Fix LRA bug

This patch fixes an ICE building libgfortran/random.c.

The problem was an adddi3 instruction that had an eliminable frame pointer.
GCN adddi3 includes a match_scratch, which LRA substitutes with a REG, and
checks if it can be converted back to a scratch afterwards.  In the meantime,
the add was converted to a move, meaning that the instruction pattern
completely changed, thus causing a segfault when the instruction is revisited
in restore_scratches.

2018-12-14  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* gcc/lra-int.h (lra_register_new_scratch_op): Add third parameter.
	* gcc/lra-remat.c (update_scratch_ops): Pass icode to
	lra_register_new_scratch_op.
	* gcc/lra.c (struct sloc): Add icode field.
	(lra_register_new_scratch_op): Add icode parameter.
	Use icode to skip insns that have changed beyond recognition.

From-SVN: r267132

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2018-12-14  Andrew Stubbs  <ams@codesourcery.com>
+
+	* gcc/lra-int.h (lra_register_new_scratch_op): Add third parameter.
+	* gcc/lra-remat.c (update_scratch_ops): Pass icode to
+	lra_register_new_scratch_op.
+	* gcc/lra.c (struct sloc): Add icode field.
+	(lra_register_new_scratch_op): Add icode parameter.
+	Use icode to skip insns that have changed beyond recognition.
+
 2018-12-14  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* dwarf2out.c (analyze_discr_in_predicate): Simplify.

gcc/lra-int.h

@@ -336,7 +336,7 @@ extern void lra_create_copy (int, int, int);
 extern lra_copy_t lra_get_copy (int);
 extern bool lra_former_scratch_p (int);
 extern bool lra_former_scratch_operand_p (rtx_insn *, int);
-extern void lra_register_new_scratch_op (rtx_insn *, int);
+extern void lra_register_new_scratch_op (rtx_insn *, int, int);
 
 extern int lra_new_regno_start;
 extern int lra_constraint_new_regno_start;

gcc/lra-remat.c

@@ -1042,7 +1042,7 @@ update_scratch_ops (rtx_insn *remat_insn)
 	    fprintf (lra_dump_file, "	 Assigning the same %d to r%d\n",
 		     REGNO (*loc), hard_regno);
 	}
-      lra_register_new_scratch_op (remat_insn, i);
+      lra_register_new_scratch_op (remat_insn, i, id->icode);
     }
   
 }

gcc/lra.c

@@ -2026,6 +2026,7 @@ struct sloc
 {
   rtx_insn *insn; /* Insn where the scratch was.  */
   int nop;  /* Number of the operand which was a scratch.  */
+  int icode;  /* Original icode from which scratch was removed.  */
 };
 
 typedef struct sloc *sloc_t;
@@ -2057,7 +2058,7 @@ lra_former_scratch_operand_p (rtx_insn *insn, int nop)
 /* Register operand NOP in INSN as a former scratch.  It will be
    changed to scratch back, if it is necessary, at the LRA end.  */
 void
-lra_register_new_scratch_op (rtx_insn *insn, int nop)
+lra_register_new_scratch_op (rtx_insn *insn, int nop, int icode)
 {
   lra_insn_recog_data_t id = lra_get_insn_recog_data (insn);
   rtx op = *id->operand_loc[nop];
@@ -2065,6 +2066,7 @@ lra_register_new_scratch_op (rtx_insn *insn, int nop)
   lra_assert (REG_P (op));
   loc->insn = insn;
   loc->nop = nop;
+  loc->icode = icode;
   scratches.safe_push (loc);
   bitmap_set_bit (&scratch_bitmap, REGNO (op));
   bitmap_set_bit (&scratch_operand_bitmap,
@@ -2102,7 +2104,7 @@ remove_scratches (void)
 	      *id->operand_loc[i] = reg
 		= lra_create_new_reg (static_id->operand[i].mode,
 				      *id->operand_loc[i], ALL_REGS, NULL);
-	      lra_register_new_scratch_op (insn, i);
+	      lra_register_new_scratch_op (insn, i, id->icode);
 	      if (lra_dump_file != NULL)
 		fprintf (lra_dump_file,
 			 "Removing SCRATCH in insn #%u (nop %d)\n",
@@ -2136,6 +2138,12 @@ restore_scratches (void)
 	  last = loc->insn;
 	  id = lra_get_insn_recog_data (last);
 	}
+      if (loc->icode != id->icode)
+	{
+	  /* The icode doesn't match, which means the insn has been modified
+	     (e.g. register elimination).  The scratch cannot be restored.  */
+	  continue;
+	}
       if (REG_P (*id->operand_loc[loc->nop])
 	  && ((regno = REGNO (*id->operand_loc[loc->nop]))
 	      >= FIRST_PSEUDO_REGISTER)