diff options
Diffstat (limited to 'gcc/tree-ssa-copy.c')
| -rw-r--r-- | gcc/tree-ssa-copy.c | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/gcc/tree-ssa-copy.c b/gcc/tree-ssa-copy.c index 986ad454e74..4b8d0b9660b 100644 --- a/gcc/tree-ssa-copy.c +++ b/gcc/tree-ssa-copy.c @@ -73,7 +73,7 @@ may_propagate_copy (tree dest, tree orig) if (TREE_CODE (dest) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)) return false; - + /* Do not copy between types for which we *do* need a conversion. */ if (!useless_type_conversion_p (type_d, type_o)) return false; @@ -351,7 +351,7 @@ get_last_copy_of (tree var) /* Traverse COPY_OF starting at VAR until we get to the last link in the chain. Since it is possible to have cycles in PHI nodes, the copy-of chain may also contain cycles. - + To avoid infinite loops and to avoid traversing lengthy copy-of chains, we artificially limit the maximum number of chains we are willing to traverse. @@ -390,7 +390,7 @@ set_copy_of_val (tree dest, tree first) { unsigned int dest_ver = SSA_NAME_VERSION (dest); tree old_first, old_last, new_last; - + /* Set FIRST to be the first link in COPY_OF[DEST]. If that changed, return true. */ old_first = copy_of[dest_ver].value; @@ -430,11 +430,11 @@ dump_copy_of (FILE *file, tree var) if (TREE_CODE (var) != SSA_NAME) return; - + visited = sbitmap_alloc (num_ssa_names); sbitmap_zero (visited); SET_BIT (visited, SSA_NAME_VERSION (var)); - + fprintf (file, " copy-of chain: "); val = var; @@ -458,7 +458,7 @@ dump_copy_of (FILE *file, tree var) fprintf (file, "[COPY]"); else fprintf (file, "[NOT A COPY]"); - + sbitmap_free (visited); } @@ -477,7 +477,7 @@ copy_prop_visit_assignment (gimple stmt, tree *result_p) lhs = gimple_assign_lhs (stmt); rhs = gimple_assign_rhs1 (stmt); - + gcc_assert (gimple_assign_rhs_code (stmt) == SSA_NAME); @@ -494,7 +494,7 @@ copy_prop_visit_assignment (gimple stmt, tree *result_p) copy of RHS's value, not of RHS itself. This avoids keeping unnecessary copy-of chains (assignments cannot be in a cycle like PHI nodes), speeding up the propagation process. - This is different from what we do in copy_prop_visit_phi_node. + This is different from what we do in copy_prop_visit_phi_node. In those cases, we are interested in the copy-of chains. */ *result_p = lhs; if (set_copy_of_val (*result_p, rhs_val->value)) @@ -820,7 +820,7 @@ fini_copy_prop (void) { size_t i; prop_value_t *tmp; - + /* Set the final copy-of value for each variable by traversing the copy-of chains. */ tmp = XCNEWVEC (prop_value_t, num_ssa_names); @@ -858,7 +858,7 @@ fini_copy_prop (void) /* Main entry point to the copy propagator. PHIS_ONLY is true if we should only consider PHI nodes as generating - copy propagation opportunities. + copy propagation opportunities. The algorithm propagates the value COPY-OF using ssa_propagate. For every variable X_i, COPY-OF(X_i) indicates which variable is X_i created @@ -881,7 +881,7 @@ fini_copy_prop (void) Visit #2: a_2 is copy-of x_298. Value changed. Visit #3: a_5 is copy-of x_298. Value changed. Visit #4: x_1 is copy-of x_298. Stable state reached. - + When visiting PHI nodes, we only consider arguments that flow through edges marked executable by the propagation engine. So, when visiting statement #2 for the first time, we will only look at @@ -918,7 +918,7 @@ fini_copy_prop (void) 1 x_54 = PHI <x_53, x_52> 2 x_53 = PHI <x_898, x_54> - + Visit #1: x_54 is copy-of x_53 (because x_52 is copy-of x_53) Visit #2: x_53 is copy-of x_898 (because x_54 is a copy of x_53, so it is considered irrelevant @@ -935,7 +935,7 @@ fini_copy_prop (void) same variable. So, as long as their copy-of chains overlap, we know that they will be a copy of the same variable, regardless of which variable that may be). - + Propagation would then proceed as follows (the notation a -> b means that a is a copy-of b): |