re PR tree-optimization/80492 (Wrong code when unrolling a loop with inline asm and local regs)

2017-04-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80492
	* alias.c (compare_base_decls): Handle registers with asm
	specification conservatively.
	* tree-ssa-alias.c (decl_refs_may_alias_p): Handle
	compare_base_decls returning dont-know properly.

	* gcc.dg/pr80492.c: New testcase.

From-SVN: r247208

gcc/ChangeLog

+2017-04-25  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/80492
+	* alias.c (compare_base_decls): Handle registers with asm
+	specification conservatively.
+	* tree-ssa-alias.c (decl_refs_may_alias_p): Handle
+	compare_base_decls returning dont-know properly.
+
 2017-04-25  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* config/arc/arc.c (LEGITIMATE_OFFSET_ADDRESS_P): Delete macro.

gcc/alias.c

@@ -2046,6 +2046,18 @@ compare_base_decls (tree base1, tree base2)
   if (base1 == base2)
     return 1;
 
+  /* If we have two register decls with register specification we
+     cannot decide unless their assembler name is the same.  */
+  if (DECL_REGISTER (base1)
+      && DECL_REGISTER (base2)
+      && DECL_ASSEMBLER_NAME_SET_P (base1)
+      && DECL_ASSEMBLER_NAME_SET_P (base2))
+    {
+      if (DECL_ASSEMBLER_NAME (base1) == DECL_ASSEMBLER_NAME (base2))
+	return 1;
+      return -1;
+    }
+
   /* Declarations of non-automatic variables may have aliases.  All other
      decls are unique.  */
   if (!decl_in_symtab_p (base1)

gcc/testsuite/ChangeLog

+2017-04-25  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/80492
+	* gcc.dg/pr80492.c: New testcase.
+
 2017-04-25  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
 
 	* gcc.dg/attr-alloc_size-10.c: Ignore overflow warnings

gcc/testsuite/gcc.dg/pr80492.c

+/* { dg-do compile } */
+/* { dg-options "-w -O2 -fdump-tree-optimized" } */
+
+static __inline__ __attribute__((__always_inline__))
+void syscall_7 (int val)
+{
+  register int reg __asm ("4") = val;
+  __asm __volatile__ ("/* Some Code %0 */" :: "r" (reg));
+}
+
+void do_syscalls (void)
+{
+  for (int s = 0; s < 2; s++)
+    {
+      syscall_7 (0);
+      syscall_7 (1);
+    }
+}
+
+/* { dg-final { scan-tree-dump-times "reg = " 4 "optimized" } } */

gcc/tree-ssa-alias.c

@@ -1096,13 +1096,16 @@ decl_refs_may_alias_p (tree ref1, tree base1,
 {
   gcc_checking_assert (DECL_P (base1) && DECL_P (base2));
 
+  int cmp = compare_base_decls (base1, base2);
+
   /* If both references are based on different variables, they cannot alias.  */
-  if (compare_base_decls (base1, base2) == 0)
+  if (cmp == 0)
     return false;
 
   /* If both references are based on the same variable, they cannot alias if
      the accesses do not overlap.  */
-  if (!ranges_overlap_p (offset1, max_size1, offset2, max_size2))
+  if (cmp == 1
+      && !ranges_overlap_p (offset1, max_size1, offset2, max_size2))
     return false;
 
   /* For components with variable position, the above test isn't sufficient,