[OpenCL] Support half precision floating point type literal

[yaxunl]

Summary

OpenCL allows half precision floating point type literals with suffices h or H when cl_khr_fp16 extension is enabled. This change supports that.

Differential Revision: http://reviews.llvm.org/D16865

[pxli168]

lib/Sema/SemaCast.cpp

2397

In the context there is a SrcType you can just use it as you used below.

test/Lexer/opencl-half-literal.cl

6

Did the tests need the constant here?
I think constant is address space in OpenCL, maybe you could remove them.

[yaxunl]

test/Lexer/opencl-half-literal.cl

6

In OpenCL 1.2 and below program scope variable must be in constant address space.
I tried to remove the constant and I got error:
opencl-half-literal.cl Line 5: program scope variable must reside in constant address space

[yaxunl]

Revised as Xiuli Suggested.

[yaxunl]

re-update diff. Accidentally dropped a line in test/SemaOpenCL/half.cl in the last update.

[Anastasia]

I think a reference to Spec section would be nice somewhere either in code or test.

Thanks!

lib/Lex/LiteralSupport.cpp

578

I think the full diff would have been better here. Otherwise, too many fragments without context around makes it hard to review.

test/Lexer/opencl-half-literal.cl

7

That's right, we can only declare program scope variables in a constant AS in OpenCL earlier than v2.0. So it's fine.

[yaxunl]

Add reference to OpenCL extension spec in comments.
Update with full diff.

[pxli168]

LGTM!
Thanks.

[Anastasia]

test/Lexer/opencl-half-literal.cl

11

Could we disable cl_khr_fp16 here and check that we get an error when using half literals.

[yaxunl]

Revised according to Anastasia's comments.

I got difficulty diagnosing half literal as lexical error since the preprocessor and lexer do not know whether OpenCL extension cl_khr_fp16 is enabled or not, so I diagnose half literal used without cl_khr_fp16 enabled as semantic error and added tests to SemaOpenCL.

Also I removed diagnostic for casting from half type since it is unnecessary. If half type value is created when cl_khr_fp16 is not enabled, it will be diagnosed before the cast expression is reached.

[Anastasia]

@pekka, do you have any additional comments here? I believe we are about to complete this work.

Thanks!

lib/Lex/LiteralSupport.cpp

559

. missing

561

. missing

test/SemaOpenCL/half.cl

49

I think you already test this in line 4?

[yaxunl]

test/SemaOpenCL/half.cl

49

I want to check after cl_khr_fp16 is enabled then disabled the behavior is expected. Do you think this is unnecessary?

[yaxunl]

Revised as Anastasia suggested.

Changed comments.
Removed unnecessary tests.

[pekka.jaaskelainen]

Can you add a test that tries to use half precision constants in non OpenCL C mode? Otherwise LGTM.

[yaxunl]

Added a test for half literal in non-OpenCL language as Pekka suggested.

[Anastasia]

LGTM!

[pekka.jaaskelainen]

LGTM!

include/clang/Basic/DiagnosticSemaKinds.td

 def err_opencl_half_load_store : Error<
   "%select{loading directly from|assigning directly to}0 pointer to type %1 is not allowed">;
 def err_opencl_cast_to_half : Error<"casting to type %0 is not allowed">;
+def err_opencl_cast_from_half : Error<"casting from type %0 is not allowed">;
 def err_opencl_half_declaration : Error<
   "declaring variable of type %0 is not allowed">;
 def err_opencl_half_param : Error<

include/clang/Lex/LiteralSupport.h

   bool isUnsigned : 1;
   bool isLong : 1;          // This is *not* set for long long.
   bool isLongLong : 1;
+  bool isHalf : 1;          // 1.0h
   bool isFloat : 1;         // 1.0f
   bool isImaginary : 1;     // 1.0i
   uint8_t MicrosoftInteger; // Microsoft suffix extension i8, i16, i32, or i64.

lib/Lex/LiteralSupport.cpp

   isLong = false;
   isUnsigned = false;
   isLongLong = false;
+  isHalf = false;
   isFloat = false;
   isImaginary = false;
   MicrosoftInteger = 0;

   // we break out of the loop.
   for (; s != ThisTokEnd; ++s) {
     switch (*s) {
+    case 'h':      // FP Suffix for "half"
+    case 'H':
+      if (!PP.getLangOpts().Half) break;
+      if (!isFPConstant) break;  // Error for integer constant.
+      if (isHalf || isFloat || isLong) break; // HH, FH, LH invalid.
+      isHalf = true;
+      continue;  // Success.
     case 'f':      // FP Suffix for "float"
     case 'F':
       if (!isFPConstant) break;  // Error for integer constant.
-      if (isFloat || isLong) break; // FF, LF invalid.
+      if (isHalf || isFloat || isLong) break; // HF, FF, LF invalid.
       isFloat = true;
       continue;  // Success.
     case 'u':

     case 'l':
     case 'L':
       if (isLong || isLongLong) break;  // Cannot be repeated.
-      if (isFloat) break;               // LF invalid.
+      if (isHalf || isFloat) break;     // LH, LF invalid.
 
       // Check for long long.  The L's need to be adjacent and the same case.
       if (s[1] == s[0]) {

       isUnsigned = false;
       isLongLong = false;
       isFloat = false;
+      isHalf = false;
       isImaginary = false;
       MicrosoftInteger = 0;
 

lib/Sema/SemaCast.cpp

       SrcExpr = ExprError();
       return;
     }
+    if (SrcType->isHalfType()) {
+      Self.Diag(SrcExpr.get()->getLocStart(), diag::err_opencl_cast_from_half)
+        << SrcType << SrcExpr.get()->getSourceRange();
+      SrcExpr = ExprError();
+      return;
+    }
   }
 
   // ARC imposes extra restrictions on casts.

lib/Sema/SemaExpr.cpp

 
   if (Literal.isFloatingLiteral()) {
     QualType Ty;
-    if (Literal.isFloat)
+    if (Literal.isHalf)
+      Ty = Context.HalfTy;
+    else if (Literal.isFloat)
       Ty = Context.FloatTy;
     else if (!Literal.isLong)
       Ty = Context.DoubleTy;

test/Lexer/opencl-half-literal.cl

+// RUN: %clang_cc1 %s -fsyntax-only -verify
+
+#pragma OPENCL EXTENSION cl_khr_fp16 : enable
+
+constant half a = 1.0h; 
+constant half aa = 1.0H;
+constant half b = 1.0hh; // expected-error{{invalid suffix 'hh' on floating constant}}
+constant half c = 1.0fh; // expected-error{{invalid suffix 'fh' on floating constant}}
+constant half d = 1.0lh; // expected-error{{invalid suffix 'lh' on floating constant}}
+constant half e = 1.0hf; // expected-error{{invalid suffix 'hf' on floating constant}}

test/SemaOpenCL/half.cl

 
   float c = 1.0f;
   b = (half) c;
+  b = 1.0h;
 
   half *allowed = &p[1];
   half *allowed2 = &*p;