Fix invalid calling convention used for libcalls on ARM.

ARM ABI specifies that all the libcalls use soft FP ABI 
(even hard FP binaries). These days clang emits _mulsc3 / _muldc3
calls with default (C) calling convention which would be translated
into AAPCS_VFP LLVM calling and thus the result of complex
multiplication will be bogus.

Introduce a way for a target to specify explicitly calling
convention for libcalls. Right now this is temporary correctness
fix. Ultimately, we'll end with intrinsic for complex 
multiplication and all calling convention decisions for libcalls
will be put into backend.

llvm-svn: 223123

clang/lib/CodeGen/ABIInfo.h

@@ -44,9 +44,12 @@ namespace clang {
     CodeGen::CodeGenTypes &CGT;
   protected:
     llvm::CallingConv::ID RuntimeCC;
+    llvm::CallingConv::ID BuiltinCC;
   public:
     ABIInfo(CodeGen::CodeGenTypes &cgt)
-      : CGT(cgt), RuntimeCC(llvm::CallingConv::C) {}
+      : CGT(cgt),
+        RuntimeCC(llvm::CallingConv::C),
+        BuiltinCC(llvm::CallingConv::C) {}
 
     virtual ~ABIInfo();
 
@@ -62,6 +65,11 @@ namespace clang {
       return RuntimeCC;
     }
 
+    /// Return the calling convention to use for compiler builtins
+    llvm::CallingConv::ID getBuiltinCC() const {
+      return BuiltinCC;
+    }
+
     virtual void computeInfo(CodeGen::CGFunctionInfo &FI) const = 0;
 
     /// EmitVAArg - Emit the target dependent code to load a value of

clang/lib/CodeGen/CGExprComplex.cpp

@@ -582,13 +582,22 @@ ComplexPairTy ComplexExprEmitter::EmitComplexBinOpLibCall(StringRef LibCallName,
            Op.Ty->castAs<ComplexType>()->getElementType());
 
   // We *must* use the full CG function call building logic here because the
-  // complex type has special ABI handling.
-  const CGFunctionInfo &FuncInfo = CGF.CGM.getTypes().arrangeFreeFunctionCall(
-      Op.Ty, Args, FunctionType::ExtInfo(), RequiredArgs::All);
+  // complex type has special ABI handling. We also should not forget about
+  // special calling convention which may be used for compiler builtins.
+  const CGFunctionInfo &FuncInfo =
+    CGF.CGM.getTypes().arrangeFreeFunctionCall(
+      Op.Ty, Args, FunctionType::ExtInfo(/* No CC here - will be added later */),
+      RequiredArgs::All);
   llvm::FunctionType *FTy = CGF.CGM.getTypes().GetFunctionType(FuncInfo);
-  llvm::Constant *Func = CGF.CGM.CreateRuntimeFunction(FTy, LibCallName);
+  llvm::Constant *Func = CGF.CGM.CreateBuiltinFunction(FTy, LibCallName);
+  llvm::Instruction *Call;
 
-  return CGF.EmitCall(FuncInfo, Func, ReturnValueSlot(), Args).getComplexVal();
+  RValue Res = CGF.EmitCall(FuncInfo, Func, ReturnValueSlot(), Args,
+                            nullptr, &Call);
+  cast<llvm::CallInst>(Call)->setCallingConv(CGF.CGM.getBuiltinCC());
+  cast<llvm::CallInst>(Call)->setDoesNotThrow();
+
+  return Res.getComplexVal();
 }
 
 /// \brief Lookup the libcall name for a given floating point type complex

clang/lib/CodeGen/CodeGenModule.cpp

@@ -109,6 +109,7 @@ CodeGenModule::CodeGenModule(ASTContext &C, const CodeGenOptions &CGO,
   Int8PtrPtrTy = Int8PtrTy->getPointerTo(0);
 
   RuntimeCC = getTargetCodeGenInfo().getABIInfo().getRuntimeCC();
+  BuiltinCC = getTargetCodeGenInfo().getABIInfo().getBuiltinCC();
 
   if (LangOpts.ObjC1)
     createObjCRuntime();
@@ -1656,6 +1657,21 @@ CodeGenModule::CreateRuntimeFunction(llvm::FunctionType *FTy,
   return C;
 }
 
