Extend vector member references to include {.hi, .lo, .e, .o} which return a

vector of the same element type and half the width, with the high, low, even,
and odd elements respectively.

Allow member references to member references, so that .hi.hi gives you the high
quarter of a vector.  This is fairly convenient syntax for some insert/extract
operations.

Remove some unnecessary methods/types in the ExtVectorElementExpr class.

llvm-svn: 50892

1 files changed, 28 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4dcc6843184..5341ee7faa3 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -431,7 +431,8 @@ ActOnArraySubscriptExpr(ExprTy *Base, SourceLocation LLoc,
     IndexExpr = RHSExp;
     
     // Component access limited to variables (reject vec4.rg[1]).
-    if (!isa<DeclRefExpr>(BaseExpr) && !isa<ArraySubscriptExpr>(BaseExpr)) 
+    if (!isa<DeclRefExpr>(BaseExpr) && !isa<ArraySubscriptExpr>(BaseExpr) &&
+        !isa<ExtVectorElementExpr>(BaseExpr))
       return Diag(LLoc, diag::err_ext_vector_component_access, 
                   SourceRange(LLoc, RLoc));
     // FIXME: need to deal with const...
@@ -461,6 +462,10 @@ QualType Sema::
 CheckExtVectorComponent(QualType baseType, SourceLocation OpLoc,
                         IdentifierInfo &CompName, SourceLocation CompLoc) {
   const ExtVectorType *vecType = baseType->getAsExtVectorType();
+
+  // This flag determines whether or not the component is to be treated as a 
+  // special name, or a regular GLSL-style component access.
+  bool SpecialComponent = false;
   
   // The vector accessor can't exceed the number of elements.
   const char *compStr = CompName.getName();
@@ -469,8 +474,13 @@ CheckExtVectorComponent(QualType baseType, SourceLocation OpLoc,
                 baseType.getAsString(), SourceRange(CompLoc));
     return QualType();
   }
-  // The component names must come from the same set.
-  if (vecType->getPointAccessorIdx(*compStr) != -1) {
+
+  // Check that we've found one of the special components, or that the component
+  // names must come from the same set.
+  if (!strcmp(compStr, "hi") || !strcmp(compStr, "lo") || 
+      !strcmp(compStr, "e") || !strcmp(compStr, "o")) {
+    SpecialComponent = true;
+  } else if (vecType->getPointAccessorIdx(*compStr) != -1) {
     do
       compStr++;
     while (*compStr && vecType->getPointAccessorIdx(*compStr) != -1);
@@ -484,7 +494,7 @@ CheckExtVectorComponent(QualType baseType, SourceLocation OpLoc,
     while (*compStr && vecType->getTextureAccessorIdx(*compStr) != -1);
   }
     
-  if (*compStr) { 
+  if (!SpecialComponent && *compStr) { 
     // We didn't get to the end of the string. This means the component names
     // didn't come from the same set *or* we encountered an illegal name.
     Diag(OpLoc, diag::err_ext_vector_component_name_illegal, 
@@ -499,17 +509,27 @@ CheckExtVectorComponent(QualType baseType, SourceLocation OpLoc,
     else
       break;
   }
-  if (*compStr) { 
+  if (!SpecialComponent && *compStr) { 
     // We didn't get to the end of the string. This means a component accessor
     // exceeds the number of elements in the vector.
     Diag(OpLoc, diag::err_ext_vector_component_exceeds_length, 
                 baseType.getAsString(), SourceRange(CompLoc));
     return QualType();
   }
+
+  // If we have a special component name, verify that the current vector length
+  // is an even number, since all special component names return exactly half
+  // the elements.
+  if (SpecialComponent && (vecType->getNumElements() & 1U)) {
+    return QualType();
+  }
+  
   // The component accessor looks fine - now we need to compute the actual type.
   // The vector type is implied by the component accessor. For example, 
   // vec4.b is a float, vec4.xy is a vec2, vec4.rgb is a vec3, etc.
-  unsigned CompSize = strlen(CompName.getName());
+  // vec4.hi, vec4.lo, vec4.e, and vec4.o all return vec2.
+  unsigned CompSize = SpecialComponent ? vecType->getNumElements() / 2
+                                       : strlen(CompName.getName());
   if (CompSize == 1)
     return vecType->getElementType();
     
@@ -566,7 +586,8 @@ ActOnMemberReferenceExpr(ExprTy *Base, SourceLocation OpLoc,
                           MemberLoc, MemberType);
   } else if (BaseType->isExtVectorType() && OpKind == tok::period) {
     // Component access limited to variables (reject vec4.rg.g).
-    if (!isa<DeclRefExpr>(BaseExpr) && !isa<ArraySubscriptExpr>(BaseExpr))
+    if (!isa<DeclRefExpr>(BaseExpr) && !isa<ArraySubscriptExpr>(BaseExpr) &&
+        !isa<ExtVectorElementExpr>(BaseExpr))
       return Diag(OpLoc, diag::err_ext_vector_component_access, 
                   SourceRange(MemberLoc));
     QualType ret = CheckExtVectorComponent(BaseType, OpLoc, Member, MemberLoc);