So far all target implementations of the separate shrink-wrapping hooks
use the DF LIVE info to figure out around which basic blocks the non-
volatile registers need to be saved. This is done by looking at the
IN+GEN+KILL sets of the basic blocks. However, that doesn't work for
registers that DF says are defined in the entry block, or used in the
exit block.
This patch introduces a local flag DF_SCAN_EMPTY_ENTRY_EXIT that says
no registers should be defined in the entry block, and none used in the
exit block. It also makes try_shrink_wrapping_separate use it. The
rs6000 port is changed to use IN+GEN+KILL for the LR component.
Testing on powerpc64-linux {-m32,-m64}. Is this okay for trunk if that
succeeds?
Segher
2016-11-15 Segher Boessenkool <seg...@kernel.crashing.org>
* config/rs6000/rs6000.c (rs6000_components_for_bb): Mark the LR
component as used also if LR_REGNO is a live input to the bb.
* df-scan.c (df_get_entry_block_def_set): Return immediately after
clearing the set if DF_SCAN_EMPTY_ENTRY_EXIT is set.
(df_get_exit_block_use_set): Ditto.
* df.h (df_scan_flags): New enum.
* rtl.h (shrink_wrap_separate_in_progress): Declare new variable.
* shrink-wrap.c (try_shrink_wrapping_separate): Set
DF_SCAN_EMPTY_ENTRY_EXIT in df_scan->local_flags, and call
df_update_entry_block_defs and df_update_exit_block_uses
at the start; clear the flag and call those functions at the end.
---
gcc/config/rs6000/rs6000.c | 3 ++-
gcc/df-scan.c | 16 ++++++++++++++++
gcc/df.h | 7 +++++++
gcc/shrink-wrap.c | 19 +++++++++++++------
4 files changed, 38 insertions(+), 7 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 2ceddfd..d75d52c 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -27800,7 +27800,8 @@ rs6000_components_for_bb (basic_block bb)
bitmap_set_bit (components, regno);
/* LR needs to be saved around a bb if it is killed in that bb. */
- if (bitmap_bit_p (gen, LR_REGNO)
+ if (bitmap_bit_p (in, LR_REGNO)
+ || bitmap_bit_p (gen, LR_REGNO)
|| bitmap_bit_p (kill, LR_REGNO))
bitmap_set_bit (components, 0);
diff --git a/gcc/df-scan.c b/gcc/df-scan.c
index 7cfd34b..e6b55b5 100644
--- a/gcc/df-scan.c
+++ b/gcc/df-scan.c
@@ -3506,6 +3506,14 @@ df_get_entry_block_def_set (bitmap entry_block_defs)
bitmap_clear (entry_block_defs);
+ /* For separate shrink-wrapping we use LIVE to analyze which basic blocks
+ need a prologue for some component to be executed before that block,
+ and we do not care about any other registers. Hence, we do not want
+ any register for any component defined in the entry block, and we can
+ just leave all registers undefined. */
+ if (df_scan->local_flags & DF_SCAN_EMPTY_ENTRY_EXIT)
+ return;
+
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
{
if (global_regs[i])
@@ -3665,6 +3673,14 @@ df_get_exit_block_use_set (bitmap exit_block_uses)
bitmap_clear (exit_block_uses);
+ /* For separate shrink-wrapping we use LIVE to analyze which basic blocks
+ need an epilogue for some component to be executed after that block,
+ and we do not care about any other registers. Hence, we do not want
+ any register for any component seen as used in the exit block, and we
+ can just say no registers at all are used. */
+ if (df_scan->local_flags & DF_SCAN_EMPTY_ENTRY_EXIT)
+ return;
+
/* Stack pointer is always live at the exit. */
bitmap_set_bit (exit_block_uses, STACK_POINTER_REGNUM);
diff --git a/gcc/df.h b/gcc/df.h
index 40c3794..7a2a6a1 100644
--- a/gcc/df.h
+++ b/gcc/df.h
@@ -450,6 +450,13 @@ enum df_chain_flags
DF_UD_CHAIN = 2 /* Build UD chains. */
};
+enum df_scan_flags
+{
+ /* Flags for the SCAN problem. */
+ DF_SCAN_EMPTY_ENTRY_EXIT = 1 /* Don't define any registers in the entry
+ block; don't use any in the exit block. */
+};
+
enum df_changeable_flags
{
/* Scanning flags. */
diff --git a/gcc/shrink-wrap.c b/gcc/shrink-wrap.c
index e480d4d..f838696 100644
--- a/gcc/shrink-wrap.c
+++ b/gcc/shrink-wrap.c
@@ -1793,7 +1793,13 @@ try_shrink_wrapping_separate (basic_block first_bb)
if (!components)
return;
- /* We need LIVE info. */
+ /* We need LIVE info, not defining anything in the entry block and not
+ using anything in the exit block. A block then needs a component if
+ the register for that component is in the IN or GEN or KILL set for
+ that block. */
+ df_scan->local_flags |= DF_SCAN_EMPTY_ENTRY_EXIT;
+ df_update_entry_block_defs ();
+ df_update_exit_block_uses ();
df_live_add_problem ();
df_live_set_all_dirty ();
df_analyze ();
@@ -1859,9 +1865,10 @@ try_shrink_wrapping_separate (basic_block first_bb)
free_dominance_info (CDI_DOMINATORS);
free_dominance_info (CDI_POST_DOMINATORS);
- if (crtl->shrink_wrapped_separate)
- {
- df_live_set_all_dirty ();
- df_analyze ();
- }
+ /* All done. */
+ df_scan->local_flags &= ~DF_SCAN_EMPTY_ENTRY_EXIT;
+ df_update_entry_block_defs ();
+ df_update_exit_block_uses ();
+ df_live_set_all_dirty ();
+ df_analyze ();
}
--
1.9.3
