[gcc r10-10260] tree-optimization/100253 - fix bogus aligned vectorized loads/stores

[gcc r10-10260] tree-optimization/100253 - fix bogus aligned vectorized loads/stores

[Richard Biener]

https://gcc.gnu.org/g:92ffe7c3b6ffee8fd6ef92a5b3b4cc09263b01ee

commit r10-10260-g92ffe7c3b6ffee8fd6ef92a5b3b4cc09263b01ee
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Apr 29 11:52:08 2021 +0200

    tree-optimization/100253 - fix bogus aligned vectorized loads/stores
    
    At some point DR_MISALIGNMENT was supposed to be -1 when the
    access was not element aligned.  That's obviously not true at this
    point so this adjusts both store and load vectorizing to no longer
    assume this which in turn allows simplifying the code.
    
    2021-04-29  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/100253
            * tree-vect-stmts.c (vectorizable_load): Do not assume
            element alignment when DR_MISALIGNMENT is -1.
            (vectorizable_store): Likewise.
    
            * g++.dg/pr100253.C: New testcase.

Diff:
---
 gcc/testsuite/g++.dg/pr100253.C | 33 +++++++++++++++++++++++++++++++++
 gcc/tree-vect-stmts.c           | 16 ++++------------
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/gcc/testsuite/g++.dg/pr100253.C b/gcc/testsuite/g++.dg/pr100253.C
new file mode 100644
index 00000000000..0102caa7df8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr100253.C
@@ -0,0 +1,33 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-tree-bit-ccp -ftree-slp-vectorize" } */
+
+#include <vector>
+
+struct T
+{
+};
+
+struct S
+{
+  std::vector < std::vector < T > > v;
+  char x;
+  char y[16];
+  char z[16];
+};
+
+S s, g[1];
+
+void
+foo (char *buf)
+{
+  s = g[*buf];
+}
+
+char c;
+
+int
+main ()
+{
+  foo (&c);
+  return 0;
+}
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 6418edb5204..2ef71ec41c0 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -8368,6 +8368,7 @@ vectorizable_store (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 		  && TREE_CODE (dataref_ptr) == SSA_NAME)
 		set_ptr_info_alignment (get_ptr_info (dataref_ptr), align,
 					misalign);
+	      align = least_bit_hwi (misalign | align);
 
 	      if (memory_access_type == VMAT_CONTIGUOUS_REVERSE)
 		{
@@ -8389,7 +8390,6 @@ vectorizable_store (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 	      /* Arguments are ready.  Create the new vector stmt.  */
 	      if (final_mask)
 		{
-		  align = least_bit_hwi (misalign | align);
 		  tree ptr = build_int_cst (ref_type, align * BITS_PER_UNIT);
 		  gcall *call
 		    = gimple_build_call_internal (IFN_MASK_STORE, 4,
@@ -8408,14 +8408,10 @@ vectorizable_store (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 					  : build_int_cst (ref_type, 0));
 		  if (aligned_access_p (first_dr_info))
 		    ;
-		  else if (DR_MISALIGNMENT (first_dr_info) == -1)
-		    TREE_TYPE (data_ref)
-		      = build_aligned_type (TREE_TYPE (data_ref),
-					    align * BITS_PER_UNIT);
 		  else
 		    TREE_TYPE (data_ref)
 		      = build_aligned_type (TREE_TYPE (data_ref),
-					    TYPE_ALIGN (elem_type));
+					    align * BITS_PER_UNIT);
 		  vect_copy_ref_info (data_ref, DR_REF (first_dr_info->dr));
 		  gassign *new_stmt
 		    = gimple_build_assign (data_ref, vec_oprnd);
@@ -9567,10 +9563,10 @@ vectorizable_load (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 			&& TREE_CODE (dataref_ptr) == SSA_NAME)
 		      set_ptr_info_alignment (get_ptr_info (dataref_ptr),
 					      align, misalign);
+		    align = least_bit_hwi (misalign | align);
 
 		    if (final_mask)
 		      {
-			align = least_bit_hwi (misalign | align);
 			tree ptr = build_int_cst (ref_type,
 						  align * BITS_PER_UNIT);
 			gcall *call
@@ -9621,14 +9617,10 @@ vectorizable_load (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 			  = fold_build2 (MEM_REF, ltype, dataref_ptr, offset);
 			if (alignment_support_scheme == dr_aligned)
 			  ;
-			else if (DR_MISALIGNMENT (first_dr_info) == -1)
-			  TREE_TYPE (data_ref)
-			    = build_aligned_type (TREE_TYPE (data_ref),
-						  align * BITS_PER_UNIT);
 			else
 			  TREE_TYPE (data_ref)
 			    = build_aligned_type (TREE_TYPE (data_ref),
-						  TYPE_ALIGN (elem_type));
+						  align * BITS_PER_UNIT);
 			if (ltype != vectype)
 			  {
 			    vect_copy_ref_info (data_ref,