re PR tree-optimization/52571 (vectorizer changes alignment of common symbols)

2012-03-14  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/52571
	* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Move
	flag_section_anchors check ...
	(vect_can_force_dr_alignment_p): ... here.  Do not re-align
	DECL_COMMON variables.

	* gcc.dg/vect/vect-2.c: Initialize arrays.
	* gcc.dg/vect/no-section-anchors-vect-34.c: Likewise.
	* gcc.target/i386/recip-vec-divf.c: Use -fno-common.
	* gcc.target/i386/recip-vec-sqrtf.c: Likewise.

From-SVN: r185380

gcc/ChangeLog

 2012-03-14  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/52571
+	* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Move
+	flag_section_anchors check ...
+	(vect_can_force_dr_alignment_p): ... here.  Do not re-align
+	DECL_COMMON variables.
+
+2012-03-14  Richard Guenther  <rguenther@suse.de>
+
 	* tree.h (DECL_BIT_FIELD_REPRESENTATIVE): New define.
 	* stor-layout.c (start_bitfield_representative): New function.
 	(finish_bitfield_representative): Likewise.

gcc/testsuite/ChangeLog

 2012-03-14  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/52571
+	* gcc.dg/vect/vect-2.c: Initialize arrays.
+	* gcc.dg/vect/no-section-anchors-vect-34.c: Likewise.
+	* gcc.target/i386/recip-vec-divf.c: Use -fno-common.
+	* gcc.target/i386/recip-vec-sqrtf.c: Likewise.
+
+2012-03-14  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/52080
 	PR middle-end/52097
 	PR middle-end/48124

gcc/testsuite/gcc.dg/vect/no-section-anchors-vect-34.c

@@ -7,7 +7,7 @@
  
 struct {
   char ca[N];
-} s;
+} s = {};
 char cb[N] = {0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45};
 
 __attribute__ ((noinline))

gcc/testsuite/gcc.dg/vect/vect-2.c

@@ -6,7 +6,7 @@
 #define N 16
 
 char cb[N] = {0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45};
-char ca[N];
+char ca[N] = {};
 
 __attribute__ ((noinline)) 
 int main1 ()

gcc/testsuite/gcc.target/i386/recip-vec-divf.c

 /* { dg-do compile } */
-/* { dg-options "-O2 -ffast-math -ftree-vectorize -msse -mfpmath=sse -mrecip" } */
+/* { dg-options "-O2 -ffast-math -ftree-vectorize -msse -mfpmath=sse -mrecip -fno-common" } */
 
 float a[4];
 float b[4];

gcc/testsuite/gcc.target/i386/recip-vec-sqrtf.c

 /* { dg-do compile } */
-/* { dg-options "-O2 -ffast-math -ftree-vectorize -msse -mfpmath=sse -mrecip" } */
+/* { dg-options "-O2 -ffast-math -ftree-vectorize -msse -mfpmath=sse -mrecip -fno-common" } */
 
 float a[4];
 float b[4];

gcc/tree-vect-data-refs.c

@@ -872,10 +872,7 @@ vect_compute_data_ref_alignment (struct data_reference *dr)
 
   if (!base_aligned)
     {
-      /* Do not change the alignment of global variables if
-	 flag_section_anchors is enabled.  */
-      if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype))
-	  || (TREE_STATIC (base) && flag_section_anchors))
+      if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype)))
 	{
 	  if (vect_print_dump_info (REPORT_DETAILS))
 	    {
@@ -4546,12 +4543,22 @@ vect_can_force_dr_alignment_p (const_tree decl, unsigned int alignment)
   if (TREE_CODE (decl) != VAR_DECL)
     return false;
 
-  if (DECL_EXTERNAL (decl))
+  /* We cannot change alignment of common or external symbols as another
+     translation unit may contain a definition with lower alignment.  
+     The rules of common symbol linking mean that the definition
+     will override the common symbol.  */
+  if (DECL_EXTERNAL (decl)
+      || DECL_COMMON (decl))
     return false;
 
   if (TREE_ASM_WRITTEN (decl))
     return false;
 
+  /* Do not change the alignment of global variables if flag_section_anchors
+     is enabled.  */
+  if (TREE_STATIC (decl) && flag_section_anchors)
+    return false;
+
   if (TREE_STATIC (decl))
     return (alignment <= MAX_OFILE_ALIGNMENT);
   else