Hi, with the changes in the IVopts pass from last year I see a reduced number of induction variables used for the first of the 3 hotloops in the 436.cactus benchmark:
http://gcc.gnu.org/viewcvs?view=revision&revision=162653 Which leads to an heavily increased number of instructions in the body of the first loop in the resulting binary: with GCC 4.5: BB 4: 52 <- number of instructions with GCC 4.6: BB 4: 110 <- similiar result with GCC head With GCC 4.6 a lot of loop invariant integer arithmetic is done in order to calculate the addresses which are used to access the array fields. Adding another invariant motion pass improves the loop even beyond the 4.5 result: with GCC 4.6 + attached patch: BB 4: 47 The benchmark result for 436.cactus only improves by about 2% since the first loop is not actually the "hottest" in the trio but the code is actually much better. I've not been able to measure the compile time overhead. Out of 10 measurements compiling the cactus testcase the minimum of the compile times was even lower then before. Perhaps having less instructions in the loop body made other passes faster. Overall I expect a very small compile time increase. Ok for mainline? Bye, -Andreas- 2011-07-11 Andreas Krebbel <andreas.kreb...@de.ibm.com> * passes.c (init_optimization_passes): Add invariant motion pass after induction variable optimization. Index: gcc/passes.c =================================================================== *** gcc/passes.c.orig --- gcc/passes.c *************** init_optimization_passes (void) *** 1363,1368 **** --- 1363,1369 ---- NEXT_PASS (pass_parallelize_loops); NEXT_PASS (pass_loop_prefetch); NEXT_PASS (pass_iv_optimize); + NEXT_PASS (pass_lim); NEXT_PASS (pass_tree_loop_done); } NEXT_PASS (pass_cse_reciprocals);
