From: Ian Romanick <ian.d.roman...@intel.com>
ir_rvalue_visitor visits each rvalue on exit. When visiting a large
expression, the leaf expressions will be visited and eliminated first.
Once one leaf expression was replaced, it would no longer match a
potentially much larger tree. This means that code like:
x = a + (b * c);
y = -(a + (b * c));
would effectively be replaced by
tmp = b * c;
x = a + tmp;
y = -(a + tmp);
As a result both opportunities for generating a MAD would be lost, and
we would generate worse code.
Using ir_rvalue_enter_visitor means that larger expression trees will be
checked first, and we have the potential to eliminate much larger
expressions.
I believe that opt_cse.cpp predates the existence of
ir_rvalue_enter_visitor.
Shader-db results:
GM45:
total instructions in shared programs: 4063165 -> 4061744 (-0.03%)
instructions in affected programs: 21664 -> 20243 (-6.56%)
helped: 259
GM45 NIR:
total instructions in shared programs: 4082044 -> 4080646 (-0.03%)
instructions in affected programs: 21091 -> 19693 (-6.63%)
helped: 255
HURT: 1
Iron Lake:
total instructions in shared programs: 5480334 -> 5478897 (-0.03%)
instructions in affected programs: 25798 -> 24361 (-5.57%)
helped: 273
HURT: 1
Iron Lake NIR:
total instructions in shared programs: 5678776 -> 5677395 (-0.02%)
instructions in affected programs: 21744 -> 20363 (-6.35%)
helped: 263
HURT: 2
Sandy Bridge:
total instructions in shared programs: 7318903 -> 7316983 (-0.03%)
instructions in affected programs: 37937 -> 36017 (-5.06%)
helped: 398
HURT: 26
Sandy Bridge NIR:
total instructions in shared programs: 7329995 -> 7328069 (-0.03%)
instructions in affected programs: 32487 -> 30561 (-5.93%)
helped: 384
HURT: 6
Ivy Bridge:
total instructions in shared programs: 6766579 -> 6765409 (-0.02%)
instructions in affected programs: 18110 -> 16940 (-6.46%)
helped: 288
HURT: 16
GAINED: 1
Ivy Bridge NIR:
total instructions in shared programs: 6769314 -> 6768159 (-0.02%)
instructions in affected programs: 11063 -> 9908 (-10.44%)
helped: 264
HURT: 6
Haswell:
total instructions in shared programs: 6226294 -> 6225102 (-0.02%)
instructions in affected programs: 17555 -> 16363 (-6.79%)
helped: 297
HURT: 10
GAINED: 1
Haswell NIR:
total instructions in shared programs: 6183693 -> 6182538 (-0.02%)
instructions in affected programs: 10990 -> 9835 (-10.51%)
helped: 264
HURT: 6
Broadwell:
total instructions in shared programs: 7285895 -> 7284537 (-0.02%)
instructions in affected programs: 31977 -> 30619 (-4.25%)
helped: 357
HURT: 6
Broadwell NIR:
total instructions in shared programs: 7501711 -> 7501544 (-0.00%)
instructions in affected programs: 7174 -> 7007 (-2.33%)
helped: 87
HURT: 2
Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
---
src/glsl/opt_cse.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/glsl/opt_cse.cpp b/src/glsl/opt_cse.cpp
index 4b8e9a0..425eebc 100644
--- a/src/glsl/opt_cse.cpp
+++ b/src/glsl/opt_cse.cpp
@@ -99,7 +99,7 @@ public:
ir_variable *var;
};
-class cse_visitor : public ir_rvalue_visitor {
+class cse_visitor : public ir_rvalue_enter_visitor {
public:
cse_visitor(exec_list *validate_instructions)
: validate_instructions(validate_instructions)
--
2.1.0
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