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i965/fs: Don't double-accept operands of logical and/or/xor operations. 

If the argument to emit_bool_to_cond_code() is an ir_expression, we
loop over the operands, calling accept() on each of them, which
generates assembly code to compute that subexpression.  We then emit
one or two final instruction that perform the top-level operation on
those operands.

If it's not an expression (say, a boolean-valued variable), we simply
call accept() on the whole value.

In commit 80ecb8f1 (i965/fs: Avoid generating extra AND instructions on
bool logic ops), Eric made logic operations jump out of the expression
path to the non-expression path.

Unfortunately, this meant that we would first accept() the two operands,
skip generating any code that used them, then accept() the whole
expression, generating code for the operands a second time.

Dead code elimination would always remove the first set of redundant
operand assembly, since nothing actually used them.  But we shouldn't
generate it in the first place.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Kenneth Graunke 2013-09-23 13:37:00 -07:00
parent e5c49bc25b
commit aac75f877d
1 changed files with 4 additions and 7 deletions
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11
src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
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@ -1724,7 +1724,10 @@ fs_visitor::emit_bool_to_cond_code(ir_rvalue *ir)
{
ir_expression *expr = ir->as_expression();
if (expr) {
if (expr &&
expr->operation != ir_binop_logic_and &&
expr->operation != ir_binop_logic_or &&
expr->operation != ir_binop_logic_xor) {
fs_reg op[2];
fs_inst *inst;
@ -1744,11 +1747,6 @@ fs_visitor::emit_bool_to_cond_code(ir_rvalue *ir)
inst->conditional_mod = BRW_CONDITIONAL_Z;
break;
case ir_binop_logic_xor:
case ir_binop_logic_or:
case ir_binop_logic_and:
goto out;
case ir_unop_f2b:
if (brw->gen >= 6) {
emit(CMP(reg_null_d, op[0], fs_reg(0.0f), BRW_CONDITIONAL_NZ));
@ -1790,7 +1788,6 @@ fs_visitor::emit_bool_to_cond_code(ir_rvalue *ir)
return;
}
out:
ir->accept(this);
fs_inst *inst = emit(AND(reg_null_d, this->result, fs_reg(1)));