+/// CreateBuiltinFunction - Create a new builtin function with the specified
+/// type and name.
+llvm::Constant *
+CodeGenModule::CreateBuiltinFunction(llvm::FunctionType *FTy,
+                                     StringRef Name,
+                                     llvm::AttributeSet ExtraAttrs) {
+  llvm::Constant *C =
+      GetOrCreateLLVMFunction(Name, FTy, GlobalDecl(), /*ForVTable=*/false,
+                              /*DontDefer=*/false, /*IsThunk=*/false, ExtraAttrs);
+  if (auto *F = dyn_cast<llvm::Function>(C))
+    if (F->empty())
+      F->setCallingConv(getBuiltinCC());
+  return C;
+}
+
 /// isTypeConstant - Determine whether an object of this type can be emitted
 /// as a constant.
 ///

clang/lib/CodeGen/CodeGenModule.h

@@ -150,6 +150,8 @@ struct CodeGenTypeCache {
 
   llvm::CallingConv::ID RuntimeCC;
   llvm::CallingConv::ID getRuntimeCC() const { return RuntimeCC; }
+  llvm::CallingConv::ID BuiltinCC;
+  llvm::CallingConv::ID getBuiltinCC() const { return BuiltinCC; }
 };
 
 struct RREntrypoints {
@@ -874,6 +876,11 @@ public:
                                         StringRef Name,
                                         llvm::AttributeSet ExtraAttrs =
                                           llvm::AttributeSet());
+  /// Create a new compiler builtin function with the specified type and name.
+  llvm::Constant *CreateBuiltinFunction(llvm::FunctionType *Ty,
+                                        StringRef Name,
+                                        llvm::AttributeSet ExtraAttrs =
+                                          llvm::AttributeSet());
   /// Create a new runtime global variable with the specified type and name.
   llvm::Constant *CreateRuntimeVariable(llvm::Type *Ty,
                                         StringRef Name);

clang/lib/CodeGen/TargetInfo.cpp

@@ -4330,7 +4330,7 @@ private:
 public:
   ARMABIInfo(CodeGenTypes &CGT, ABIKind _Kind) : ABIInfo(CGT), Kind(_Kind),
     NumVFPs(16), NumGPRs(4) {
-    setRuntimeCC();
+    setCCs();
     resetAllocatedRegs();
   }
 
@@ -4376,7 +4376,7 @@ private:
 
   llvm::CallingConv::ID getLLVMDefaultCC() const;
   llvm::CallingConv::ID getABIDefaultCC() const;
-  void setRuntimeCC();
+  void setCCs();
 
   void markAllocatedGPRs(unsigned Alignment, unsigned NumRequired) const;
   void markAllocatedVFPs(unsigned Alignment, unsigned NumRequired) const;
@@ -4535,7 +4535,7 @@ llvm::CallingConv::ID ARMABIInfo::getABIDefaultCC() const {
   llvm_unreachable("bad ABI kind");
 }
 
-void ARMABIInfo::setRuntimeCC() {
+void ARMABIInfo::setCCs() {
   assert(getRuntimeCC() == llvm::CallingConv::C);
 
   // Don't muddy up the IR with a ton of explicit annotations if
@@ -4543,6 +4543,9 @@ void ARMABIInfo::setRuntimeCC() {
   llvm::CallingConv::ID abiCC = getABIDefaultCC();
   if (abiCC != getLLVMDefaultCC())
     RuntimeCC = abiCC;
+
+  BuiltinCC = (getABIKind() == APCS ?
+               llvm::CallingConv::ARM_APCS : llvm::CallingConv::ARM_AAPCS);
 }
 
 /// markAllocatedVFPs - update VFPRegs according to the alignment and

clang/test/CodeGen/complex-math.c

@@ -2,6 +2,7 @@
 // RUN: %clang_cc1 %s -O1 -emit-llvm -triple x86_64-pc-win64 -o - | FileCheck %s --check-prefix=X86
 // RUN: %clang_cc1 %s -O1 -emit-llvm -triple i686-unknown-unknown -o - | FileCheck %s --check-prefix=X86
 // RUN: %clang_cc1 %s -O1 -emit-llvm -triple powerpc-unknown-unknown -o - | FileCheck %s --check-prefix=PPC
+// RUN: %clang_cc1 %s -O1 -emit-llvm -triple armv7-none-linux-gnueabihf -o - | FileCheck %s --check-prefix=ARM
 
 float _Complex add_float_rr(float a, float b) {
   // X86-LABEL: @add_float_rr(
@@ -471,3 +472,10 @@ _Bool ne_float_cc(float _Complex a, float _Complex b) {
   // X86: ret
   return a != b;
 }
+
+// Check that the libcall will obtain proper calling convention on ARM
+_Complex double foo(_Complex double a, _Complex double b) {
+  // ARM-LABEL: @foo(
+  // ARM: call arm_aapcscc { double, double } @__muldc3
+  return a*b;
+}