From 9ef4c6ef3c6a37f382303c6fc4f9bea1b7e85e28 Mon Sep 17 00:00:00 2001
From: John Carr <jfc@gcc.gnu.org>
Date: Sun, 6 Sep 1998 05:52:01 +0000
Subject: [PATCH] final.c (final): If a label is reached only from a single
 jump...

d
	* final.c (final): If a label is reached only from a single jump,
	call NOTICE_UPDATE_CC on the jump and its predecessor before
	emitting the insn after the label.
	* i386.h: Add AMD K6 support.
	Change TARGET_* macros to use table lookup.
	(INITIALIZE_TRAMPOLINE): Improve trampoline code.
	(ADJUST_COST): Change definition to call function in i386.c.
	(ISSUE_RATE): Define as 2 for anything newer than an 80486.
	* i386.c: Add AMD K6 support.
	Add constants for feature tests used by TARGET_* macros.
	(split_di): If before reload, call gen_lowpart and gen_highpart.
	(x86_adjust_cost): New function.
	(put_jump_code): New function.
	(print_operand): New codes 'D' and 'd'.
	* i386.md: New insn types.  New insn attribute "memory".
	Redefine scheduling parameters to use new types and add AMD K6
	support.  Explicitly set type of most insns.
	(move insns): K6 prefers movl $0,reg to xorl reg,reg.  Pentium
	Pro and K6 prefer movl $1,reg to incl reg.
	(adddi3, subdi3): Set cc_status.
	(DImode shift patterns): Change label counters from HOST_WIDE_INT
	to int; x86 can't have more than 2^31 DImode shifts per	file.
	(setcc): Combine all setcc patterns.  Allow writing memory.
	Combine all jump patterns using match_operator.
	(*bzero): Name pattern.  Emit mutliple stos instructions when that
	is faster than rep stos.
	(xordi3, anddi3, iordi3): Simplify DImode logical patterns and
	add define_split.
	* ch/Make-lang.in: Comment ^L characters.  Sun make doesn't like them.

From-SVN: r22290
---
 gcc/final.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/gcc/final.c b/gcc/final.c
index 0938e221d5e..454ab6c71f5 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -1980,6 +1980,18 @@ final (first, file, optimize, prescan)
         max_uid = INSN_UID (insn);
       if (GET_CODE (insn) == NOTE && NOTE_LINE_NUMBER (insn) > 0)
         line_note_exists[NOTE_LINE_NUMBER (insn)] = 1;
+#ifdef HAVE_cc0
+      /* If CC tracking across branches is enabled, record the insn which
+	 jumps to each branch only reached from one place.  */
+      if (GET_CODE (insn) == JUMP_INSN)
+	{
+	  rtx lab = JUMP_LABEL (insn);
+	  if (lab && LABEL_NUSES (lab) == 1)
+	    {
+	      LABEL_REFS (lab) = insn;
+	    }
+	}
+#endif
     }
 
   /* Initialize insn_eh_region table if eh is being used. */
@@ -2283,7 +2295,30 @@ final_scan_insn (insn, file, optimize, prescan, nopeepholes)
 	    ASM_OUTPUT_ALIGN (file, align);
 #endif
 	}
+#ifdef HAVE_cc0
       CC_STATUS_INIT;
+      /* If this label is reached from only one place, set the condition
+	 codes from the instruction just before the branch.  */
+      if (LABEL_NUSES (insn) == 1)
+	{
+	  rtx jump = LABEL_REFS (insn);
+	  rtx barrier = prev_nonnote_insn (insn);
+	  rtx prev;
+	  /* If the LABEL_REFS field of this label has been set to point
+	     at a branch, the predecessor of the branch is a regular
+	     insn, and that branch is the only way to reach this label,
+	     set the condition codes based on the branch and its
+	     predecessor.  */
+	  if (barrier && GET_CODE (barrier) == BARRIER
+	      && jump && GET_CODE (jump) == JUMP_INSN
+	      && (prev = prev_nonnote_insn (jump))
+	      && GET_CODE (prev) == INSN)
+	    {
+	      NOTICE_UPDATE_CC (PATTERN (prev), prev);
+	      NOTICE_UPDATE_CC (PATTERN (jump), jump);
+	    }
+	}
+#endif
       if (prescan > 0)
 	break;
       new_block = 1;
-- 
2.30.2