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[COMMITTED,GCC13] PR tree-optimization/111622 - Do not add partial equivalences with no uses.

Message ID 72519953-7b2c-5156-485d-75904da5a90a@redhat.com
State New
Headers show
Series [COMMITTED,GCC13] PR tree-optimization/111622 - Do not add partial equivalences with no uses. | expand

Commit Message

Andrew MacLeod Oct. 13, 2023, 1:24 p.m. UTC 
There are a lot of dead statements in this testcase which a casts. These 
were being added to the list of partial equivalences and causing some 
serious compile time issues.

Rangers cache loops through equivalences when its propagating on-entry 
values, so if the partial equivalence list is very large, it can consume 
a lot of time.  Typically, partial equivalence lists are small.   In 
this case, a lot of dead stmts were not removed, so there was no 
redundancy elimination and it was causing an issue.

Bootstrapped on x86_64-pc-linux-gnu with no regressions. Pushed.

Andrew
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Patch

From 425964b77ab5b9631e914965a7397303215c77a1 Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Thu, 12 Oct 2023 17:06:36 -0400
Subject: [PATCH] Do not add partial equivalences with no uses.

	PR tree-optimization/111622
	* value-relation.cc (equiv_oracle::add_partial_equiv): Do not
	register a partial equivalence if an operand has no uses.
---
 gcc/value-relation.cc | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
index fc792a4d5bc..0ed5f93d184 100644
--- a/gcc/value-relation.cc
+++ b/gcc/value-relation.cc
@@ -389,6 +389,9 @@  equiv_oracle::add_partial_equiv (relation_kind r, tree op1, tree op2)
       // In either case, if PE2 has an entry, we simply do nothing.
       if (pe2.members)
 	return;
+      // If there are no uses of op2, do not register.
+      if (has_zero_uses (op2))
+	return;
       // PE1 is the LHS and already has members, so everything in the set
       // should be a slice of PE2 rather than PE1.
       pe2.code = pe_min (r, pe1.code);
@@ -406,6 +409,9 @@  equiv_oracle::add_partial_equiv (relation_kind r, tree op1, tree op2)
     }
   if (pe2.members)
     {
+      // If there are no uses of op1, do not register.
+      if (has_zero_uses (op1))
+	return;
       pe1.ssa_base = pe2.ssa_base;
       // If pe2 is a 16 bit value, but only an 8 bit copy, we can't be any
       // more than an 8 bit equivalence here, so choose MIN value.
@@ -415,6 +421,9 @@  equiv_oracle::add_partial_equiv (relation_kind r, tree op1, tree op2)
     }
   else
     {
+      // If there are no uses of either operand, do not register.
+      if (has_zero_uses (op1) || has_zero_uses (op2))
+	return;
       // Neither name has an entry, simply create op1 as slice of op2.
       pe2.code = bits_to_pe (TYPE_PRECISION (TREE_TYPE (op2)));
       if (pe2.code == VREL_VARYING)
-- 
2.41.0