Add the intrinsic __builtin_convertvector

LLVM supports applying conversion instructions to vectors of the same number of
elements (fptrunc, fptosi, etc.) but there had been no way for a Clang user to
cause such instructions to be generated when using builtin vector types.

C-style casting on vectors is already defined in terms of bitcasts, and so
cannot be used for these conversions as well (without leading to a very
confusing set of semantics). As a result, this adds a __builtin_convertvector
intrinsic (patterned after the OpenCL __builtin_astype intrinsic). This is
intended to aid the creation of vector intrinsic headers that create generic IR
instead of target-dependent intrinsics (in other words, this is a generic
_mm_cvtepi32_ps). As noted in the documentation, the action of
__builtin_convertvector is defined in terms of the action of a C-style cast on
each vector element.

llvm-svn: 190915

1 files changed, 29 insertions, 0 deletions

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 07d8ba5a904..bbc7dadde8f 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -888,6 +888,7 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
   case tok::kw___builtin_offsetof:
   case tok::kw___builtin_choose_expr:
   case tok::kw___builtin_astype: // primary-expression: [OCL] as_type()
+  case tok::kw___builtin_convertvector:
     return ParseBuiltinPrimaryExpression();
   case tok::kw___null:
     return Actions.ActOnGNUNullExpr(ConsumeToken());
@@ -1918,6 +1919,34 @@ ExprResult Parser::ParseBuiltinPrimaryExpression() {
                                   ConsumeParen());
     break;
   }
+  case tok::kw___builtin_convertvector: {
+    // The first argument is an expression to be converted, followed by a comma.
+    ExprResult Expr(ParseAssignmentExpression());
+    if (Expr.isInvalid()) {
+      SkipUntil(tok::r_paren);
+      return ExprError();
+    }
+    
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "", 
+                         tok::r_paren))
+      return ExprError();
+    
+    // Second argument is the type to bitcast to.
+    TypeResult DestTy = ParseTypeName();
+    if (DestTy.isInvalid())
+      return ExprError();
+    
+    // Attempt to consume the r-paren.
+    if (Tok.isNot(tok::r_paren)) {
+      Diag(Tok, diag::err_expected_rparen);
+      SkipUntil(tok::r_paren);
+      return ExprError();
+    }
+    
+    Res = Actions.ActOnConvertVectorExpr(Expr.take(), DestTy.get(), StartLoc, 
+                                         ConsumeParen());
+    break;
+  }
   }
 
   if (Res.isInvalid())