Re: [patch] Disable store merging in asan_expand_mark_ifn

[Eric Botcazou]

> > OK, revised patch attached.  I have manually verified that it yields the
> > expected result for an array of long doubles on 64-bit SPARC.
> > 
> > 
> > 2019-02-12  Eric Botcazou  <ebotca...@adacore.com>
> > 
> >     * asan.c (asan_expand_mark_ifn): Take into account the alignment of
> >     the object to pick the size of stores on strict-alignment platforms.
> 
> Ok, thanks.

Glad you insisted in the end, because I have ASAN working on SPARC64/Linux, 
but only after fixing another bug on 64-bit strict-alignment platforms:

  /* Align base if target is STRICT_ALIGNMENT.  */
  if (STRICT_ALIGNMENT)
    base = expand_binop (Pmode, and_optab, base,
                         gen_int_mode (-((GET_MODE_ALIGNMENT (SImode)
                                          << ASAN_SHADOW_SHIFT)
                                         / BITS_PER_UNIT), Pmode), NULL_RTX,
                         1, OPTAB_DIRECT);

GET_MODE_ALIGNMENT is unsigned int so this zero-extends to unsigned long...

Tested on 32-bit and 64-bit SPARC/Linux, applied on mainline as obvious.


2019-02-15  Eric Botcazou  <ebotca...@adacore.com>

        * asan.c (asan_emit_stack_protection): Use full-sized mask to align
        the base address on 64-bit strict-alignment platforms.

-- 
Eric Botcazou
Index: asan.c
===================================================================
--- asan.c	(revision 268849)
+++ asan.c	(working copy)
@@ -1440,13 +1441,15 @@ asan_emit_stack_protection (rtx base, rt
 	base_align_bias = ((asan_frame_size + alignb - 1)
 			   & ~(alignb - HOST_WIDE_INT_1)) - asan_frame_size;
     }
+
   /* Align base if target is STRICT_ALIGNMENT.  */
   if (STRICT_ALIGNMENT)
-    base = expand_binop (Pmode, and_optab, base,
-			 gen_int_mode (-((GET_MODE_ALIGNMENT (SImode)
-					  << ASAN_SHADOW_SHIFT)
-					 / BITS_PER_UNIT), Pmode), NULL_RTX,
-			 1, OPTAB_DIRECT);
+    {
+      const HOST_WIDE_INT align
+	= (GET_MODE_ALIGNMENT (SImode) / BITS_PER_UNIT) << ASAN_SHADOW_SHIFT;
+      base = expand_binop (Pmode, and_optab, base, gen_int_mode (-align, Pmode),
+			   NULL_RTX, 1, OPTAB_DIRECT);
+    }
 
   if (use_after_return_class == -1 && pbase)
     emit_move_insn (pbase, base);
@ -1534,7 +1548,7 @@ asan_emit_stack_protection (rtx base, rt
   shadow_mem = gen_rtx_MEM (SImode, shadow_base);
   set_mem_alias_set (shadow_mem, asan_shadow_set);
   if (STRICT_ALIGNMENT)
-    set_mem_align (shadow_mem, (GET_MODE_ALIGNMENT (SImode)));
+    set_mem_align (shadow_mem, GET_MODE_ALIGNMENT (SImode));
   prev_offset = base_offset;
 
   asan_redzone_buffer rz_buffer (shadow_mem, prev_offset);