glsl: Add ir_binop_vector_extract

The new opcode is used to get a single field from a vector.  The field
index may not be constant.  This will eventually replace
ir_dereference_array of vectors.  This is similar to the extractelement
instruction in LLVM IR.

http://llvm.org/docs/LangRef.html#extractelement-instruction

v2: Convert tabs to spaces.  Suggested by Eric.

v3: Add array index range checking to ir_binop_vector_extract constant
expression handling.  Suggested by Ken.

v4: Use CLAMP instead of MIN2(MAX2()).  Suggested by Ken.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/ir.cpp

@@ -399,6 +399,10 @@ ir_expression::ir_expression(int op, ir_rvalue *op0, ir_rvalue *op1)
       this->type = op0->type;
       break;
 
+   case ir_binop_vector_extract:
+      this->type = op0->type->get_scalar_type();
+      break;
+
    default:
       assert(!"not reached: missing automatic type setup for ir_expression");
       this->type = glsl_type::float_type;
@@ -510,6 +514,7 @@ static const char *const operator_strs[] = {
    "packHalf2x16_split",
    "bfm",
    "ubo_load",
+   "vector_extract",
    "lrp",
    "bfi",
    "bitfield_extract",