On 08/07/2013 03:45 PM, Ian Romanick wrote:
On 08/05/2013 06:28 PM, Kenneth Graunke wrote:
[snip]
+ * (+f0) IF + * MOV dst src0 + * ELSE + * MOV dst src1 + * ENDIFDo we see many cases of foo = batman; if (condition) foo = robin;
I haven't seen many cases of that, no.
+ * + * which can be easily translated into: + * + * (+f0) SEL dst src0 src1 + * + * If src0 is an immediate value, we promote it to a temporary GRF. + */ +void +fs_visitor::try_replace_with_sel() +{ + fs_inst *endif_inst = (fs_inst *) instructions.get_tail(); + assert(endif_inst->opcode == BRW_OPCODE_ENDIF); + + /* Pattern match in reverse: IF, MOV, ELSE, MOV, ENDIF. */Just curious about the decision to match in reverse...
We do normal code generation for an ir_if, then, after emitting the closing ENDIF, check if it fits the pattern. Since the end of the list is just after the ENDIF, and I don't know how many instructions may have been generated, it makes sense to do it in reverse.
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