[PR111497][LRA]: Copy substituted equivalence

When we substitute the equivalence and it becomes shared, we can fail
to correctly update reg info used by LRA.  This can result in wrong
code generation, e.g. because of incorrect live analysis.  It can also
result in compiler crash as the pseudo survives RA.  This is what
exactly happened for the PR.  This patch solves this problem by
unsharing substituted equivalences.

gcc/ChangeLog:

	PR middle-end/111497
	* lra-constraints.cc (lra_constraints): Copy substituted
	equivalence.
	* lra.cc (lra): Change comment for calling unshare_all_rtl_again.

gcc/testsuite/ChangeLog:

	PR middle-end/111497
	* g++.target/i386/pr111497.C: new test.

(cherry picked from commit 3c23defed384cf17518ad6c817d94463a445d21b)

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index d92ab76908c8e07219ae9efd55eafbe76430e3f7..04b0b6fbfc2a1f60b8b87b80f9a62e64031eb10b 100644 (file)
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -5139,6 +5139,11 @@ lra_constraints (bool first_p)
                                           loc_equivalence_callback, curr_insn);
              if (old != *curr_id->operand_loc[0])
                {
+                 /* If we substitute pseudo by shared equivalence, we can fail
+                    to update LRA reg info and this can result in many
+                    unexpected consequences.  So keep rtl unshared:  */
+                 *curr_id->operand_loc[0]
+                   = copy_rtx (*curr_id->operand_loc[0]);
                  lra_update_insn_regno_info (curr_insn);
                  changed_p = true;
                }

diff --git a/gcc/lra.cc b/gcc/lra.cc
index 1444cb7591441ba9aae8274f283eb1c06db33938..5e29d3270d7d5079e7c7ac3de3ce240cc0de509b 100644 (file)
--- a/gcc/lra.cc
+++ b/gcc/lra.cc
@@ -2535,9 +2535,8 @@ lra (FILE *f)
   if (inserted_p)
     commit_edge_insertions ();
 
-  /* Replacing pseudos with their memory equivalents might have
-     created shared rtx.  Subsequent passes would get confused
-     by this, so unshare everything here.  */
+  /* Subsequent passes expect that rtl is unshared, so unshare everything
+     here.  */
   unshare_all_rtl_again (get_insns ());
 
   if (flag_checking)

diff --git a/gcc/testsuite/g++.target/i386/pr111497.C b/gcc/testsuite/g++.target/i386/pr111497.C
new file mode 100644 (file)
index 0000000..a645bb9
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr111497.C
@@ -0,0 +1,22 @@
+// { dg-do compile { target ia32 } }
+// { dg-options "-march=i686 -mtune=generic -fPIC -O2 -g" }
+
+class A;
+struct B { const char *b1; int b2; };
+struct C : B { C (const char *x, int y) { b1 = x; b2 = y; } };
+struct D : C { D (B x) : C (x.b1, x.b2) {} };
+struct E { E (A *); };
+struct F : E { D f1, f2, f3, f4, f5, f6; F (A *, const B &, const B &, const B &); };
+struct G : F { G (A *, const B &, const B &, const B &); };
+struct H { int h; };
+struct I { H i; };
+struct J { I *j; };
+struct A : J {};
+inline F::F (A *x, const B &y, const B &z, const B &w)
+  : E(x), f1(y), f2(z), f3(w), f4(y), f5(z), f6(w) {}
+G::G (A *x, const B &y, const B &z, const B &w) : F(x, y, z, w)
+{
+  H *h = &x->j->i;
+  if (h)
+    h->h++;
+}