From 7280c2a4f0ece9a4b2876d52a683e0b92af1b10d Mon Sep 17 00:00:00 2001
From: Richard Kenner <kenner@gcc.gnu.org>
Date: Thu, 11 Aug 1994 13:13:20 -0400
Subject: [PATCH] (find_auto_inc): Ensure that all proposed changes to insns
 are valid before commiting to the auto-inc.

From-SVN: r7889
---
 gcc/flow.c | 98 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 55 insertions(+), 43 deletions(-)

diff --git a/gcc/flow.c b/gcc/flow.c
index db4f37f64e3..56c5ca737e1 100644
--- a/gcc/flow.c
+++ b/gcc/flow.c
@@ -2090,11 +2090,21 @@ find_auto_inc (needed, x, insn)
 	  && (use = find_use_as_address (PATTERN (insn), addr, offset),
 	      use != 0 && use != (rtx) 1))
 	{
-	  int win = 0;
 	  rtx q = SET_DEST (set);
+	  enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
+				    ? (offset ? PRE_INC : POST_INC)
+				    : (offset ? PRE_DEC : POST_DEC));
 
 	  if (dead_or_set_p (incr, addr))
-	    win = 1;
+	    {
+	      /* This is the simple case.  Try to make the auto-inc.  If
+		 we can't, we are done.  Otherwise, we will do any
+		 needed updates below.  */
+	      if (! validate_change (insn, &XEXP (x, 0),
+				     gen_rtx (inc_code, Pmode, addr),
+				     0))
+		return;
+	    }
 	  else if (GET_CODE (q) == REG
 		   /* PREV_INSN used here to check the semi-open interval
 		      [insn,incr).  */
@@ -2122,14 +2132,25 @@ find_auto_inc (needed, x, insn)
 		  BLOCK_NUM (temp) = BLOCK_NUM (insn);
 		}
 
+	      /* If we can't make the auto-inc, or can't make the
+		 replacement into Y, exit.  There's no point in making
+		 the change below if we can't do the auto-inc and doing
+		 so is not correct in the pre-inc case.  */
+
+	      validate_change (insn, &XEXP (x, 0),
+			       gen_rtx (inc_code, Pmode, q),
+			       1);
+	      validate_change (incr, &XEXP (y, 0), q, 1);
+	      if (! apply_change_group ())
+		return;
+
+	      /* We now know we'll be doing this change, so emit the
+		 new insn(s) and do the updates.  */
 	      emit_insns_before (insns, insn);
 
 	      if (basic_block_head[BLOCK_NUM (insn)] == insn)
 		basic_block_head[BLOCK_NUM (insn)] = insns;
 
-	      XEXP (x, 0) = q;
-	      XEXP (y, 0) = q;
-
 	      /* INCR will become a NOTE and INSN won't contain a
 		 use of ADDR.  If a use of ADDR was just placed in
 		 the insn before INSN, make that the next use. 
@@ -2143,7 +2164,6 @@ find_auto_inc (needed, x, insn)
 
 	      addr = q;
 	      regno = REGNO (q);
-	      win = 1;
 
 	      /* REGNO is now used in INCR which is below INSN, but
 		 it previously wasn't live here.  If we don't mark
@@ -2159,46 +2179,38 @@ find_auto_inc (needed, x, insn)
 		  reg_n_calls_crossed[regno]++;
 	    }
 
-	  if (win
-	      /* If we have found a suitable auto-increment, do
-		 POST_INC around the register here, and patch out the
-		 increment instruction that follows. */
-	      && validate_change (insn, &XEXP (x, 0),
-				  gen_rtx ((INTVAL (XEXP (y, 1)) == size
-					    ? (offset ? PRE_INC : POST_INC)
-					    : (offset ? PRE_DEC : POST_DEC)),
-					   Pmode, addr), 0))
+	  /* If we haven't returned, it means we were able to make the
+	     auto-inc, so update the status.  First, record that this insn
+	     has an implicit side effect.  */
+
+	  REG_NOTES (insn)
+	    = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
+
+	  /* Modify the old increment-insn to simply copy
+	     the already-incremented value of our register.  */
+	  if (! validate_change (incr, &SET_SRC (set), addr, 0))
+	    abort ();
+
+	  /* If that makes it a no-op (copying the register into itself) delete
+	     it so it won't appear to be a "use" and a "set" of this
+	     register.  */
+	  if (SET_DEST (set) == addr)
 	    {
-	      /* Record that this insn has an implicit side effect.  */
-	      REG_NOTES (insn)
-		= gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
+	      PUT_CODE (incr, NOTE);
+	      NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
+	      NOTE_SOURCE_FILE (incr) = 0;
+	    }
 
-	      /* Modify the old increment-insn to simply copy
-		 the already-incremented value of our register.  */
-	      SET_SRC (set) = addr;
-	      /* Indicate insn must be re-recognized.  */
-	      INSN_CODE (incr) = -1;
+	  if (regno >= FIRST_PSEUDO_REGISTER)
+	    {
+	      /* Count an extra reference to the reg.  When a reg is
+		 incremented, spilling it is worse, so we want to make
+		 that less likely.  */
+	      reg_n_refs[regno] += loop_depth;
 
-	      /* If that makes it a no-op (copying the register into itself)
-		 then delete it so it won't appear to be a "use" and a "set"
-		 of this register.  */
-	      if (SET_DEST (set) == addr)
-		{
-		  PUT_CODE (incr, NOTE);
-		  NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
-		  NOTE_SOURCE_FILE (incr) = 0;
-		}
-
-	      if (regno >= FIRST_PSEUDO_REGISTER)
-		{
-		  /* Count an extra reference to the reg.  When a reg is
-		     incremented, spilling it is worse, so we want to make
-		     that less likely.  */
-		  reg_n_refs[regno] += loop_depth;
-		  /* Count the increment as a setting of the register,
-		     even though it isn't a SET in rtl.  */
-		  reg_n_sets[regno]++;
-		}
+	      /* Count the increment as a setting of the register,
+		 even though it isn't a SET in rtl.  */
+	      reg_n_sets[regno]++;
 	    }
 	}
     }