Mesa (master): i965: Always hand the absolute value to RSQ.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: fa0d5a2c5bfb6109d365a6f0b9bee53dfee50325
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=fa0d5a2c5bfb6109d365a6f0b9bee53dfee50325

Author: Eric Anholt <eric at anholt.net>
Date:   Tue Dec  7 12:34:30 2010 -0800

i965: Always hand the absolute value to RSQ.

gen6 builtin RSQ apparently clamps negative values to 0 instead of
returning the RSQ of the absolute value like ARB_fragment_program
desires and pre-gen6 apparently does.

Fixes:
glean/fp1-RSQ test 2 (reciprocal square root of negative value)
glean/vp1-RSQ test 2 (reciprocal square root of negative value)

---

 src/mesa/drivers/dri/i965/brw_vs_emit.c |    2 +-
 src/mesa/drivers/dri/i965/brw_wm_fp.c   |    5 +++++
 2 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vs_emit.c b/src/mesa/drivers/dri/i965/brw_vs_emit.c
index 407358f..1844526 100644
--- a/src/mesa/drivers/dri/i965/brw_vs_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_vs_emit.c
@@ -1958,7 +1958,7 @@ void brw_vs_emit(struct brw_vs_compile *c )
 	 emit_math1(c, BRW_MATH_FUNCTION_INV, dst, args[0], BRW_MATH_PRECISION_FULL);
 	 break;
       case OPCODE_RSQ:
-	 emit_math1(c, BRW_MATH_FUNCTION_RSQ, dst, args[0], BRW_MATH_PRECISION_FULL);
+	 emit_math1(c, BRW_MATH_FUNCTION_RSQ, dst, brw_abs(args[0]), BRW_MATH_PRECISION_FULL);
 	 break;
 
       case OPCODE_SEQ:
diff --git a/src/mesa/drivers/dri/i965/brw_wm_fp.c b/src/mesa/drivers/dri/i965/brw_wm_fp.c
index 36330c1..4759b28 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_fp.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_fp.c
@@ -1131,6 +1131,11 @@ void brw_wm_pass_fp( struct brw_wm_compile *c )
 	 precalc_lit(c, inst);
 	 break;
 
+      case OPCODE_RSQ:
+	 out = emit_scalar_insn(c, inst);
+	 out->SrcReg[0].Abs = GL_TRUE;
+	 break;
+
       case OPCODE_TEX:
 	 precalc_tex(c, inst);
 	 break;