[SFN+LVU+IEPM v4 9/9] [IEPM] Introduce inline entry point markers
Alexandre Oliva
aoliva@redhat.com
Wed Feb 21 10:33:00 GMT 2018
On Jan 24, 2018, Jakub Jelinek <jakub@redhat.com> wrote:
>> --- a/gcc/tree-ssa-live.c
>> +++ b/gcc/tree-ssa-live.c
>> @@ -520,6 +520,11 @@ remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
>> else if (!BLOCK_SUPERCONTEXT (scope)
>> || TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL)
>> unused = false;
>> + /* Preserve the block, it is referenced by at least the inline
>> + entry point marker. */
>> + else if (debug_nonbind_markers_p
>> + && inlined_function_outer_scope_p (scope))
>> + unused = false;
>> /* Innermost blocks with no live variables nor statements can be always
>> eliminated. */
>> else if (!nsubblocks)
>> @@ -548,11 +553,13 @@ remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
>> }
>> else if (BLOCK_VARS (scope) || BLOCK_NUM_NONLOCALIZED_VARS (scope))
>> unused = false;
>> - /* 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... */
>> - else if (inlined_function_outer_scope_p (scope))
>> + /* 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, unless they expand to nothing... But
>> + see above for the case of statement frontiers. */
>> + else if (!debug_nonbind_markers_p
>> + && inlined_function_outer_scope_p (scope))
>> unused = false;
> Wonder what the above hunks will do for LTO memory consumption. We'll see.
[IEPM] don't preserve lexical blocks just for debug inline markers
This patch stops preserving scope blocks just because they are inlined
function scopes, when cleaning up unused scope blocks. This change
was introduced along with IEPM, but it preserved lots of blocks, and
output debug information for them, although no code from the inlined
function remained after optimization.
The additional preserved blocks took up compile-time memory, and
significant disk space and link time, in some cases more than 25%.
This is deemed excessive, compared with the reasonably small benefit
of allowing one to single-step into an inlined function using a
view-capable debugger.
There was another way of marking inlined function scopes as unused,
based on the markers referencing them during stmt scanning, but that
still preserved too much.
So, this patch restores the pre-IEPM logic of preservation of scopes.
Should a scope block referenced by an inline entry marker be found to
be unused in remove_unused_scope_block_p, the marker will be cleaned
up right after that, in clear_unused_block_pointer, so we won't keep
a dangling reference to a dropped block.
Regstrapped on x86_64- and i686-linux-gnu. Ok to install?
for gcc/ChangeLog
* tree-ssa-live.c (remove_unused_scope_block_p): Do not
preserve inline entry blocks for the sake of debug inline
entry point markers alone.
(remove_unused_locals): Suggest in comments a better place to
force the preservation of inline entry blocks that are
otherwise unused, but do not preserve them.
---
gcc/tree-ssa-live.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/gcc/tree-ssa-live.c b/gcc/tree-ssa-live.c
index 62bb3c5de659..62316bac7929 100644
--- a/gcc/tree-ssa-live.c
+++ b/gcc/tree-ssa-live.c
@@ -520,11 +520,6 @@ remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
else if (!BLOCK_SUPERCONTEXT (scope)
|| TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL)
unused = false;
- /* Preserve the block, it is referenced by at least the inline
- entry point marker. */
- else if (debug_inline_points
- && inlined_function_outer_scope_p (scope))
- unused = false;
/* Innermost blocks with no live variables nor statements can be always
eliminated. */
else if (!nsubblocks)
@@ -556,10 +551,8 @@ remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
/* 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, unless they expand to nothing... But
- see above for the case of statement frontiers. */
- else if (!debug_inline_points
- && inlined_function_outer_scope_p (scope))
+ DECL_SOURCE_LOCATION set, unless they expand to nothing... */
+ else if (inlined_function_outer_scope_p (scope))
unused = false;
else
/* Verfify that only blocks with source location set
@@ -741,6 +734,10 @@ remove_unused_locals (void)
gimple *stmt = gsi_stmt (gsi);
tree b = gimple_block (stmt);
+ /* If we wanted to mark the block referenced by the inline
+ entry point marker as used, this would be a good spot to
+ do it. If the block is not otherwise used, the stmt will
+ be cleaned up in clean_unused_block_pointer. */
if (is_gimple_debug (stmt))
continue;
Here's a patch I'm sharing just FTR, that introduces (on top of the
above) options to select other approaches to preserve scopes related
with inlined functions. It's not meant for inclusion; the options'
spelling are such that the three possible approaches, as well as
-gno-inline-points, can be tested so as to compare file sizes to measure
debug info size changes, without noise out of different length of the
command-line options.
The differences in libgcc are tiny, but those in cc1 and cc1plus are
quite significant:
no df mr al
cc1 260726424 280455288 312591944 312600224
cc1plus 289090200 309719888 347144256 347152840
libgcc_s.so 864016 867840 868128 868128
libstdc++.so 12846528 14758400 17619736 17619480
---
gcc/common.opt | 12 ++++++++++++
gcc/tree-ssa-live.c | 5 ++++-
2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/gcc/common.opt b/gcc/common.opt
index e0bc4d1bb18d..594ea0213cba 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2924,6 +2924,18 @@ ginline-points
Common Driver Var(debug_inline_points) Init(2)
Generate extended entry point information for inlined functions
+ginline-points=df
+Common Driver Var(debug_inline_points, 1) Init(2)
+Don't preserve blocks just for inlined functions
+
+ginline-points=al
+Common Driver Var(debug_inline_points, 3) Init(2)
+Preserve all blocks regarded as inlined function scopes
+
+ginline-points=mr
+Common Driver Var(debug_inline_points, 4) Init(2)
+Preserve blocks referenced by inline entry point markers only
+
ginternal-reset-location-views
Common Driver Var(debug_internal_reset_location_views) Init(2)
Compute locview reset points based on insn length estimates
diff --git a/gcc/tree-ssa-live.c b/gcc/tree-ssa-live.c
index 62316bac7929..f75a6ea2126a 100644
--- a/gcc/tree-ssa-live.c
+++ b/gcc/tree-ssa-live.c
@@ -520,6 +520,8 @@ remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
else if (!BLOCK_SUPERCONTEXT (scope)
|| TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL)
unused = false;
+ else if (debug_inline_points == 3 && inlined_function_outer_scope_p (scope))
+ unused = false;
/* Innermost blocks with no live variables nor statements can be always
eliminated. */
else if (!nsubblocks)
@@ -738,7 +740,8 @@ remove_unused_locals (void)
entry point marker as used, this would be a good spot to
do it. If the block is not otherwise used, the stmt will
be cleaned up in clean_unused_block_pointer. */
- if (is_gimple_debug (stmt))
+ if (is_gimple_debug (stmt)
+ && (debug_inline_points != 4 || !gimple_debug_inline_entry_p (stmt)))
continue;
if (gimple_clobber_p (stmt))
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer
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