#include "config.h"#include "system.h"#include "coretypes.h"#include "hash-table.h"#include "tm.h"#include "tree.h"#include "gimple-pretty-print.h"#include "bitmap.h"#include "sbitmap.h"#include "gimple.h"#include "gimple-ssa.h"#include "tree-phinodes.h"#include "ssa-iterators.h"#include "tree-ssanames.h"#include "tree-dfa.h"#include "timevar.h"#include "dumpfile.h"#include "tree-ssa-live.h"#include "diagnostic-core.h"#include "debug.h"#include "flags.h"
Data Structures | |
| struct | tree_int_map_hasher |
Variables | |
| static bitmap | usedvars |
| static bitmap_obstack | liveness_bitmap_obstack |
Function Documentation
| void calculate_live_on_exit | ( | ) |
Calculate the live on exit vectors based on the entry info in LIVEINFO.
live on entry calculations used liveout vectors for defs, clear them.
Set all the live-on-exit bits for uses in PHIs.
Mark the PHI arguments which are live on exit to the pred block.
Add each successors live on entry to this bock live on exit.
References NULL, NULL_TREE, _var_map::num_partitions, num_ssa_names, partition_to_var(), _var_map::partition_to_view, print_generic_expr(), TDF_SLIM, _var_map::var_partition, _var_map::view_to_partition, and virtual_operand_p().
| tree_live_info_p calculate_live_ranges | ( | ) |
Given partition map MAP, calculate all the live on entry bitmaps for each partition. Return a new live info object.
Referenced by coalesce_partitions().
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Set all block pointer in debug or clobber stmt to NULL if the block is unused, so that they will not be streamed out.
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Helper function for clear_unused_block_pointer, called via walk_tree.
| DEBUG_FUNCTION void debug | ( | ) |
Generic dump for the above.
| DEBUG_FUNCTION void debug_scope_block | ( | ) |
Dump the tree of lexical scopes starting at SCOPE to stderr. FLAGS is as in print_generic_expr.
| DEBUG_FUNCTION void debug_scope_blocks | ( | ) |
Dump the tree of lexical scopes of current_function_decl to stderr. FLAGS is as in print_generic_expr.
| void delete_tree_live_info | ( | ) |
Free storage for live range info object LIVE.
| void delete_var_map | ( | ) |
Free memory associated with MAP.
References gcc_assert, SSA_NAME_VERSION, TREE_CODE, and _var_map::var_partition.
| void dump_live_info | ( | ) |
Output live range info LIVE to file F, controlled by FLAG.
References bitmap_bit_p, cfun, edge_def::dest, EXIT_BLOCK_PTR, gimple_bb(), gimple_nop_p(), gimple_phi_arg_def(), gimple_phi_num_args(), gsi_end_p(), gsi_next(), gsi_start_phis(), gsi_stmt(), basic_block_def::index, live_on_entry(), NULL_TREE, num_var_partitions(), partition_to_var(), print_generic_expr(), print_gimple_stmt(), ssa_default_def(), SSA_NAME_DEF_STMT, SSA_NAME_VAR, and TDF_SLIM.
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Dump scope blocks starting at SCOPE to FILE. INDENT is the indentation level and FLAGS is as in print_generic_expr.
| void dump_scope_blocks | ( | ) |
Dump the tree of lexical scopes of current_function_decl to FILE. FLAGS is as in print_generic_expr.
| void dump_var_map | ( | ) |
Output partition map MAP to file F.
References EXECUTE_IF_SET_IN_BITMAP, FOR_EACH_BB, basic_block_def::index, tree_live_info_d::liveout, partition_to_var(), print_generic_expr(), and TDF_SLIM.
Referenced by coalesce_partitions().
| var_map init_var_map | ( | ) |
Create a variable partition map of SIZE, initialize and return it.
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Return true if VAR is marked as used.
References mark_all_vars_used(), NULL, TMR_BASE, TMR_INDEX, and TMR_INDEX2.
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Using LIVE, fill in all the live-on-entry blocks between the defs and uses of all the variables.
Visit all the blocks in reverse order and propagate live on entry values into the predecessors blocks.
Process any blocks which require further iteration.
References edge_def::src.
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Visit basic block BB and propagate any required live on entry bits from LIVE into the predecessors. VISITED is the bitmap of visited blocks. TMP is a temporary work bitmap which is passed in to avoid reallocating it each time.
TMP is variables live-on-entry from BB that aren't defined in the predecessor block. This should be the live on entry vars to pred. Note that liveout is the DEFs in a block while live on entry is being calculated.
Add these bits to live-on-entry for the pred. if there are any
changes, and pred_bb has been visited already, add it to the
revisit stack.
