procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Abstract PHI and forwarder block checks in jump threader.

Browse source 
This patch abstracts out a couple common idioms in the forward
threader that I found useful while navigating the code base.

Tested on x86-64 Linux.

gcc/ChangeLog:

	* tree-ssa-threadedge.c (has_phis_p): New.
	(forwarder_block_p): New.
	(potentially_threadable_block): Call forwarder_block_p.
	(jump_threader::thread_around_empty_blocks): Call has_phis_p.
	(jump_threader::thread_through_normal_block): Call
	forwarder_block_p.
This commit is contained in:
Aldy Hernandez 2021-09-03 11:55:11 +02:00
parent 779275c083
commit 62099645c2
1 changed files with 19 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
gcc/tree-ssa-threadedge.c
View file

@ -95,6 +95,21 @@ jump_threader::thread_through_all_blocks (bool may_peel_loop_headers)
return m_registry->thread_through_all_blocks (may_peel_loop_headers);
}
static inline bool
has_phis_p (basic_block bb)
{
return !gsi_end_p (gsi_start_phis (bb));
}
/* Return TRUE for a forwarder block which is defined as having PHIs
but no instructions. */
static bool
forwarder_block_p (basic_block bb)
{
return gsi_end_p (gsi_start_nondebug_bb (bb)) && has_phis_p (bb);
}
/* Return TRUE if we may be able to thread an incoming edge into
BB to an outgoing edge from BB. Return FALSE otherwise. */
@ -107,9 +122,8 @@ potentially_threadable_block (basic_block bb)
not optimized away because they forward from outside a loop
to the loop header. We want to thread through them as we can
sometimes thread to the loop exit, which is obviously profitable.
the interesting case here is when the block has PHIs. */
if (gsi_end_p (gsi_start_nondebug_bb (bb))
&& !gsi_end_p (gsi_start_phis (bb)))
The interesting case here is when the block has PHIs. */
if (forwarder_block_p (bb))
return true;
/* If BB has a single successor or a single predecessor, then
@ -854,7 +868,7 @@ jump_threader::thread_around_empty_blocks (vec<jump_thread_edge *> *path,
/* The key property of these blocks is that they need not be duplicated
when threading. Thus they cannot have visible side effects such
as PHI nodes. */
if (!gsi_end_p (gsi_start_phis (bb)))
if (has_phis_p (bb))
return false;
/* Skip over DEBUG statements at the start of the block. */
@ -994,8 +1008,7 @@ jump_threader::thread_through_normal_block (vec<jump_thread_edge *> *path,
{
/* First case. The statement simply doesn't have any instructions, but
does have PHIs. */
if (gsi_end_p (gsi_start_nondebug_bb (e->dest))
&& !gsi_end_p (gsi_start_phis (e->dest)))
if (forwarder_block_p (e->dest))
return 0;
/* Second case. */