[clang] [clang][PowerPC] Add flag to enable compatibility with GNU for complex arguments (PR #77732)

[zhijian lin via cfe-commits]

================
@@ -337,12 +350,77 @@ CharUnits PPC32_SVR4_ABIInfo::getParamTypeAlignment(QualType Ty) const {
   return CharUnits::fromQuantity(4);
 }
 
+ABIArgInfo PPC32_SVR4_ABIInfo::handleComplex(QualType Ty,
+                                             uint64_t &TypeSize) const {
+
+  assert(Ty->isAnyComplexType());
+  llvm::Type *ElemTy;
+  unsigned SizeRegs;
+
+  if (TypeSize == 64) {
+    ElemTy = llvm::Type::getInt64Ty(getVMContext());
+    SizeRegs = 1;
+  } else {
+    ElemTy = llvm::Type::getInt32Ty(getVMContext());
+    SizeRegs = (TypeSize + 31) / 32;
+  }
+  return ABIArgInfo::getDirect(llvm::ArrayType::get(ElemTy, SizeRegs));
+}
+
+ABIArgInfo PPC32_SVR4_ABIInfo::classifyArgumentType(QualType Ty,
+                                                    int &ArgGPRsLeft) const {
+
+  assert(ArgGPRsLeft <= NumArgGPRs && "Arg GPR tracking underflow");
+  Ty = useFirstFieldIfTransparentUnion(Ty);
+
+  ASTContext &Context = getContext();
+
+  uint64_t TypeSize = Context.getTypeSize(Ty);
+
+  if (isComplexInRegABI && Ty->isAnyComplexType() &&
+      TypeSize <= RLen * ArgGPRsLeft) {
+    ArgGPRsLeft -= TypeSize / RLen;
+    return handleComplex(Ty, TypeSize);
+  }
+
+  if (isAggregateTypeForABI(Ty)) {
+    if (ArgGPRsLeft)
+      ArgGPRsLeft -= 1;
+    // Records with non-trivial destructors/copy-constructors should not be
+    // passed by value.
+    if (CGCXXABI::RecordArgABI RAA = getRecordArgABI(Ty, getCXXABI())) {
+      return getNaturalAlignIndirect(Ty, RAA == CGCXXABI::RAA_DirectInMemory);
+    }
+    return getNaturalAlignIndirect(Ty);
+  }
+
+  if (!Ty->isFloatingType()) {
+    if (TypeSize > RLen && TypeSize <= 2 * RLen)
+      ArgGPRsLeft -= 2;
+    else
+      ArgGPRsLeft--;
----------------
diggerlin wrote:

There is a bug here, you decrease the ArgGPRsLeft no mater whether ArgGPRsLeft >0;

I think you can put after `Ty = useFirstFieldIfTransparentUnion(Ty);`
```
Ty = useFirstFieldIfTransparentUnion(Ty);
if(Ty->isFloatingType()) return;
```
and change the code here as 
```
if(TypeSize <= RLen * ArgGPRsLeft) 
    ArgGPRsLeft -= TypeSize / RLen;
```

https://github.com/llvm/llvm-project/pull/77732