References bitmap_set_bit, ENTRY_BLOCK_PTR, FOR_EACH_IMM_USE_FAST, gimple_bb(), gimple_phi_arg_edge(), basic_block_def::index, tree_live_info_d::liveout, tree_live_info_d::map, NO_PARTITION, NULL, PHI_ARG_INDEX_FROM_USE, SSA_NAME_DEF_STMT, USE_STMT, and var_to_partition().
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Referenced by is_used_p().
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Mark all VAR_DECLS under *EXPR_P as used, so that they won't be eliminated during the tree->rtl conversion process.
References BLOCK_ABSTRACT, BLOCK_NUMBER, BLOCK_SOURCE_LOCATION, LOCATION_LOCUS, TREE_USED, and UNKNOWN_LOCATION.
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Helper function for mark_all_vars_used, called via walk_tree.
Ignore TMR_OFFSET and TMR_STEP for TARGET_MEM_REFS, as those fields do not contain vars.
Only need to mark VAR_DECLS; parameters and return results are not eliminated as unused.
When a global var becomes used for the first time also walk its
initializer (non global ones don't have any). remove_unused_scope_block_p requires information about labels which are not DECL_IGNORED_P to tell if they might be used in the IL.
Although the TREE_USED values that the frontend uses would be acceptable (albeit slightly over-conservative) for our purposes, init_vars_expansion clears TREE_USED for LABEL_DECLs too, so we must re-compute it here.
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Mark the scope block SCOPE and its subblocks unused when they can be possibly eliminated if dead.
References DECL_CHAIN.
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Allocate and return a new live range information object base on MAP.
| void partition_view_bitmap | ( | ) |
Create a partition view in MAP which includes just partitions which occur in the bitmap ONLY. If WANT_BASES is true, create the base variable map as well.
References bitmap_set_bit, and DECL_UID.
Referenced by coalesce_partitions().
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This routine will finalize the view data for MAP based on the partitions set in SELECTED. This is either the same bitmap returned from partition_view_init, or a trimmed down version if some of those partitions were not desired in this view. SELECTED is freed before returning.
If its a one-to-one ratio, we don't need any view compaction.
Give each selected partition an index.
References _var_map::partition_to_view, and _var_map::view_to_partition.
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Compress the partition numbers in MAP such that they fall in the range 0..(num_partitions-1) instead of wherever they turned out during the partitioning exercise. This removes any references to unused partitions, thereby allowing bitmaps and other vectors to be much denser.
This is implemented such that compaction doesn't affect partitioning. Ie., once partitions are created and possibly merged, running one or more different kind of compaction will not affect the partitions themselves. Their index might change, but all the same variables will still be members of the same partition group. This allows work on reduced sets, and no loss of information when a larger set is later desired.
In particular, coalescing can work on partitions which have 2 or more definitions, and then 'recompact' later to include all the single definitions for assignment to program variables. Set MAP back to the initial state of having no partition view. Return a bitmap which has a bit set for each partition number which is in use in the varmap.
Already in a view? Abandon the old one.
Find out which partitions are actually referenced.
| void partition_view_normal | ( | ) |
Create a partition view which includes all the used partitions in MAP. If WANT_BASES is true, create the base variable map as well.
| void remove_unused_locals | ( | void | ) |
Remove local variables that are not referenced in the IL.
Removing declarations from lexical blocks when not optimizing is not only a waste of time, it actually causes differences in stack layout.
Walk the CFG marking all referenced symbols.
Walk the statements.
We do a two-pass approach about the out-of-scope clobbers. We want to remove them if they are the only references to a local variable, but we want to retain them when there's any other. So the first pass ignores them, and the second pass (if there were any) tries to remove them.
Remove clobbers referencing unused vars, or clobbers
with MEM_REF lhs referencing uninitialized pointers. Remove unmarked local and global vars from local_decls.
Release any default def associated with var.
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Look if the block is dead (by possibly eliminating its dead subblocks) and return true if so. Block is declared dead if: 1) No statements are associated with it. 2) Declares no live variables 3) All subblocks are dead or there is precisely one subblocks and the block has same abstract origin as outer block and declares no variables, so it is pure wrapper. When we are not outputting full debug info, we also eliminate dead variables out of scope blocks to let them to be recycled by GGC and to save copying work done by the inliner.
Debug info of nested function refers to the block of the
function. We might stil call it even if all statements
of function it was nested into was elliminated.
TODO: We can actually look into cgraph to see if function
will be output to file.
If a decl has a value expr, we need to instantiate it
regardless of debug info generation, to avoid codegen
differences in memory overlap tests. update_equiv_regs() may
indirectly call validate_equiv_mem() to test whether a
SET_DEST overlaps with others, and if the value expr changes
by virtual register instantiation, we may get end up with
different results. Remove everything we don't generate debug info for.
When we are outputting debug info, we usually want to output
info about optimized-out variables in the scope blocks.
Exception are the scope blocks not containing any instructions
at all so user can't get into the scopes at first place. For labels that are still used in the IL, the decision to
preserve them must not depend DEBUG_INFO_LEVEL, otherwise we
risk having different ordering in debug vs. non-debug builds
during inlining or versioning.
A label appearing here (we have already checked DECL_IGNORED_P)
should not be used in the IL unless it has been explicitly used
before, so we use TREE_USED as an approximation. In principle, we should do the same here as for the debug case
below, however, when debugging, there might be additional nested
levels that keep an upper level with a label live, so we have to
force this block to be considered used, too. When we are not doing full debug info, we however can keep around
only the used variables for cfgexpand's memory packing saving quite
a lot of memory.
For sake of -g3, we keep around those vars but we don't count this as
use of block, so innermost block with no used vars and no instructions
can be considered dead. We only want to keep around blocks user can
breakpoint into and ask about value of optimized out variables.
Similarly we need to keep around types at least until all
variables of all nested blocks are gone. We track no
information on whether given type is used or not, so we have
to keep them even when not emitting debug information,
otherwise we may end up remapping variables and their (local)
types in different orders depending on whether debug
information is being generated. Outer scope is always used.
Innermost blocks with no live variables nor statements can be always eliminated.
For terse debug info we can eliminate info on unused variables.
Even for -g0/-g1 don't prune outer scopes from artificial
functions, otherwise diagnostics using tree_nonartificial_location
will not be emitted properly. See if this block is important for representation of inlined function. Inlined functions are always represented by block with block_ultimate_origin being set to FUNCTION_DECL and DECL_SOURCE_LOCATION set...
Verfify that only blocks with source location set are entry points to the inlined functions.
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Mark VAR as used, so that it'll be preserved during rtl expansion. Returns true if VAR wasn't marked before.
References NULL, and SSA_NAME_VAR.
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Calculate the initial live on entry vector for SSA_NAME using immediate_use links. Set the live on entry fields in LIVE. Def's are marked temporarily in the liveout vector.
Mark defs in liveout bitmap temporarily.
Visit each use of SSA_NAME and if it isn't in the same block as the def,
add it to the list of live on entry blocks.
Uses in PHI's are considered to be live at exit of the SRC block
as this is where a copy would be inserted. Check to see if it is
defined in that block, or whether its live on entry. If its not defined in this block, its live on entry.
If there was a live on entry use, set the bit.
If SSA_NAME is live on entry to at least one block, fill in all the live on entry blocks between the def and all the uses.
References bitmap_clear(), bitmap_ior_into(), bitmap_set_bit, edge_def::dest, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, FOR_EACH_BB, FOR_EACH_EDGE, gimple_phi_arg_edge(), gimple_phi_num_args(), gsi_end_p(), gsi_next(), gsi_start_phis(), gsi_stmt(), basic_block_def::index, live_on_entry(), tree_live_info_d::liveout, tree_live_info_d::map, NO_PARTITION, PHI_ARG_DEF, edge_def::src, basic_block_def::succs, TREE_CODE, and var_to_partition().
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Remove the base table in MAP.
Free the basevar info if it is present.
References map, NULL, _var_map::num_basevars, _var_map::num_partitions, _var_map::partition_size, _var_map::partition_to_view, _var_map::var_partition, and _var_map::view_to_partition.
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This routine will initialize the basevar fields of MAP.
We can have at most num_part entries in the hash tables, so it's enough to allocate so many map elements once, saving some malloc calls.
If a base table already exists, clear it, otherwise create it.
Build the base variable list, and point partitions at their bases.
This restricts what anonymous SSA names we can coalesce
as it restricts the sets we compute conflicts for.
Using TREE_TYPE to generate sets is the easies as
type equivalency also holds for SSA names with the same
underlying decl.
Check gimple_can_coalesce_p when changing this code. If base variable hasn't been seen, set it up.
| int var_union | ( | ) |
This function will combine the partitions in MAP for VAR1 and VAR2. It Returns the partition which represents the new partition. If the two partitions cannot be combined, NO_PARTITION is returned.
This is independent of partition_to_view. If partition_to_view is on, then whichever one of these partitions is absorbed will never have a dereference into the partition_to_view array any more.
Variable Documentation
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Obstack for globale liveness info bitmaps. We don't want to put these on the default obstack because these bitmaps can grow quite large and we'll hold on to all that memory until the end of the compiler run. As a bonus, delete_tree_live_info can destroy all the bitmaps by just releasing the whole obstack.
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