Mesa (master): prog_to_nir: Make RSQ properly take the absolute value of its argument.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: 15a12795c6f3edef0e1cbab39b6da3d5b8f64fc3
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=15a12795c6f3edef0e1cbab39b6da3d5b8f64fc3

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Thu Jun  4 01:24:07 2015 -0700

prog_to_nir: Make RSQ properly take the absolute value of its argument.

I just botched this when writing the original code.

>From the ARB_vertex_program specification:
"The RSQ instruction approximates the reciprocal of the square root of
 the absolute value of the scalar operand and replicates it to all four
 components of the result vector."

Fixes a Glean vertProg1 subtest:
RSQ test 2 (reciprocal square root of negative value)

Cc: mesa-stable at lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90547
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Francisco Jerez <currojerez at riseup.net>

---

 src/mesa/program/prog_to_nir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/mesa/program/prog_to_nir.c b/src/mesa/program/prog_to_nir.c
index e986e51..d3e3f15 100644
--- a/src/mesa/program/prog_to_nir.c
+++ b/src/mesa/program/prog_to_nir.c
@@ -764,7 +764,8 @@ ptn_emit_instruction(struct ptn_compile *c, struct prog_instruction *prog_inst)
 
    switch (op) {
    case OPCODE_RSQ:
-      ptn_move_dest(b, dest, nir_frsq(b, ptn_channel(b, src[0], X)));
+      ptn_move_dest(b, dest,
+                    nir_frsq(b, nir_fabs(b, ptn_channel(b, src[0], X))));
       break;
 
    case OPCODE_RCP: