i386.c (ix86_expand_movmem, [...]): Avoid processing too many bytes on misalligned blocks.

	* i386.c (ix86_expand_movmem, ix86_expand_movstr): Avoid processing too
	many bytes on misalligned blocks.

From-SVN: r140348

gcc/ChangeLog

+2008-09-13  Jan Hubicka  <jh@suse.cz>
+
+	* i386.c (ix86_expand_movmem, ix86_expand_movstr): Avoid processing too
+	many bytes on misalligned blocks.
+
 2008-09-13  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
 
 	* doc/cfg.texi: Fix some typos.

gcc/config/i386/i386.c

@@ -17222,6 +17222,7 @@ ix86_expand_movmem (rtx dst, rtx src, rtx count_exp, rtx align_exp,
   int desired_align = 0;
   enum stringop_alg alg;
   int dynamic_check;
+  bool need_zero_guard = false;
 
   if (CONST_INT_P (align_exp))
     align = INTVAL (align_exp);
@@ -17260,9 +17261,11 @@ ix86_expand_movmem (rtx dst, rtx src, rtx count_exp, rtx align_exp,
     case no_stringop:
       gcc_unreachable ();
     case loop:
+      need_zero_guard = true;
       size_needed = GET_MODE_SIZE (Pmode);
       break;
     case unrolled_loop:
+      need_zero_guard = true;
       size_needed = GET_MODE_SIZE (Pmode) * (TARGET_64BIT ? 4 : 2);
       break;
     case rep_prefix_8_byte:
@@ -17272,7 +17275,10 @@ ix86_expand_movmem (rtx dst, rtx src, rtx count_exp, rtx align_exp,
       size_needed = 4;
       break;
     case rep_prefix_1_byte:
+      size_needed = 1;
+      break;
     case loop_1_byte:
+      need_zero_guard = true;
       size_needed = 1;
       break;
     }
@@ -17350,6 +17356,19 @@ ix86_expand_movmem (rtx dst, rtx src, rtx count_exp, rtx align_exp,
       dst = change_address (dst, BLKmode, destreg);
       expand_movmem_prologue (dst, src, destreg, srcreg, count_exp, align,
 			      desired_align);
+      if (need_zero_guard && !count)
+	{
+	  /* It is possible that we copied enough so the main loop will not
+	     execute.  */
+	  emit_cmp_and_jump_insns (count_exp,
+				   GEN_INT (size_needed),
+				   LTU, 0, counter_mode (count_exp), 1, label);
+	  if (expected_size == -1
+	      || expected_size < (desired_align - align) / 2 + size_needed)
+	    predict_jump (REG_BR_PROB_BASE * 20 / 100);
+	  else
+	    predict_jump (REG_BR_PROB_BASE * 60 / 100);
+	}
     }
   if (label && size_needed == 1)
     {
@@ -17550,6 +17569,7 @@ ix86_expand_setmem (rtx dst, rtx count_exp, rtx val_exp, rtx align_exp,
   rtx promoted_val = NULL;
   bool force_loopy_epilogue = false;
   int dynamic_check;
+  bool need_zero_guard = false;
 
   if (CONST_INT_P (align_exp))
     align = INTVAL (align_exp);
@@ -17587,9 +17607,11 @@ ix86_expand_setmem (rtx dst, rtx count_exp, rtx val_exp, rtx align_exp,
     case no_stringop:
       gcc_unreachable ();
     case loop:
+      need_zero_guard = true;
       size_needed = GET_MODE_SIZE (Pmode);
       break;
     case unrolled_loop:
+      need_zero_guard = true;
       size_needed = GET_MODE_SIZE (Pmode) * 4;
       break;
     case rep_prefix_8_byte:
@@ -17599,7 +17621,10 @@ ix86_expand_setmem (rtx dst, rtx count_exp, rtx val_exp, rtx align_exp,
       size_needed = 4;
       break;
     case rep_prefix_1_byte:
+      size_needed = 1;
+      break;
     case loop_1_byte:
+      need_zero_guard = true;
       size_needed = 1;
       break;
     }
@@ -17675,6 +17700,19 @@ ix86_expand_setmem (rtx dst, rtx count_exp, rtx val_exp, rtx align_exp,
       dst = change_address (dst, BLKmode, destreg);
       expand_setmem_prologue (dst, destreg, promoted_val, count_exp, align,
 			      desired_align);
+      if (need_zero_guard && !count)
+	{
+	  /* It is possible that we copied enough so the main loop will not
+	     execute.  */
+	  emit_cmp_and_jump_insns (count_exp,
+				   GEN_INT (size_needed),
+				   LTU, 0, counter_mode (count_exp), 1, label);
+	  if (expected_size == -1
+	      || expected_size < (desired_align - align) / 2 + size_needed)
+	    predict_jump (REG_BR_PROB_BASE * 20 / 100);
+	  else
+	    predict_jump (REG_BR_PROB_BASE * 60 / 100);
+	}
     }
   if (label && size_needed == 1)
     {