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 <[email protected]>
Reviewed-by: Roland Scheidegger <[email protected]>
Reviewed-by: Brian Paul <[email protected]>

3 files changed, 11 insertions, 16 deletions

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c b/src/gallium/auxiliary/gallivm/lp_bld_tgsi_action.c
index 68bd1243ece..e99c8ef134e 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 bed08522fcd..1f8e62d6f3e 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 13daa62ab62..4d26c465579 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::