re PR target/79430 (action of statement incorrectly optimised away)

	PR target/79430
	* rtlanal.c (reg_set_p): If reg is a stack_pointer_rtx, also
	check for stack push/pop autoinc.
	* config/i386/i386.c (ix86_agi_dependent): Return false
	if the only reason why modified_in_p returned true is that
	addr is SP based and set_insn is a push or pop.

From-SVN: r247429

gcc/ChangeLog

+2017-05-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/79430
+	* rtlanal.c (reg_set_p): If reg is a stack_pointer_rtx, also
+	check for stack push/pop autoinc.
+	* config/i386/i386.c (ix86_agi_dependent): Return false
+	if the only reason why modified_in_p returned true is that
+	addr is SP based and set_insn is a push or pop.
+
 2017-04-29  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR ipa/79224

gcc/config/i386/i386.c

@@ -29243,7 +29243,26 @@ ix86_agi_dependent (rtx_insn *set_insn, rtx_insn *use_insn)
     if (MEM_P (recog_data.operand[i]))
       {
 	rtx addr = XEXP (recog_data.operand[i], 0);
-	return modified_in_p (addr, set_insn) != 0;
+	if (modified_in_p (addr, set_insn) != 0)
+	  {
+	    /* No AGI stall if SET_INSN is a push or pop and USE_INSN
+	       has SP based memory (unless index reg is modified in a pop).  */
+	    rtx set = single_set (set_insn);
+	    if (set
+		&& (push_operand (SET_DEST (set), GET_MODE (SET_DEST (set)))
+		    || pop_operand (SET_SRC (set), GET_MODE (SET_SRC (set)))))
+	      {
+		struct ix86_address parts;
+		if (ix86_decompose_address (addr, &parts)
+		    && parts.base == stack_pointer_rtx
+		    && (parts.index == NULL_RTX
+			|| MEM_P (SET_DEST (set))
+			|| !modified_in_p (parts.index, set_insn)))
+		  return false;
+	      }
+	    return true;
+	  }
+	return false;
       }
   return false;
 }

gcc/rtlanal.c

@@ -1221,6 +1221,24 @@ reg_set_p (const_rtx reg, const_rtx insn)
 		  || find_reg_fusage (insn, CLOBBER, reg)))))
     return true;
 
+  /* There are no REG_INC notes for SP autoinc.  */
+  if (reg == stack_pointer_rtx && INSN_P (insn))
+    {
+      subrtx_var_iterator::array_type array;
+      FOR_EACH_SUBRTX_VAR (iter, array, PATTERN (insn), NONCONST)
+	{
+	  rtx mem = *iter;
+	  if (mem
+	      && MEM_P (mem)
+	      && GET_RTX_CLASS (GET_CODE (XEXP (mem, 0))) == RTX_AUTOINC)
+	    {
+	      if (XEXP (XEXP (mem, 0), 0) == stack_pointer_rtx)
+		return true;
+	      iter.skip_subrtxes ();
+	    }
+	}
+    }
+
   return set_of (reg, insn) != NULL_RTX;
 }