[Mesa-dev] [PATCH] R600/SI: Fix fneg for 0.0

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

V_ADD_F32 with source modifier does not produce -0.0 for this. Just
manipulate the sign bit directly instead.

Also add a pattern for (fneg (fabs ...)).

Fixes a bunch of bit encoding piglit tests with radeonsi.

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 lib/Target/R600/SIInstructions.td | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/lib/Target/R600/SIInstructions.td b/lib/Target/R600/SIInstructions.td
index 912b59a..43fe63c 100644
--- a/lib/Target/R600/SIInstructions.td
+++ b/lib/Target/R600/SIInstructions.td
@@ -1684,15 +1684,18 @@ def : Pat <
 >;
 
 def : Pat <
+  (fneg (fabs f32:$src)),
+  (V_OR_B32_e32 $src, (V_MOV_B32_e32 0x80000000)) /* Set sign bit */
+>;
+
+def : Pat <
   (fabs f32:$src),
-  (V_ADD_F32_e64 $src, (i32 0 /* SRC1 */),
-   1 /* ABS */, 0 /* CLAMP */, 0 /* OMOD */, 0 /* NEG */)
+  (V_AND_B32_e32 $src, (V_MOV_B32_e32 0x7fffffff)) /* Clear sign bit */
 >;
 
 def : Pat <
   (fneg f32:$src),
-  (V_ADD_F32_e64 $src, (i32 0 /* SRC1 */),
-   0 /* ABS */, 0 /* CLAMP */, 0 /* OMOD */, 1 /* NEG */)
+  (V_XOR_B32_e32 $src, (V_MOV_B32_e32 0x80000000)) /* Toggle sign bit */
 >;
 
 /********** ================== **********/
-- 
1.8.5.3