[patch] Disable store merging in asan_expand_mark_ifn

[Eric Botcazou]

Hi,

asan_expand_mark_ifn does manual store merging but doesn't take into account 
the alignment, so this can break on strict-alignment platforms.

Tested on SPARC/Solaris 11, where this fixes this regression:

FAIL: gcc.dg/asan/use-after-scope-5.c   -O0  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O1  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O2  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O3 -fomit-frame-pointer -funroll-
loops -fpeel-loops -ftracer -finline-functions  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O3 -g  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -Os  output pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O2 -flto -flto-partition=none  output 
pattern test
FAIL: gcc.dg/asan/use-after-scope-5.c   -O2 -flto  output pattern test

OK for mainline?


2019-02-11  Eric Botcazou  <ebotca...@adacore.com>

        * asan.c (asan_expand_mark_ifn): Always use a size of 1 byte for the
        stores on strict-alignment platforms.

-- 
Eric Botcazou
Index: asan.c
===================================================================
--- asan.c	(revision 268508)
+++ asan.c	(working copy)
@@ -3226,10 +3226,13 @@ asan_expand_mark_ifn (gimple_stmt_iterat
       for (unsigned HOST_WIDE_INT offset = 0; offset < shadow_size;)
 	{
 	  unsigned size = 1;
-	  if (shadow_size - offset >= 4)
-	    size = 4;
-	  else if (shadow_size - offset >= 2)
-	    size = 2;
+	  if (!STRICT_ALIGNMENT)
+	    {
+	      if (shadow_size - offset >= 4)
+		size = 4;
+	      else if (shadow_size - offset >= 2)
+		size = 2;
+	    }
 
 	  unsigned HOST_WIDE_INT last_chunk_size = 0;
 	  unsigned HOST_WIDE_INT s = (offset + size) * ASAN_SHADOW_GRANULARITY;