[NVPTX] Added support for half-precision floating point.

Only scalar half-precision operations are supported at the moment.

- Adds general support for 'half' type in NVPTX.
- fp16 math operations are supported on sm_53+ GPUs only
  (can be disabled with --nvptx-no-f16-math).
- Type conversions to/from fp16 are supported on all GPU variants.
- On GPU variants that do not have full fp16 support (or if it's disabled),
  fp16 operations are promoted to fp32 and results are converted back
  to fp16 for storage.

Differential Revision: https://reviews.llvm.org/D28540

llvm-svn: 291956

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/Target/NVPTX/NVPTXMCExpr.h b/llvm/lib/Target/NVPTX/NVPTXMCExpr.h
index 7f833c42fa8..95741d9b045 100644
--- a/llvm/lib/Target/NVPTX/NVPTXMCExpr.h
+++ b/llvm/lib/Target/NVPTX/NVPTXMCExpr.h
@@ -22,8 +22,9 @@ class NVPTXFloatMCExpr : public MCTargetExpr {
 public:
   enum VariantKind {
     VK_NVPTX_None,
-    VK_NVPTX_SINGLE_PREC_FLOAT,   // FP constant in single-precision
-    VK_NVPTX_DOUBLE_PREC_FLOAT    // FP constant in double-precision
+    VK_NVPTX_HALF_PREC_FLOAT,   // FP constant in half-precision
+    VK_NVPTX_SINGLE_PREC_FLOAT, // FP constant in single-precision
+    VK_NVPTX_DOUBLE_PREC_FLOAT  // FP constant in double-precision
   };
 
 private:
@@ -40,6 +41,11 @@ public:
   static const NVPTXFloatMCExpr *create(VariantKind Kind, const APFloat &Flt,
                                         MCContext &Ctx);
 
+  static const NVPTXFloatMCExpr *createConstantFPHalf(const APFloat &Flt,
+                                                        MCContext &Ctx) {
+    return create(VK_NVPTX_HALF_PREC_FLOAT, Flt, Ctx);
+  }
+
   static const NVPTXFloatMCExpr *createConstantFPSingle(const APFloat &Flt,
                                                         MCContext &Ctx) {
     return create(VK_NVPTX_SINGLE_PREC_FLOAT, Flt, Ctx);