[X86] Check if struct is blank before getting the inner types

[pengfei]

Summary

This fixes pr52011.

[LuoYuanke]

clang/test/CodeGen/X86/avx512fp16-abi.c

203

Add more cases for the struct composed of _Float16, float, double, struct {}?

[pengfei]

Add more tests. NFC.

[LuoYuanke]

clang/test/CodeGen/X86/avx512fp16-abi.c

207

Why not test CPP as well?

[pengfei]

clang/test/CodeGen/X86/avx512fp16-abi.c

207

CPP doesn't allow unnamed struct defined in the result type. I can change them to named struct.

[pengfei]

Use named struct to check CPP as well.

[LuoYuanke]

LGTM, thanks.

clang/lib/CodeGen/TargetInfo.cpp

 /// getFPTypeAtOffset - Return a floating point type at the specified offset.
 static llvm::Type *getFPTypeAtOffset(llvm::Type *IRType, unsigned IROffset,
                                      const llvm::DataLayout &TD) {
   if (IROffset == 0 && IRType->isFloatingPointTy())
     return IRType;
 
   // If this is a struct, recurse into the field at the specified offset.
   if (llvm::StructType *STy = dyn_cast<llvm::StructType>(IRType)) {
+    if (!STy->getNumContainedTypes())
+      return nullptr;
+
     const llvm::StructLayout *SL = TD.getStructLayout(STy);
     unsigned Elt = SL->getElementContainingOffset(IROffset);
     IROffset -= SL->getElementOffset(Elt);
     return getFPTypeAtOffset(STy->getElementType(Elt), IROffset, TD);
   }
 
   // If this is an array, recurse into the field at the specified offset.
   if (llvm::ArrayType *ATy = dyn_cast<llvm::ArrayType>(IRType)) {

clang/test/CodeGen/X86/avx512fp16-abi.c

struct halfs2 {
   struct {} s2;
 };
 
 _Float16 fs2(struct shalf2 s) {
   // CHECK-C: define{{.*}} @fs2(<2 x half>
   // CHECK-CPP: define{{.*}} @_Z3fs26shalf2(double {{.*}}
   return s.a;
 };
+
+#ifndef __cplusplus
+struct {
+  float a;
+  struct {};
+  double b
+} pr52011() {
+  // CHECK-C: define{{.*}} { float, double } @pr52011
+}
+#endif