Re: [PATCH] Fix vectorization of POINTER_DIFF_EXPR (PR tree-optimization/83338)

[Richard Biener <rguenther at suse dot de>]

On December 9, 2017 10:50:12 AM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>When POINTER_PLUS_EXPR is vectorized, we vectorize it as a vector
>PLUS_EXPR.
>This (usually?  Not sure about targets where sizetype has different
>precision from POINTER_SIZE; maybe those just don't have vector types)
>works
>because we vectorize pointer variables as vectors of unsigned pointer
>sized
>integers and if sizetype has the same precision, then it is the same
>vector
>too, so both operands and result are compatible vectors.
>
>POINTER_DIFF_EXPR is different, the arguments are pointers which get
>vectype of vectors of unsigned pointer sized integers, but the result
>is a corresponding signed type, so vectype_out is vector of signed
>pointer
>sized integers; those aren't compatible.
>
>So, we can't just vectorize POINTER_DIFF_EXPR as vector MINUS_EXPR, we
>need
>to VCE the result from vectype to vectype_out.
>
>Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok
>for
>trunk?

OK. 

Richard. 


>2017-12-09  Jakub Jelinek  <jakub@redhat.com>
>
>	PR tree-optimization/83338
>	* tree-vect-stmts.c (vectorizable_operation): Handle POINTER_DIFF_EXPR
>	vectorization as MINUS_EXPR with a subsequent VIEW_CONVERT_EXPR from
>	vector of unsigned integers to vector of signed integers.
>
>	* gcc.dg/vect/pr83338.c: New test.
>
>--- gcc/tree-vect-stmts.c.jj	2017-12-08 12:21:58.000000000 +0100
>+++ gcc/tree-vect-stmts.c	2017-12-09 00:55:17.614147824 +0100
>@@ -5226,7 +5226,7 @@ vectorizable_operation (gimple *stmt, gi
>   stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
>   tree vectype;
>   loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
>-  enum tree_code code;
>+  enum tree_code code, orig_code;
>   machine_mode vec_mode;
>   tree new_temp;
>   int op_type;
>@@ -5264,7 +5264,7 @@ vectorizable_operation (gimple *stmt, gi
>   if (TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME)
>     return false;
> 
>-  code = gimple_assign_rhs_code (stmt);
>+  orig_code = code = gimple_assign_rhs_code (stmt);
> 
>   /* For pointer addition and subtraction, we should use the normal
>      plus and minus for the vector operation.  */
>@@ -5455,6 +5455,14 @@ vectorizable_operation (gimple *stmt, gi
>   /* Handle def.  */
>   vec_dest = vect_create_destination_var (scalar_dest, vectype);
> 
>+  /* POINTER_DIFF_EXPR has pointer arguments which are vectorized as
>+     vectors with unsigned elements, but the result is signed.  So, we
>+     need to compute the MINUS_EXPR into vectype temporary and
>+     VIEW_CONVERT_EXPR it into the final vectype_out result.  */
>+  tree vec_cvt_dest = NULL_TREE;
>+  if (orig_code == POINTER_DIFF_EXPR)
>+    vec_cvt_dest = vect_create_destination_var (scalar_dest,
>vectype_out);
>+
>   /* In case the vectorization factor (VF) is bigger than the number
> of elements that we can fit in a vectype (nunits), we have to generate
>      more than one vector stmt - i.e - we need to "unroll" the
>@@ -5546,6 +5554,15 @@ vectorizable_operation (gimple *stmt, gi
> 	  new_temp = make_ssa_name (vec_dest, new_stmt);
> 	  gimple_assign_set_lhs (new_stmt, new_temp);
> 	  vect_finish_stmt_generation (stmt, new_stmt, gsi);
>+	  if (vec_cvt_dest)
>+	    {
>+	      new_temp = build1 (VIEW_CONVERT_EXPR, vectype_out, new_temp);
>+	      new_stmt = gimple_build_assign (vec_cvt_dest,
>VIEW_CONVERT_EXPR,
>+					      new_temp);
>+	      new_temp = make_ssa_name (vec_cvt_dest, new_stmt);
>+	      gimple_assign_set_lhs (new_stmt, new_temp);
>+	      vect_finish_stmt_generation (stmt, new_stmt, gsi);
>+	    }
>           if (slp_node)
> 	    SLP_TREE_VEC_STMTS (slp_node).quick_push (new_stmt);
>         }
>--- gcc/testsuite/gcc.dg/vect/pr83338.c.jj	2017-12-09
>01:00:06.602565622 +0100
>+++ gcc/testsuite/gcc.dg/vect/pr83338.c	2017-12-09 01:00:18.297422116
>+0100
>@@ -0,0 +1,10 @@
>+/* PR tree-optimization/83338 */
>+/* { dg-do compile } */
>+
>+void
>+foo (char **p, char **q, __PTRDIFF_TYPE__ *r)
>+{
>+  int i;
>+  for (i = 0; i < 1024; i++)
>+    r[i] = p[i] - q[i];
>+}
>
>
>	Jakub