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re PR tree-optimization/69196 (code size regression with jump threading at -O2)

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PR tree-optimization/69196
	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
	Do count some PHIs in the thread path against the insn count.  Decrease
	final statement count by one as the control statement in the last
	block will get removed.  Remove special cased code for handling PHIs		in the last block.

	PR tree-optimization/69196
	* gcc.dg/tree-ssa/vrp46.c: Twiddle threading params to keep it from
	duplicating code and spoiling the expected output.

From-SVN: r233866
This commit is contained in:
Jeff Law 2016-03-01 14:46:58 -07:00 committed by Jeff Law
parent 0d39977e34
commit 2a9afc8680
4 changed files with 51 additions and 19 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2016-03-01 Jeff Law <law@redhat.com>
PR tree-optimization/69196
* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
Do count some PHIs in the thread path against the insn count. Decrease
final statement count by one as the control statement in the last
block will get removed. Remove special cased code for handling PHIs in the last block.
2016-03-01 Uros Bizjak <ubizjak@gmail.com>
PR target/70027

6
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,9 @@
2016-03-01 Jeff Law <law@redhat.com>
PR tree-optimization/69196
* gcc.dg/tree-ssa/vrp46.c: Twiddle threading params to keep it from
duplicating code and spoiling the expected output.
2016-03-01 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/70033

2
gcc/testsuite/gcc.dg/tree-ssa/vrp46.c
View File

@ -1,5 +1,5 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-vrp1" } */
/* { dg-options "-O2 -fdump-tree-vrp1 --param fsm-scale-path-blocks=1" } */
int func_81 (int);
int func_98 (int);

54
gcc/tree-ssa-threadbackward.c
View File

@ -286,6 +286,37 @@ fsm_find_control_statement_thread_paths (tree name,
break;
}
/* PHIs in the path will create degenerate PHIS in the
copied path which will then get propagated away, so
looking at just the duplicate path the PHIs would
seem unimportant.
But those PHIs, because they're assignments to objects
typically with lives that exist outside the thread path,
will tend to generate PHIs (or at least new PHI arguments)
at points where we leave the thread path and rejoin
the original blocks. So we do want to account for them.
We ignore virtual PHIs. We also ignore cases where BB
has a single incoming edge. That's the most common
degenerate PHI we'll see here. Finally we ignore PHIs
that are associated with the value we're tracking as
that object likely dies. */
if (EDGE_COUNT (bb->succs) > 1 && EDGE_COUNT (bb->preds) > 1)
{
for (gphi_iterator gsip = gsi_start_phis (bb);
!gsi_end_p (gsip);
gsi_next (&gsip))
{
gphi *phi = gsip.phi ();
tree dst = gimple_phi_result (phi);
if (SSA_NAME_VAR (dst) != SSA_NAME_VAR (name)
&& !virtual_operand_p (dst))
++n_insns;
}
}
for (gsi = gsi_after_labels (bb);
!gsi_end_p (gsi);
gsi_next_nondebug (&gsi))
@ -324,6 +355,11 @@ fsm_find_control_statement_thread_paths (tree name,
threaded_through_latch = true;
}
/* We are going to remove the control statement at the end of the
last block in the threading path. So don't count it against our
statement count. */
n_insns--;
gimple *stmt = get_gimple_control_stmt ((*path)[0]);
gcc_assert (stmt);
/* We have found a constant value for ARG. For GIMPLE_SWITCH
@ -352,24 +388,6 @@ fsm_find_control_statement_thread_paths (tree name,
== DOMST_NONDOMINATING))
creates_irreducible_loop = true;
/* PHIs in the final target and only the final target will need
to be duplicated. So only count those against the number
of statements. */
gphi_iterator gsip;
for (gsip = gsi_start_phis (taken_edge->dest);
!gsi_end_p (gsip);
gsi_next (&gsip))
{
gphi *phi = gsip.phi ();
tree dst = gimple_phi_result (phi);
/* We consider any non-virtual PHI as a statement since it
count result in a constant assignment or copy
operation. */
if (!virtual_operand_p (dst))
++n_insns;
}
if (path_crosses_loops)
{
if (dump_file && (dump_flags & TDF_DETAILS))