[Mesa-dev] [PATCH] i965: Fix if-statements with boolean comparisons on Sandybridge.

[Kenneth Graunke]

In the past, we stored booleans as integer 0 or 1.  At some point, we
changed to storing them as 0 or some non-zero value.  The Sandybridge
specific code for emitting IF instructions with embedded conditional
modifiers was not updated to account for this change.

For code such as

   if (bool_a == bool_b)

we cannot simply emit an equality comparison: even if both operands are
true, they may be represented by two different non-zero values.  We must
first normalize them to 0 or 1 so that they can be compared properly.

Fixes piglit test spec/glsl-1.10/execution/fs-bool-less-compare-true.
Fixes at least 9 subcases of oglconform's shad-compiler test:
- TestLessThanEquali
- TestGreaterThan
- TestGreaterThani
- TestGreaterThanEqual
- TestGreaterThanEquali
- TestEqualb
- TestNotEqual
- TestNotEquali
- TestNotEqualb

NOTE: This is a candidate for the 9.0 branch (but not 8.0).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54709
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=48629
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index d3cbde3..320e2f0 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -1650,6 +1650,9 @@ fs_visitor::emit_if_gen6(ir_if *ir)
       case ir_binop_all_equal:
       case ir_binop_nequal:
       case ir_binop_any_nequal:
+	 resolve_bool_comparison(expr->operands[0], &op[0]);
+	 resolve_bool_comparison(expr->operands[1], &op[1]);
+
 	 inst = emit(BRW_OPCODE_IF, reg_null_d, op[0], op[1]);
 	 inst->conditional_mod =
 	    brw_conditional_for_comparison(expr->operation);
-- 
1.7.11.4