Bug #:

Submitted by:
Reviewed by:
Two vector fixes:

- Sema::CheckAssignmentConstraints() needs to compare the canonical type.
- Expr::isLvalue() needs to disallow subscripting into a vector returned by a function. This
follows the rules for struct returns (in C, at least...C++ is another story:-)

Here is an example...

float4 float4_return()
{
    float4 xx;

    return xx;
}
void add_float4_void_return(float4 *a, float4 *b, float4 *result)
{
    float f;
    float4_return()[1] = f; // now illegal
}

llvm-svn: 39728