[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291956 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/Target/NVPTX/NVPTXSubtarget.cpp b/lib/Target/NVPTX/NVPTXSubtarget.cpp
index 6e1f427ed02..acbee86ae38 100644
--- a/lib/Target/NVPTX/NVPTXSubtarget.cpp
+++ b/lib/Target/NVPTX/NVPTXSubtarget.cpp
@@ -23,6 +23,11 @@ using namespace llvm;
 #define GET_SUBTARGETINFO_CTOR
 #include "NVPTXGenSubtargetInfo.inc"
 
+static cl::opt<bool>
+    NoF16Math("nvptx-no-f16-math", cl::ZeroOrMore, cl::Hidden,
+              cl::desc("NVPTX Specific: Disable generation of f16 math ops."),
+              cl::init(false));
+
 // Pin the vtable to this file.
 void NVPTXSubtarget::anchor() {}
 
@@ -57,3 +62,7 @@ bool NVPTXSubtarget::hasImageHandles() const {
   // Disabled, otherwise
   return false;
 }
+
+bool NVPTXSubtarget::allowFP16Math() const {
+  return hasFP16Math() && NoF16Math == false;
+}