The next patch adds an algebraic optimization for the pattern
sqrt a, b
rcp c, a
and turns it into
sqrt a, b
rsq c, b
but many vertex shaders do
a = sqrt(b);
var1 /= a;
var2 /= a;
which generates
sqrt a, b
rcp c, a
rcp d, a
If we apply the algebraic optimization before CSE, we'll end up with
sqrt a, b
rsq c, b
rcp d, a
Applying CSE combines the RCP instructions, preventing this from
happening.
No shader-db changes.
---
src/mesa/drivers/dri/i965/brw_vec4.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp
b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 022ed37..e0a3d5f 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1790,8 +1790,8 @@ vec4_visitor::run()
OPT(dead_code_eliminate);
OPT(dead_control_flow_eliminate, this);
OPT(opt_copy_propagation);
- OPT(opt_algebraic);
OPT(opt_cse);
+ OPT(opt_algebraic);
OPT(opt_register_coalesce);
} while (progress);
--
1.8.5.5
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