[gcc r13-7949] Do not add partial equivalences with no uses.

[Andrew Macleod <amacleod@gcc.gnu.org>]

https://gcc.gnu.org/g:1c2bd0839e3574ab2a76ec18faf906b2f64b5f81

commit r13-7949-g1c2bd0839e3574ab2a76ec18faf906b2f64b5f81
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Thu Oct 12 17:06:36 2023 -0400

    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.

Diff:
---
 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)