revision: https://reviews.llvm.org/D85573

Added: 
    

Modified: 
    clang/lib/CodeGen/CGAtomic.cpp
    clang/test/CodeGen/atomic_ops.c

Removed: 
    


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diff  --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index b7ada4ac7e3b..d7720a23dd72 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -307,7 +307,14 @@ static RValue emitAtomicLibcall(CodeGenFunction &CGF,
   const CGFunctionInfo &fnInfo =
     CGF.CGM.getTypes().arrangeBuiltinFunctionCall(resultType, args);
   llvm::FunctionType *fnTy = CGF.CGM.getTypes().GetFunctionType(fnInfo);
-  llvm::FunctionCallee fn = CGF.CGM.CreateRuntimeFunction(fnTy, fnName);
+  llvm::AttrBuilder fnAttrB;
+  fnAttrB.addAttribute(llvm::Attribute::NoUnwind);
+  fnAttrB.addAttribute(llvm::Attribute::WillReturn);
+  llvm::AttributeList fnAttrs = llvm::AttributeList::get(
+      CGF.getLLVMContext(), llvm::AttributeList::FunctionIndex, fnAttrB);
+
+  llvm::FunctionCallee fn =
+      CGF.CGM.CreateRuntimeFunction(fnTy, fnName, fnAttrs);
   auto callee = CGCallee::forDirect(fn);
   return CGF.EmitCall(fnInfo, callee, ReturnValueSlot(), args);
 }

diff  --git a/clang/test/CodeGen/atomic_ops.c b/clang/test/CodeGen/atomic_ops.c
index c1eb1d005dba..79a1e5dba780 100644
--- a/clang/test/CodeGen/atomic_ops.c
+++ b/clang/test/CodeGen/atomic_ops.c
@@ -26,6 +26,9 @@ void foo(int x)
 
 }
 
+// LIBCALL: declare void @__atomic_load(i32, i8*, i8*, i32) [[LC_ATTRS:#[0-9]+]]
+// LIBCALL: declare i1 @__atomic_compare_exchange(i32, i8*, i8*, i8*, i32, i32) [[LC_ATTRS:#[0-9]+]]
+
 extern _Atomic _Bool b;
 
 _Bool bar() {
@@ -53,6 +56,8 @@ void baz(int y) {
   x += y;
 }
 
+// LIBCALL: declare void @__atomic_store(i32, i8*, i8*, i32) [[LC_ATTRS:#[0-9]+]]
+
 _Atomic(int) compound_add(_Atomic(int) in) {
 // CHECK-LABEL: @compound_add
 // CHECK: [[OLD:%.*]] = atomicrmw add i32* {{.*}}, i32 5 seq_cst
@@ -107,3 +112,5 @@ _Atomic(int) compound_mul(_Atomic(int) in) {
 
   return (in *= 5);
 }
+
+// LIBCALL: [[LC_ATTRS]] = { nounwind willreturn }