df-scan: remove ad-hoc handling of global regs in asms

	PR rtl-optimization/79985
	* df-scan.c (df_insn_refs_collect): Remove special case for
	global registers and asm statements.

testsuite/
	* gcc.dg/pr79985.c: New testcase.

From-SVN: r260613

gcc/ChangeLog

 2018-05-23  Alexander Monakov  <amonakov@ispras.ru>
 
+	PR rtl-optimization/79985
+	* df-scan.c (df_insn_refs_collect): Remove special case for
+	global registers and asm statements.
+
+2018-05-23  Alexander Monakov  <amonakov@ispras.ru>
+
 	* extend.texi (Global Register Variables): Rewrite the bullet list.
 	Note that the register is available for allocation. Note that access
 	via inline asm must use constraints. Add note about async-signal

gcc/df-scan.c

@@ -3207,17 +3207,6 @@ df_insn_refs_collect (struct df_collection_rec *collection_rec,
   if (CALL_P (insn_info->insn))
     df_get_call_refs (collection_rec, bb, insn_info, flags);
 
-  if (asm_noperands (PATTERN (insn_info->insn)) >= 0)
-    for (unsigned i = 0; i < FIRST_PSEUDO_REGISTER; i++)
-      if (global_regs[i])
-       {
-         /* As with calls, asm statements reference all global regs. */
-         df_ref_record (DF_REF_BASE, collection_rec, regno_reg_rtx[i],
-                        NULL, bb, insn_info, DF_REF_REG_USE, flags);
-         df_ref_record (DF_REF_BASE, collection_rec, regno_reg_rtx[i],
-                        NULL, bb, insn_info, DF_REF_REG_DEF, flags);
-       }
-
   /* Record other defs.  These should be mostly for DF_REF_REGULAR, so
      that a qsort on the defs is unnecessary in most cases.  */
   df_defs_record (collection_rec,

gcc/testsuite/ChangeLog

+2018-05-23  Alexander Monakov  <amonakov@ispras.ru>
+
+	* gcc.dg/pr79985.c: New testcase.
+
 2018-05-23  Richard Biener  <rguenther@suse.de>
 
 	* gcc.dg/tree-ssa/ssa-fre-66.c: New testcase.

gcc/testsuite/gcc.dg/pr79985.c

+/* PR rtl-optimization/79985 */
+/* { dg-do compile { target powerpc*-*-* ia64-*-* i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O3 -fschedule-insns -fselective-scheduling" } */
+
+long a;
+int b;
+void
+c ()
+{
+  __asm("" : "=r"(a) : "0"(c));
+  __asm("" : "=r"(b));
+}