[CodeGen][ARM] Fix FP16 vector coercion

Summary:
When a function argument or return type is a homogeneous aggregate
which contains an FP16 vector but the target does not support FP16
operations natively, the type must be converted into an array of
integer vectors by then front end (otherwise LLVM will handle FP16
vectors incorrectly by scalarizing them and promoting FP16 to float,
see https://reviews.llvm.org/D50507).

Currently the logic for checking whether or not a given homogeneous
aggregate contains FP16 vectors is incorrect: it only looks at the
type of the first vector.

This patch fixes the issue by adding a new method
ARMABIInfo::containsAnyFP16Vectors and using it. The traversal logic
of this method is largely the same as in
ABIInfo::isHomogeneousAggregate.

Reviewers: eli.friedman, olista01, ostannard

Reviewed By: ostannard

Subscribers: ostannard, john.brawn, javed.absar, kristof.beyls, pbarrio, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63437

llvm-svn: 363687

1 files changed, 33 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 4ef57786f44..707425ea813 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -5607,6 +5607,7 @@ private:
                                           uint64_t Members) const;
   ABIArgInfo coerceIllegalVector(QualType Ty) const;
   bool isIllegalVectorType(QualType Ty) const;
+  bool containsAnyFP16Vectors(QualType Ty) const;
 
   bool isHomogeneousAggregateBaseType(QualType Ty) const override;
   bool isHomogeneousAggregateSmallEnough(const Type *Ty,
@@ -5806,9 +5807,7 @@ ABIArgInfo ARMABIInfo::classifyHomogeneousAggregate(QualType Ty,
   // Base can be a floating-point or a vector.
   if (const VectorType *VT = Base->getAs<VectorType>()) {
     // FP16 vectors should be converted to integer vectors
-    if (!getTarget().hasLegalHalfType() &&
-        (VT->getElementType()->isFloat16Type() ||
-          VT->getElementType()->isHalfType())) {
+    if (!getTarget().hasLegalHalfType() && containsAnyFP16Vectors(Ty)) {
       uint64_t Size = getContext().getTypeSize(VT);
       llvm::Type *NewVecTy = llvm::VectorType::get(
           llvm::Type::getInt32Ty(getVMContext()), Size / 32);
@@ -6169,6 +6168,37 @@ bool ARMABIInfo::isIllegalVectorType(QualType Ty) const {
   return false;
 }
 
+/// Return true if a type contains any 16-bit floating point vectors
+bool ARMABIInfo::containsAnyFP16Vectors(QualType Ty) const {
+  if (const ConstantArrayType *AT = getContext().getAsConstantArrayType(Ty)) {
+    uint64_t NElements = AT->getSize().getZExtValue();
+    if (NElements == 0)
+      return false;
+    return containsAnyFP16Vectors(AT->getElementType());
+  } else if (const RecordType *RT = Ty->getAs<RecordType>()) {
+    const RecordDecl *RD = RT->getDecl();
+
+    // If this is a C++ record, check the bases first.
+    if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD))
+      if (llvm::any_of(CXXRD->bases(), [this](const CXXBaseSpecifier &B) {
+            return containsAnyFP16Vectors(B.getType());
+          }))
+        return true;
+
+    if (llvm::any_of(RD->fields(), [this](FieldDecl *FD) {
+          return FD && containsAnyFP16Vectors(FD->getType());
+        }))
+      return true;
+
+    return false;
+  } else {
+    if (const VectorType *VT = Ty->getAs<VectorType>())
+      return (VT->getElementType()->isFloat16Type() ||
+              VT->getElementType()->isHalfType());
+    return false;
+  }
+}
+
 bool ARMABIInfo::isLegalVectorTypeForSwift(CharUnits vectorSize,
                                            llvm::Type *eltTy,
                                            unsigned numElts) const {