diff options
Diffstat (limited to 'gcc/tree-ssa-operands.c')
| -rw-r--r-- | gcc/tree-ssa-operands.c | 248 |
1 files changed, 247 insertions, 1 deletions
diff --git a/gcc/tree-ssa-operands.c b/gcc/tree-ssa-operands.c index c92c0e72a2c..cac13ebf469 100644 --- a/gcc/tree-ssa-operands.c +++ b/gcc/tree-ssa-operands.c @@ -121,6 +121,49 @@ static void get_expr_operands (tree, tree *, int); /* Number of functions with initialized ssa_operands. */ static int n_initialized = 0; +/* Statement change buffer. Data structure used to record state + information for statements. This is used to determine what needs + to be done in order to update the SSA web after a statement is + modified by a pass. If STMT is a statement that has just been + created, or needs to be folded via fold_stmt, or anything that + changes its physical structure then the pass should: + + 1- Call push_stmt_changes (&stmt) to record the current state of + STMT before any modifications are made. + + 2- Make all appropriate modifications to the statement. + + 3- Call pop_stmt_changes (&stmt) to find new symbols that + need to be put in SSA form, SSA name mappings for names that + have disappeared, recompute invariantness for address + expressions, cleanup EH information, etc. + + If it is possible to determine that the statement was not modified, + instead of calling pop_stmt_changes it is quicker to call + discard_stmt_changes to avoid the expensive and unnecessary operand + re-scan and change comparison. */ + +struct scb_d +{ + /* Pointer to the statement being modified. */ + tree *stmt_p; + + /* If the statement references memory these are the sets of symbols + loaded and stored by the statement. */ + bitmap loads; + bitmap stores; +}; + +typedef struct scb_d *scb_t; +DEF_VEC_P(scb_t); +DEF_VEC_ALLOC_P(scb_t,heap); + +/* Stack of statement change buffers (SCB). Every call to + push_stmt_changes pushes a new buffer onto the stack. Calls to + pop_stmt_changes pop a buffer off of the stack and compute the set + of changes for the popped statement. */ +static VEC(scb_t,heap) *scb_stack; + /* Allocates operand OP of given TYPE from the appropriate free list, or of the new value if the list is empty. */ @@ -2277,7 +2320,7 @@ copy_virtual_operands (tree dest, tree src) values stored. */ void -create_ssa_artficial_load_stmt (tree new_stmt, tree old_stmt) +create_ssa_artificial_load_stmt (tree new_stmt, tree old_stmt) { stmt_ann_t ann; tree op; @@ -2567,3 +2610,206 @@ debug_immediate_uses_for (tree var) { dump_immediate_uses_for (stderr, var); } + + +/* Create a new change buffer for the statement pointed by STMT_P and + push the buffer into SCB_STACK. Each change buffer + records state information needed to determine what changed in the + statement. Mainly, this keeps track of symbols that may need to be + put into SSA form, SSA name replacements and other information + needed to keep the SSA form up to date. */ + +void +push_stmt_changes (tree *stmt_p) +{ + tree stmt; + scb_t buf; + + stmt = *stmt_p; + + /* It makes no sense to keep track of PHI nodes. */ + if (TREE_CODE (stmt) == PHI_NODE) + return; + + buf = xmalloc (sizeof *buf); + memset (buf, 0, sizeof *buf); + + buf->stmt_p = stmt_p; + + if (stmt_references_memory_p (stmt)) + { + tree op; + ssa_op_iter i; + + FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_VUSE) + { + tree sym = TREE_CODE (op) == SSA_NAME ? SSA_NAME_VAR (op) : op; + if (buf->loads == NULL) + buf->loads = BITMAP_ALLOC (NULL); + bitmap_set_bit (buf->loads, DECL_UID (sym)); + } + + FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_VIRTUAL_DEFS) + { + tree sym = TREE_CODE (op) == SSA_NAME ? SSA_NAME_VAR (op) : op; + if (buf->stores == NULL) + buf->stores = BITMAP_ALLOC (NULL); + bitmap_set_bit (buf->stores, DECL_UID (sym)); + } + } + + VEC_safe_push (scb_t, heap, scb_stack, buf); +} + + +/* Given two sets S1 and S2, mark the symbols that differ in S1 and S2 + for renaming. The set to mark for renaming is (S1 & ~S2) | (S2 & ~S1). */ + +static void +mark_difference_for_renaming (bitmap s1, bitmap s2) +{ + if (s1 == NULL && s2 == NULL) + return; + + if (s1 && s2 == NULL) + mark_set_for_renaming (s1); + else if (s1 == NULL && s2) + mark_set_for_renaming (s2); + else if (!bitmap_equal_p (s1, s2)) + { + bitmap t1 = BITMAP_ALLOC (NULL); + bitmap t2 = BITMAP_ALLOC (NULL); + + bitmap_and_compl (t1, s1, s2); + bitmap_and_compl (t2, s2, s1); + bitmap_ior_into (t1, t2); + mark_set_for_renaming (t1); + + BITMAP_FREE (t1); + BITMAP_FREE (t2); + } +} + + +/* Pop the top SCB from SCB_STACK and act on the differences between + what was recorded by push_stmt_changes and the current state of + the statement. */ + +void +pop_stmt_changes (tree *stmt_p) +{ + tree op, stmt; + ssa_op_iter iter; + bitmap loads, stores; + scb_t buf; + + stmt = *stmt_p; + + /* It makes no sense to keep track of PHI nodes. */ + if (TREE_CODE (stmt) == PHI_NODE) + return; + + buf = VEC_pop (scb_t, scb_stack); + gcc_assert (stmt_p == buf->stmt_p); + + /* Force an operand re-scan on the statement and mark any newly + exposed variables. */ + update_stmt (stmt); + + /* Determine whether any memory symbols need to be renamed. If the + sets of loads and stores are different after the statement is + modified, then the affected symbols need to be renamed. + + Note that it may be possible for the statement to not reference + memory anymore, but we still need to act on the differences in + the sets of symbols. */ + loads = stores = NULL; + if (stmt_references_memory_p (stmt)) + { + tree op; + ssa_op_iter i; + + FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_VUSE) + { + tree sym = TREE_CODE (op) == SSA_NAME ? SSA_NAME_VAR (op) : op; + if (loads == NULL) + loads = BITMAP_ALLOC (NULL); + bitmap_set_bit (loads, DECL_UID (sym)); + } + + FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_VIRTUAL_DEFS) + { + tree sym = TREE_CODE (op) == SSA_NAME ? SSA_NAME_VAR (op) : op; + if (stores == NULL) + stores = BITMAP_ALLOC (NULL); + bitmap_set_bit (stores, DECL_UID (sym)); + + /* If a V_MAY_DEF turned into a V_MUST_DEF, we will keep + referencing the same symbol, but we still need to mark it + for renaming since the operand scanner stripped its + SSA_NAME. */ + if (op == sym) + mark_sym_for_renaming (sym); + } + } + + /* If LOADS is different from BUF->LOADS, the affected + symbols need to be marked for renaming. */ + mark_difference_for_renaming (loads, buf->loads); + + /* Similarly for STORES and BUF->STORES. */ + mark_difference_for_renaming (stores, buf->stores); + + /* Mark all the naked GIMPLE register operands for renaming. */ + FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF|SSA_OP_USE) + if (DECL_P (op)) + mark_sym_for_renaming (op); + + /* FIXME, need to add more finalizers here. Cleanup EH info, + recompute invariants for address expressions, add + SSA replacement mappings, etc. For instance, given + testsuite/gcc.c-torture/compile/pr16808.c, we fold a statement of + the form: + + # SMT.4_20 = VDEF <SMT.4_16> + D.1576_11 = 1.0e+0; + + So, the VDEF will disappear, but instead of marking SMT.4 for + renaming it would be far more efficient to establish a + replacement mapping that would replace every reference of + SMT.4_20 with SMT.4_16. */ + + /* Free memory used by the buffer. */ + BITMAP_FREE (buf->loads); + BITMAP_FREE (buf->stores); + BITMAP_FREE (loads); + BITMAP_FREE (stores); + buf->stmt_p = NULL; + free (buf); +} + + +/* Discard the topmost change buffer from SCB_STACK. This is useful + when the caller realized that it did not actually modified the + statement. It avoids the expensive operand re-scan. */ + +void +discard_stmt_changes (tree *stmt_p) +{ + scb_t buf; + tree stmt; + + /* It makes no sense to keep track of PHI nodes. */ + stmt = *stmt_p; + if (TREE_CODE (stmt) == PHI_NODE) + return; + + buf = VEC_pop (scb_t, scb_stack); + gcc_assert (stmt_p == buf->stmt_p); + + /* Free memory used by the buffer. */ + BITMAP_FREE (buf->loads); + BITMAP_FREE (buf->stores); + buf->stmt_p = NULL; + free (buf); +} |