Rangers Phi Analyzer was creating a group consisting of a single PHI,
which was problematic. It didn't really help anything, and it prevented
larger groups from including those PHIs and stopped some useful things
from happening.
Bootstrapped on x86_64-pc-linux-gnu with no regressions. Pushed.
Andrew
From 9855b3f0a2869d456f0ee34a94a1231eb6d44c4a Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacl...@redhat.com>
Date: Wed, 16 Aug 2023 13:23:06 -0400
Subject: [PATCH 1/4] Don't process phi groups with one phi.
The phi analyzer should not create a phi group containing a single phi.
* gimple-range-phi.cc (phi_analyzer::operator[]): Return NULL if
no group was created.
(phi_analyzer::process_phi): Do not create groups of one phi node.
---
gcc/gimple-range-phi.cc | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/gcc/gimple-range-phi.cc b/gcc/gimple-range-phi.cc
index ffb4691d06b..a94b90a4660 100644
--- a/gcc/gimple-range-phi.cc
+++ b/gcc/gimple-range-phi.cc
@@ -344,9 +344,10 @@ phi_analyzer::operator[] (tree name)
process_phi (as_a<gphi *> (SSA_NAME_DEF_STMT (name)));
if (bitmap_bit_p (m_simple, v))
return NULL;
- // If m_simple bit isn't set, then process_phi allocated the table
- // and should have a group.
- gcc_checking_assert (v < m_tab.length ());
+ // If m_simple bit isn't set, and process_phi didn't allocated the table
+ // no group was created, so return NULL.
+ if (v >= m_tab.length ())
+ return NULL;
}
return m_tab[v];
}
@@ -363,6 +364,7 @@ phi_analyzer::process_phi (gphi *phi)
unsigned x;
m_work.truncate (0);
m_work.safe_push (gimple_phi_result (phi));
+ unsigned phi_count = 1;
bitmap_clear (m_current);
// We can only have 2 externals: an initial value and a modifier.
@@ -407,6 +409,7 @@ phi_analyzer::process_phi (gphi *phi)
gimple *arg_stmt = SSA_NAME_DEF_STMT (arg);
if (arg_stmt && is_a<gphi *> (arg_stmt))
{
+ phi_count++;
m_work.safe_push (arg);
continue;
}
@@ -430,9 +433,12 @@ phi_analyzer::process_phi (gphi *phi)
}
}
- // If there are no names in the group, we're done.
- if (bitmap_empty_p (m_current))
+ // If there are less than 2 names, just return. This PHI may be included
+ // by another PHI, making it simple or a group of one will prevent a larger
+ // group from being formed.
+ if (phi_count < 2)
return;
+ gcc_checking_assert (!bitmap_empty_p (m_current));
phi_group *g = NULL;
if (cycle_p)
--
2.41.0
