Mesa (master): ir_to_mesa: Implement ir_binop_any_nequal using DP4 w/ saturate or DP4 w/SLT

Ian Romanick idr at kemper.freedesktop.org
Tue Aug 16 16:47:54 PDT 2011


Module: Mesa
Branch: master
Commit: e7bf096e8b04931996c8c56548ce0b2c0af3a0dc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e7bf096e8b04931996c8c56548ce0b2c0af3a0dc

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Wed Aug  3 15:35:01 2011 -0700

ir_to_mesa: Implement ir_binop_any_nequal using DP4 w/saturate or DP4 w/SLT

The operation ir_binop_any_nequal is (a.x != b.x) || (a.y != b.y) ||
(a.z != b.z) || (a.w != b.w), and that is the same as any(bvec4(a.x !=
b.x, a.y != b.y, a.z != b.z, a.w != b.w)).  Implement the any() part
the same way the regular ir_unop_any is implemented.

Reviewed-by: Eric Anholt <eric at anholt.net>

---

 src/mesa/program/ir_to_mesa.cpp |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 1bd9a2e..1c674ea 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -1249,8 +1249,26 @@ ir_to_mesa_visitor::visit(ir_expression *ir)
 	  ir->operands[1]->type->is_vector()) {
 	 src_reg temp = get_temp(glsl_type::vec4_type);
 	 emit(ir, OPCODE_SNE, dst_reg(temp), op[0], op[1]);
-	 emit_dp(ir, result_dst, temp, temp, vector_elements);
-	 emit(ir, OPCODE_SNE, result_dst, result_src, src_reg_for_float(0.0));
+
+	 /* After the dot-product, the value will be an integer on the
+	  * range [0,4].  Zero stays zero, and positive values become 1.0.
+	  */
+	 ir_to_mesa_instruction *const dp =
+	    emit_dp(ir, result_dst, temp, temp, vector_elements);
+	 if (this->prog->Target == GL_FRAGMENT_PROGRAM_ARB) {
+	    /* The clamping to [0,1] can be done for free in the fragment
+	     * shader with a saturate.
+	     */
+	    dp->saturate = true;
+	 } else {
+	    /* Negating the result of the dot-product gives values on the range
+	     * [-4, 0].  Zero stays zero, and negative values become 1.0.  This
+	     * achieved using SLT.
+	     */
+	    src_reg slt_src = result_src;
+	    slt_src.negate = ~slt_src.negate;
+	    emit(ir, OPCODE_SLT, result_dst, slt_src, src_reg_for_float(0.0));
+	 }
       } else {
 	 emit(ir, OPCODE_SNE, result_dst, op[0], op[1]);
       }



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