diff options
Diffstat (limited to 'gcc/tree-ssa-ifcombine.c')
| -rw-r--r-- | gcc/tree-ssa-ifcombine.c | 196 |
1 files changed, 126 insertions, 70 deletions
diff --git a/gcc/tree-ssa-ifcombine.c b/gcc/tree-ssa-ifcombine.c index 38d265f..be28fb0 100644 --- a/gcc/tree-ssa-ifcombine.c +++ b/gcc/tree-ssa-ifcombine.c @@ -135,6 +135,16 @@ bb_no_side_effects_p (basic_block bb) return true; } +/* Return true if BB is an empty forwarder block to TO_BB. */ + +static bool +forwarder_block_to (basic_block bb, basic_block to_bb) +{ + return empty_block_p (bb) + && single_succ_p (bb) + && single_succ (bb) == to_bb; +} + /* Verify if all PHI node arguments in DEST for edges from BB1 or BB2 to DEST are the same. This makes the CFG merge point free from side-effects. Return true in this case, else false. */ @@ -561,6 +571,99 @@ ifcombine_ifandif (basic_block inner_cond_bb, bool inner_inv, return false; } +/* Helper function for tree_ssa_ifcombine_bb. Recognize a CFG pattern and + dispatch to the appropriate if-conversion helper for a particular + set of INNER_COND_BB, OUTER_COND_BB, THEN_BB and ELSE_BB. + PHI_PRED_BB should be one of INNER_COND_BB, THEN_BB or ELSE_BB. */ + +static bool +tree_ssa_ifcombine_bb_1 (basic_block inner_cond_bb, basic_block outer_cond_bb, + basic_block then_bb, basic_block else_bb, + basic_block phi_pred_bb) +{ + /* The && form is characterized by a common else_bb with + the two edges leading to it mergable. The latter is + guaranteed by matching PHI arguments in the else_bb and + the inner cond_bb having no side-effects. */ + if (phi_pred_bb != else_bb + && recognize_if_then_else (outer_cond_bb, &inner_cond_bb, &else_bb) + && same_phi_args_p (outer_cond_bb, phi_pred_bb, else_bb) + && bb_no_side_effects_p (inner_cond_bb)) + { + /* We have + <outer_cond_bb> + if (q) goto inner_cond_bb; else goto else_bb; + <inner_cond_bb> + if (p) goto ...; else goto else_bb; + ... + <else_bb> + ... + */ + return ifcombine_ifandif (inner_cond_bb, false, outer_cond_bb, false, + false); + } + + /* And a version where the outer condition is negated. */ + if (phi_pred_bb != else_bb + && recognize_if_then_else (outer_cond_bb, &else_bb, &inner_cond_bb) + && same_phi_args_p (outer_cond_bb, phi_pred_bb, else_bb) + && bb_no_side_effects_p (inner_cond_bb)) + { + /* We have + <outer_cond_bb> + if (q) goto else_bb; else goto inner_cond_bb; + <inner_cond_bb> + if (p) goto ...; else goto else_bb; + ... + <else_bb> + ... + */ + return ifcombine_ifandif (inner_cond_bb, false, outer_cond_bb, true, + false); + } + + /* The || form is characterized by a common then_bb with the + two edges leading to it mergable. The latter is guaranteed + by matching PHI arguments in the then_bb and the inner cond_bb + having no side-effects. */ + if (phi_pred_bb != then_bb + && recognize_if_then_else (outer_cond_bb, &then_bb, &inner_cond_bb) + && same_phi_args_p (outer_cond_bb, phi_pred_bb, then_bb) + && bb_no_side_effects_p (inner_cond_bb)) + { + /* We have + <outer_cond_bb> + if (q) goto then_bb; else goto inner_cond_bb; + <inner_cond_bb> + if (q) goto then_bb; else goto ...; + <then_bb> + ... + */ + return ifcombine_ifandif (inner_cond_bb, true, outer_cond_bb, true, + true); + } + + /* And a version where the outer condition is negated. */ + if (phi_pred_bb != then_bb + && recognize_if_then_else (outer_cond_bb, &inner_cond_bb, &then_bb) + && same_phi_args_p (outer_cond_bb, phi_pred_bb, then_bb) + && bb_no_side_effects_p (inner_cond_bb)) + { + /* We have + <outer_cond_bb> + if (q) goto inner_cond_bb; else goto then_bb; + <inner_cond_bb> + if (q) goto then_bb; else goto ...; + <then_bb> + ... + */ + return ifcombine_ifandif (inner_cond_bb, true, outer_cond_bb, false, + true); + } + + return false; +} + /* Recognize