tree-optimization/100278 - handle mismatched code in TBAA adjust of PRE

PRE has code to adjust TBAA behavior for refs that expects the base
operation code to match.  The testcase shows a case where we have
a VAR_DECL vs. a MEM_REF so add code to give up in such cases.

2021-04-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100278
	* tree-ssa-pre.c (compute_avail): Give up when we cannot
	adjust TBAA beacuse of mismatching bases.

	* gcc.dg/tree-ssa/pr100278.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr100278.c b/gcc/testsuite/gcc.dg/tree-ssa/pr100278.c
new file mode 100644 (file)
index 0000000..8d70228
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr100278.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void a()
+{
+#if defined __s390__
+  register int b asm("r5");
+#elif defined __x86_64__
+  register int b asm("eax");
+#else
+  volatile int b;
+#endif
+  if (b)
+    b = 1;
+  for (; b;)
+    ;
+}

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 2803b58..2d22535 100644 (file)
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -4151,6 +4151,16 @@ compute_avail (void)
                      if (ref->set == set
                          || alias_set_subset_of (set, ref->set))
                        ;
+                     else if (ref1->opcode != ref2->opcode
+                              || (ref1->opcode != MEM_REF
+                                  && ref1->opcode != TARGET_MEM_REF))
+                       {
+                         /* With mismatching base opcodes or bases
+                            other than MEM_REF or TARGET_MEM_REF we
+                            can't do any easy TBAA adjustment.  */
+                         operands.release ();
+                         continue;
+                       }
                      else if (alias_set_subset_of (ref->set, set))
                        {
                          ref->set = set;