[PATCH] D42318: [ARM] Pass _Float16 as int or float

[Sjoerd Meijer via Phabricator via cfe-commits]

SjoerdMeijer created this revision.
SjoerdMeijer added reviewers: olista01, t.p.northover, rjmccall, aschwaighofer.
Herald added subscribers: kristof.beyls, javed.absar, aemerson.

Pass and return _Float16 as if it were an int or float for ARM, but with the
top 16 bits unspecified, similarly like we already do for __fp16.

      

We will implement proper half-precision function argument lowering in the ARM backend
soon, but want to use this workaround in the mean time.


https://reviews.llvm.org/D42318

Files:
  include/clang/AST/Type.h
  lib/CodeGen/TargetInfo.cpp
  test/CodeGen/arm-float16-arguments.c


Index: test/CodeGen/arm-float16-arguments.c
===================================================================
--- /dev/null
+++ test/CodeGen/arm-float16-arguments.c
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -triple armv7a--none-eabi -target-abi aapcs -mfloat-abi soft -fallow-half-arguments-and-returns -emit-llvm -o - -O1 %s | FileCheck %s --check-prefix=CHECK --check-prefix=SOFT
+// RUN: %clang_cc1 -triple armv7a--none-eabi -target-abi aapcs -mfloat-abi hard -fallow-half-arguments-and-returns -emit-llvm -o - -O1 %s | FileCheck %s --check-prefix=CHECK --check-prefix=HARD
+// RUN: %clang_cc1 -triple armv7a--none-eabi -target-abi aapcs -mfloat-abi soft -fnative-half-arguments-and-returns -emit-llvm -o - -O1 %s | FileCheck %s --check-prefix=NATIVE
+
+_Float16 g;
+
+void t1(_Float16 a) { g = a; }
+// SOFT: define void @t1(i32 [[PARAM:%.*]])
+// SOFT: [[TRUNC:%.*]] = trunc i32 [[PARAM]] to i16
+// HARD: define arm_aapcs_vfpcc void @t1(float [[PARAM:%.*]])
+// HARD: [[BITCAST:%.*]] = bitcast float [[PARAM]] to i32
+// HARD: [[TRUNC:%.*]] = trunc i32 [[BITCAST]] to i16
+// CHECK: store i16 [[TRUNC]], i16* bitcast (half* @g to i16*)
+// NATIVE: define void @t1(half [[PARAM:%.*]])
+// NATIVE: store half [[PARAM]], half* @g
+
+_Float16 t2() { return g; }
+// SOFT: define i32 @t2()
+// HARD: define arm_aapcs_vfpcc float @t2()
+// NATIVE: define half @t2()
+// CHECK: [[LOAD:%.*]] = load i16, i16* bitcast (half* @g to i16*)
+// CHECK: [[ZEXT:%.*]] = zext i16 [[LOAD]] to i32
+// SOFT: ret i32 [[ZEXT]]
+// HARD: [[BITCAST:%.*]] = bitcast i32 [[ZEXT]] to float
+// HARD: ret float [[BITCAST]]
+// NATIVE: [[LOAD:%.*]] = load half, half* @g
+// NATIVE: ret half [[LOAD]]
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -5721,10 +5721,11 @@
     return getNaturalAlignIndirect(Ty, /*ByVal=*/false);
   }
 
-  // __fp16 gets passed as if it were an int or float, but with the top 16 bits
-  // unspecified. This is not done for OpenCL as it handles the half type
-  // natively, and does not need to interwork with AAPCS code.
-  if (Ty->isHalfType() && !getContext().getLangOpts().NativeHalfArgsAndReturns) {
+  // _Float16 and __fp16 get passed as if it were an int or float, but with
+  // the top 16 bits unspecified. This is not done for OpenCL as it handles the
+  // half type natively, and does not need to interwork with AAPCS code.
+  if ((Ty->isFloat16Type() || Ty->isHalfType()) &&
+      !getContext().getLangOpts().NativeHalfArgsAndReturns) {
     llvm::Type *ResType = IsEffectivelyAAPCS_VFP ?
       llvm::Type::getFloatTy(getVMContext()) :
       llvm::Type::getInt32Ty(getVMContext());
@@ -5919,10 +5920,11 @@
     return getNaturalAlignIndirect(RetTy);
   }
 
-  // __fp16 gets returned as if it were an int or float, but with the top 16
-  // bits unspecified. This is not done for OpenCL as it handles the half type
-  // natively, and does not need to interwork with AAPCS code.
-  if (RetTy->isHalfType() && !getContext().getLangOpts().NativeHalfArgsAndReturns) {
+  // _Float16 and __fp16 get returned as if it were an int or float, but with
+  // the top 16 bits unspecified. This is not done for OpenCL as it handles the
+  // half type natively, and does not need to interwork with AAPCS code.
+  if ((RetTy->isFloat16Type() || RetTy->isHalfType()) &&
+      !getContext().getLangOpts().NativeHalfArgsAndReturns) {
     llvm::Type *ResType = IsEffectivelyAAPCS_VFP ?
       llvm::Type::getFloatTy(getVMContext()) :
       llvm::Type::getInt32Ty(getVMContext());
Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -1728,6 +1728,7 @@
   bool isAnyComplexType() const;   // C99 6.2.5p11 (complex) + Complex Int.
   bool isFloatingType() const;     // C99 6.2.5p11 (real floating + complex)
   bool isHalfType() const;         // OpenCL 6.1.1.1, NEON (IEEE 754-2008 half)
+  bool isFloat16Type() const;      // C11 extension ISO/IEC TS 18661
   bool isRealType() const;         // C99 6.2.5p17 (real floating + integer)
   bool isArithmeticType() const;   // C99 6.2.5p18 (integer + floating)
   bool isVoidType() const;         // C99 6.2.5p19
@@ -6179,6 +6180,12 @@
   return false;
 }
 
+inline bool Type::isFloat16Type() const {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
+    return BT->getKind() == BuiltinType::Float16;
+  return false;
+}
+
 inline bool Type::isNullPtrType() const {
   if (const BuiltinType *BT = getAs<BuiltinType>())
     return BT->getKind() == BuiltinType::NullPtr;


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