[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.

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 3aaa49069997c1d771a0ced82c9be1f4bf23fed1..76a1393ab23e7982ab9a51c4de48f3e4b32da881 100644 (file)
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -5424,6 +5424,11 @@ 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 563aff10b9658b5a26dfeaad741633aaf7df009c..361f84fdacb65cef8c1bf4c1bed2aad1e559da65 100644 (file)
--- a/gcc/lra.cc
+++ b/gcc/lra.cc
@@ -2579,9 +2579,8 @@ 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++;
+}