a CFG pattern and dispatch to the appropriate if-conversion helper. We start with BB as the innermost worker basic-block. Returns true if a transformation was done. */ @@ -585,80 +688,33 @@ tree_ssa_ifcombine_bb (basic_block inner_cond_bb) { basic_block outer_cond_bb = single_pred (inner_cond_bb); - /* The && form is characterized by a common else_bb with - the two edges leading to it mergable. The latter is - guaranteed by matching PHI arguments in the else_bb and - the inner cond_bb having no side-effects. */ - if (recognize_if_then_else (outer_cond_bb, &inner_cond_bb, &else_bb) - && same_phi_args_p (outer_cond_bb, inner_cond_bb, else_bb) - && bb_no_side_effects_p (inner_cond_bb)) - { - /* We have - <outer_cond_bb> - if (q) goto inner_cond_bb; else goto else_bb; - <inner_cond_bb> - if (p) goto ...; else goto else_bb; - ... - <else_bb> - ... - */ - return ifcombine_ifandif (inner_cond_bb, false, outer_cond_bb, false, - false); - } + if (tree_ssa_ifcombine_bb_1 (inner_cond_bb, outer_cond_bb, + then_bb, else_bb, inner_cond_bb)) + return true; - /* And a version where the outer condition is negated. */ - if (recognize_if_then_else (outer_cond_bb, &else_bb, &inner_cond_bb) - && same_phi_args_p (outer_cond_bb, inner_cond_bb, else_bb) - && bb_no_side_effects_p (inner_cond_bb)) + if (forwarder_block_to (else_bb, then_bb)) { - /* We have - <outer_cond_bb> - if (q) goto else_bb; else goto inner_cond_bb; - <inner_cond_bb> - if (p) goto ...; else goto else_bb; - ... - <else_bb> - ... - */ - return ifcombine_ifandif (inner_cond_bb, false, outer_cond_bb, true, - false); + /* Other possibilities for the && form, if else_bb is + empty forwarder block to then_bb. Compared to the above simpler + forms this can be treated as if then_bb and else_bb were swapped, + and the corresponding inner_cond_bb not inverted because of that. + For same_phi_args_p we look at equality of arguments between + edge from outer_cond_bb and the forwarder block. */ + if (tree_ssa_ifcombine_bb_1 (inner_cond_bb, outer_cond_bb, else_bb, + then_bb, else_bb)) + return true; } - - /* The || form is characterized by a common then_bb with the - two edges leading to it mergable. The latter is guaranteed - by matching PHI arguments in the then_bb and the inner cond_bb - having no side-effects. */ - if (recognize_if_then_else (outer_cond_bb, &then_bb, &inner_cond_bb) - && same_phi_args_p (outer_cond_bb, inner_cond_bb, then_bb) - && bb_no_side_effects_p (inner_cond_bb)) - { - /* We have - <outer_cond_bb> - if (q) goto then_bb; else goto inner_cond_bb; - <inner_cond_bb> - if (q) goto then_bb; else goto ...; - <then_bb> - ... - */ - return ifcombine_ifandif (inner_cond_bb, true, outer_cond_bb, true, - true); - } - - /* And a version where the outer condition is negated. */ - if (recognize_if_then_else (outer_cond_bb, &inner_cond_bb, &then_bb) - && same_phi_args_p (outer_cond_bb, inner_cond_bb, then_bb) - && bb_no_side_effects_p (inner_cond_bb)) + else if (forwarder_block_to (then_bb, else_bb)) { - /* We have - <outer_cond_bb> - if (q) goto inner_cond_bb; else goto then_bb; - <inner_cond_bb> - if (q) goto then_bb; else goto ...; - <then_bb> - ... - */ - return ifcombine_ifandif (inner_cond_bb, true, outer_cond_bb, false, - true); + /* Other possibilities for the || form, if then_bb is + empty forwarder block to else_bb. Compared to the above simpler + forms this can be treated as if then_bb and else_bb were swapped, + and the corresponding inner_cond_bb not inverted because of that. + For same_phi_args_p we look at equality of arguments between + edge from outer_cond_bb and the forwarder block. */ + if (tree_ssa_ifcombine_bb_1 (inner_cond_bb, outer_cond_bb, else_bb, + then_bb, then_bb)) + return true; } } |