Mesa (master): vc4: Optimize SF(ITOF(x)) -> SF(x).

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 5a1352289862a9bd695a15009c69cad54727c66b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=5a1352289862a9bd695a15009c69cad54727c66b

Author: Eric Anholt <eric at anholt.net>
Date:   Thu Oct  9 09:36:03 2014 +0200

vc4: Optimize SF(ITOF(x)) -> SF(x).

This is a common production of st_glsl_to_tgsi, because CMP takes a float
argument.

---

 src/gallium/drivers/vc4/vc4_opt_algebraic.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/gallium/drivers/vc4/vc4_opt_algebraic.c b/src/gallium/drivers/vc4/vc4_opt_algebraic.c
index 4155e72..e247f30 100644
--- a/src/gallium/drivers/vc4/vc4_opt_algebraic.c
+++ b/src/gallium/drivers/vc4/vc4_opt_algebraic.c
@@ -91,6 +91,22 @@ qir_opt_algebraic(struct vc4_compile *c)
                         defs[inst->dst.index] = inst;
 
                 switch (inst->op) {
+                case QOP_SF:
+                        /* SF just looks at the sign bit, or whether all the
+                         * bits are 0.  This is preserved across an itof
+                         * transformation.
+                         */
+                        if (inst->src[0].file == QFILE_TEMP &&
+                            defs[inst->src[0].index]->op == QOP_ITOF) {
+                                dump_from(c, inst);
+                                inst->src[0] =
+                                        defs[inst->src[0].index]->src[0];
+                                progress =  true;
+                                dump_to(c, inst);
+                                break;
+                        }
+                        break;
+
                 case QOP_SEL_X_Y_ZS:
                 case QOP_SEL_X_Y_ZC:
                 case QOP_SEL_X_Y_NS: