[Bug rtl-optimization/65504] [4.9/5 Regression] select case with strings and -fgcse -O

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65504

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
--- gcc/config/i386/i386.c.jj    2015-03-23 08:47:53.000000000 +0100
+++ gcc/config/i386/i386.c    2015-03-23 13:11:43.416147457 +0100
@@ -23457,12 +23457,19 @@ counter_mode (rtx count_exp)
 static rtx
 ix86_copy_addr_to_reg (rtx addr)
 {
+  rtx reg;
   if (GET_MODE (addr) == Pmode || GET_MODE (addr) == VOIDmode)
-    return copy_addr_to_reg (addr);
+    {
+      reg = copy_addr_to_reg (addr);
+      REG_POINTER (reg) = 1;
+      return reg;
+    }
   else
     {
       gcc_assert (GET_MODE (addr) == DImode && Pmode == SImode);
-      return gen_rtx_SUBREG (SImode, copy_to_mode_reg (DImode, addr), 0);
+      reg = copy_to_mode_reg (DImode, addr);
+      REG_POINTER (reg) = 1;
+      return gen_rtx_SUBREG (SImode, reg, 0);
     }
 }

@@ -24354,6 +24361,8 @@ expand_set_or_movmem_prologue_epilogue_b
       *destptr = expand_simple_binop (GET_MODE (*destptr), PLUS, *destptr,
                       GEN_INT (prolog_size),
                       NULL_RTX, 1, OPTAB_DIRECT);
+      if (REG_P (*destptr) && REG_P (saveddest) && REG_POINTER (*saveddest))
+    REG_POINTER (*destptr) = 1;
       *destptr = expand_simple_binop (GET_MODE (*destptr), AND, *destptr,
                       GEN_INT (-desired_align),
                       *destptr, 1, OPTAB_DIRECT);
@@ -24363,8 +24372,8 @@ expand_set_or_movmem_prologue_epilogue_b
                        saveddest, 1, OPTAB_DIRECT);
       /* Adjust srcptr and count.  */
       if (!issetmem)
-    *srcptr = expand_simple_binop (GET_MODE (*srcptr), MINUS, *srcptr,
saveddest,
-                    *srcptr, 1, OPTAB_DIRECT);
+    *srcptr = expand_simple_binop (GET_MODE (*srcptr), MINUS, *srcptr,
+                       saveddest, *srcptr, 1, OPTAB_DIRECT);
       *count = expand_simple_binop (GET_MODE (*count), PLUS, *count,
                     saveddest, *count, 1, OPTAB_DIRECT);
       /* We copied at most size + prolog_size.  */

fixes this for me.  Without the REG_POINTER flags, aliasing is really confused
on what is a pointer and what is not, as the prologue of the misaligned memcpy
uses
adjusteddest = dest & -align;
src = src - (adjusteddest - dest)
and from these only one has REG_POINTER flag after the propagation, so aliasing
makes a wrong decision from that.