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authorBrian Paul <brianp@vmware.com>2009-09-29 18:57:13 -0600
committerBrian Paul <brianp@vmware.com>2009-09-29 18:57:13 -0600
commit65765c9f2c5d3568608bde57db0bf44d6b724755 (patch)
tree9825cbfd5c239e2bef19d1ea40b1fc1cb743592c /src/mesa
parent3c794e45b02c66ce3f52fe359f733e4d7d2ce315 (diff)
glsl: rewrite sqrt(x) intrinsic to handle x=0
Since sqrt() is basically implemented in terms of RSQ/RCP we'll do a divide by zero if x=0 and wind up with unpredictable results. Now use CMP instruction to test for x<=0 and return zero in that case.
Diffstat (limited to 'src/mesa')
-rw-r--r--src/mesa/shader/slang/library/slang_common_builtin.gc76
1 files changed, 42 insertions, 34 deletions
diff --git a/src/mesa/shader/slang/library/slang_common_builtin.gc b/src/mesa/shader/slang/library/slang_common_builtin.gc
index 9764fc25b0..56de47ee8d 100644
--- a/src/mesa/shader/slang/library/slang_common_builtin.gc
+++ b/src/mesa/shader/slang/library/slang_common_builtin.gc
@@ -602,42 +602,50 @@ vec4 exp2(const vec4 a)
float sqrt(const float x)
{
+ const float nx = -x;
float r;
__asm float_rsq r, x;
- __asm float_rcp __retVal, r;
-}
-
-vec2 sqrt(const vec2 v)
-{
- float r;
- __asm float_rsq r, v.x;
- __asm float_rcp __retVal.x, r;
- __asm float_rsq r, v.y;
- __asm float_rcp __retVal.y, r;
-}
-
-vec3 sqrt(const vec3 v)
-{
- float r;
- __asm float_rsq r, v.x;
- __asm float_rcp __retVal.x, r;
- __asm float_rsq r, v.y;
- __asm float_rcp __retVal.y, r;
- __asm float_rsq r, v.z;
- __asm float_rcp __retVal.z, r;
-}
-
-vec4 sqrt(const vec4 v)
-{
- float r;
- __asm float_rsq r, v.x;
- __asm float_rcp __retVal.x, r;
- __asm float_rsq r, v.y;
- __asm float_rcp __retVal.y, r;
- __asm float_rsq r, v.z;
- __asm float_rcp __retVal.z, r;
- __asm float_rsq r, v.w;
- __asm float_rcp __retVal.w, r;
+ __asm float_rcp r, r;
+ __asm vec4_cmp __retVal, nx, r, 0.0;
+}
+
+vec2 sqrt(const vec2 x)
+{
+ const vec2 nx = -x, zero = vec2(0.0);
+ vec2 r;
+ __asm float_rsq r.x, x.x;
+ __asm float_rsq r.y, x.y;
+ __asm float_rcp r.x, r.x;
+ __asm float_rcp r.y, r.y;
+ __asm vec4_cmp __retVal, nx, r, zero;
+}
+
+vec3 sqrt(const vec3 x)
+{
+ const vec3 nx = -x, zero = vec3(0.0);
+ vec3 r;
+ __asm float_rsq r.x, x.x;
+ __asm float_rsq r.y, x.y;
+ __asm float_rsq r.z, x.z;
+ __asm float_rcp r.x, r.x;
+ __asm float_rcp r.y, r.y;
+ __asm float_rcp r.z, r.z;
+ __asm vec4_cmp __retVal, nx, r, zero;
+}
+
+vec4 sqrt(const vec4 x)
+{
+ const vec4 nx = -x, zero = vec4(0.0);
+ vec4 r;
+ __asm float_rsq r.x, x.x;
+ __asm float_rsq r.y, x.y;
+ __asm float_rsq r.z, x.z;
+ __asm float_rsq r.w, x.w;
+ __asm float_rcp r.x, r.x;
+ __asm float_rcp r.y, r.y;
+ __asm float_rcp r.z, r.z;
+ __asm float_rcp r.w, r.w;
+ __asm vec4_cmp __retVal, nx, r, zero;
}