Mesa (master): gallium: fixup definitions of the rsq and sqrt

[Zack Rusin]

Module: Mesa
Branch: master
Commit: 00cd455bd50c6b16b2f72a6d2726de3d3818c7f5
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=00cd455bd50c6b16b2f72a6d2726de3d3818c7f5

Author: Zack Rusin <zackr at vmware.com>
Date:   Thu Jul 11 12:16:06 2013 -0400

gallium: fixup definitions of the rsq and sqrt

GLSL spec says that rsq is undefined for src<=0, but the D3D10
spec says it needs to be a NaN, so lets stop taking an absolute
value of the source which completely breaks that behavior. For
the gl program we can simply insert an extra abs instrunction
which produces the desired behavior there.

Signed-off-by: Zack Rusin <zackr at vmware.com>
Reviewed-by: Roland Scheidegger <sroland at vmware.com>
Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c |    5 -----
 src/gallium/auxiliary/tgsi/tgsi_exec.c             |   16 ++++++++--------
 src/gallium/docs/source/tgsi.rst                   |    6 +++---
 src/mesa/state_tracker/st_mesa_to_tgsi.c           |    6 ++++--
 4 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
index 68bd124..e99c8ef 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
@@ -633,8 +633,6 @@ rsq_emit(
    struct lp_build_tgsi_context * bld_base,
    struct lp_build_emit_data * emit_data)
 {
-   emit_data->args[0] = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_ABS,
-                                               emit_data->args[0]);
    if (bld_base->rsq_action.emit) {
       bld_base->rsq_action.emit(&bld_base->rsq_action, bld_base, emit_data);
    } else {
@@ -1349,9 +1347,6 @@ rcp_emit_cpu(
 }
 
 /* Reciprical squareroot (CPU Only) */
-
-/* This is not the same as TGSI_OPCODE_RSQ, which requres the argument to be
- * greater than or equal to 0 */
 static void
 recip_sqrt_emit_cpu(
    const struct lp_build_tgsi_action * action,
diff --git a/src/gallium/auxiliary/tgsi/tgsi_exec.c b/src/gallium/auxiliary/tgsi/tgsi_exec.c
index bed0852..1f8e62d 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_exec.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_exec.c
@@ -339,20 +339,20 @@ micro_rsq(union tgsi_exec_channel *dst,
    assert(src->f[2] != 0.0f);
    assert(src->f[3] != 0.0f);
 #endif
-   dst->f[0] = 1.0f / sqrtf(fabsf(src->f[0]));
-   dst->f[1] = 1.0f / sqrtf(fabsf(src->f[1]));
-   dst->f[2] = 1.0f / sqrtf(fabsf(src->f[2]));
-   dst->f[3] = 1.0f / sqrtf(fabsf(src->f[3]));
+   dst->f[0] = 1.0f / sqrtf(src->f[0]);
+   dst->f[1] = 1.0f / sqrtf(src->f[1]);
+   dst->f[2] = 1.0f / sqrtf(src->f[2]);
+   dst->f[3] = 1.0f / sqrtf(src->f[3]);
 }
 
 static void
 micro_sqrt(union tgsi_exec_channel *dst,
            const union tgsi_exec_channel *src)
 {
-   dst->f[0] = sqrtf(fabsf(src->f[0]));
-   dst->f[1] = sqrtf(fabsf(src->f[1]));
-   dst->f[2] = sqrtf(fabsf(src->f[2]));
-   dst->f[3] = sqrtf(fabsf(src->f[3]));
+   dst->f[0] = sqrtf(src->f[0]);
+   dst->f[1] = sqrtf(src->f[1]);
+   dst->f[2] = sqrtf(src->f[2]);
+   dst->f[3] = sqrtf(src->f[3]);
 }
 
 static void
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 13daa62..4d26c46 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -94,16 +94,16 @@ This instruction replicates its result.
 
 .. opcode:: RSQ - Reciprocal Square Root
 
-This instruction replicates its result.
+This instruction replicates its result. The results are undefined for src <= 0.
 
 .. math::
 
-  dst = \frac{1}{\sqrt{|src.x|}}
+  dst = \frac{1}{\sqrt{src.x}}
 
 
 .. opcode:: SQRT - Square Root
 
-This instruction replicates its result.
+This instruction replicates its result. The results are undefined for src < 0.
 
 .. math::
 
diff --git a/src/mesa/state_tracker/st_mesa_to_tgsi.c b/src/mesa/state_tracker/st_mesa_to_tgsi.c
index 7f30697..67c6f53 100644
--- a/src/mesa/state_tracker/st_mesa_to_tgsi.c
+++ b/src/mesa/state_tracker/st_mesa_to_tgsi.c
@@ -615,8 +615,6 @@ translate_opcode( unsigned op )
       return TGSI_OPCODE_RCP;
    case OPCODE_RET:
       return TGSI_OPCODE_RET;
-   case OPCODE_RSQ:
-      return TGSI_OPCODE_RSQ;
    case OPCODE_SCS:
       return TGSI_OPCODE_SCS;
    case OPCODE_SEQ:
@@ -756,6 +754,10 @@ compile_instruction(
       emit_ddy( t, dst[0], &inst->SrcReg[0] );
       break;
 
+   case OPCODE_RSQ:
+      ureg_RSQ( ureg, dst[0], ureg_abs(src[0]) );
+      break;
+
    default:
       ureg_insn( ureg, 
                  translate_opcode( inst->Opcode ),