[Bug target/30778] [4.3 Regression] invalid code generation for memset() with -mtune=k8

["hubicka at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #6 from hubicka at gcc dot gnu dot org  2007-02-24 23:47 -------
Hi,
this is version I ended up with.  In general I don't think that code should
handle with such a small constant sizes, we probably should bump move_by_pieces
constants since it can do better job using proper moves not triggering partial
memory stalls.

This patch however fixes one extra pasto and makes the prologue test
unconditional - I was a bit overagressive minimizing amount of RTL produced
that only leads to bugs in side corners.

Thanks a lot for looking into it - I should've dealt with this bug a lot
sooner, but I was very busy last week...
Honza

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c  (revision 122292)
+++ config/i386/i386.c  (working copy)
@@ -13522,7 +13522,7 @@ expand_movmem_epilogue (rtx destmem, rtx
       HOST_WIDE_INT countval = INTVAL (count);
       int offset = 0;

-      if ((countval & 0x16) && max_size > 16)
+      if ((countval & 0x10) && max_size > 16)
        {
          if (TARGET_64BIT)
            {
@@ -13539,8 +13539,8 @@ expand_movmem_epilogue (rtx destmem, rtx
            emit_strmov (destmem, srcmem, destptr, srcptr, DImode, offset);
          else
            {
-             emit_strmov (destmem, srcmem, destptr, srcptr, DImode, offset);
-             emit_strmov (destmem, srcmem, destptr, srcptr, DImode, offset +
4);
+             emit_strmov (destmem, srcmem, destptr, srcptr, SImode, offset);
+             emit_strmov (destmem, srcmem, destptr, srcptr, SImode, offset +
4);
            }
          offset += 8;
        }
@@ -13675,7 +13675,7 @@ expand_setmem_epilogue (rtx destmem, rtx
       HOST_WIDE_INT countval = INTVAL (count);
       int offset = 0;

-      if ((countval & 0x16) && max_size > 16)
+      if ((countval & 0x10) && max_size > 16)
        {
          if (TARGET_64BIT)
            {
@@ -14118,19 +14118,22 @@ ix86_expand_movmem (rtx dst, rtx src, rt
   gcc_assert (desired_align >= 1 && align >= 1);

   /* Ensure that alignment prologue won't copy past end of block.  */
-  if ((size_needed > 1 || (desired_align > 1 && desired_align > align))
-      && !count)
+  if (size_needed > 1 || (desired_align > 1 && desired_align > align))
     {
-      epilogue_size_needed = MAX (size_needed - 1, desired_align - align);
+      enum machine_mode mode = GET_MODE (count_exp);

+      if (mode == VOIDmode)
+       mode = DImode; 
+
+      epilogue_size_needed = MAX (size_needed - 1, desired_align - align);
       /* Epilogue always copies COUNT_EXP & EPILOGUE_SIZE_NEEDED bytes.
         Make sure it is power of 2.  */
       epilogue_size_needed = smallest_pow2_greater_than
(epilogue_size_needed);

       label = gen_label_rtx ();
-      emit_cmp_and_jump_insns (count_exp,
+      emit_cmp_and_jump_insns (force_reg (mode, count_exp),
                               GEN_INT (epilogue_size_needed),
-                              LTU, 0, GET_MODE (count_exp), 1, label);
+                              LTU, 0, mode, 1, label);
       if (expected_size == -1 || expected_size < epilogue_size_needed)
        predict_jump (REG_BR_PROB_BASE * 60 / 100);
       else
@@ -14430,11 +14433,14 @@ ix86_expand_setmem (rtx dst, rtx count_e
     promoted_val = promote_duplicated_reg_to_size (val_exp, size_needed,
                                                   desired_align, align);
   /* Ensure that alignment prologue won't copy past end of block.  */
-  if ((size_needed > 1 || (desired_align > 1 && desired_align > align))
-      && !count)
+  if (size_needed > 1 || (desired_align > 1 && desired_align > align))
     {
-      epilogue_size_needed = MAX (size_needed - 1, desired_align - align);
+      enum machine_mode mode = GET_MODE (count_exp);
+
+      if (mode == VOIDmode)
+       mode = DImode; 

+      epilogue_size_needed = MAX (size_needed - 1, desired_align - align);
       /* Epilogue always copies COUNT_EXP & EPILOGUE_SIZE_NEEDED bytes.
         Make sure it is power of 2.  */
       epilogue_size_needed = smallest_pow2_greater_than
(epilogue_size_needed);
@@ -14446,9 +14452,9 @@ ix86_expand_setmem (rtx dst, rtx count_e
       if (epilogue_size_needed > 2 && !promoted_val)
         force_loopy_epilogue = true;
       label = gen_label_rtx ();
-      emit_cmp_and_jump_insns (count_exp,
+      emit_cmp_and_jump_insns (force_reg (mode, count_exp),
                               GEN_INT (epilogue_size_needed),
-                              LTU, 0, GET_MODE (count_exp), 1, label);
+                              LTU, 0, mode, 1, label);
       if (expected_size == -1 || expected_size <= epilogue_size_needed)
        predict_jump (REG_BR_PROB_BASE * 60 / 100);
       else


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30778