[gcc r13-4488] gimple-fold: Refine gimple_fold_partial_load_store_mem_ref [PR107412]

[Kewen Lin <linkw@gcc.gnu.org>]

https://gcc.gnu.org/g:380d62c14c99d8df13b7a86660e7ee67d01ad827

commit r13-4488-g380d62c14c99d8df13b7a86660e7ee67d01ad827
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Sun Dec 4 23:27:08 2022 -0600

    gimple-fold: Refine gimple_fold_partial_load_store_mem_ref [PR107412]
    
    Following Richard's review comments, this patch is to use
    untruncated type for the length used for IFN_LEN_{LOAD,STORE}
    instead of "unsigned int" for better robustness.  It also
    avoid to use to_constant and tree arithmetic for subtraction.
    
    Co-authored-by: Richard Sandiford  <richard.sandiford@arm.com>
    
            PR tree-optimization/107412
    
    gcc/ChangeLog:
    
            * gimple-fold.cc (gimple_fold_partial_load_store_mem_ref): Use
            untruncated type for the length, and avoid to_constant and tree
            arithmetic for subtraction.

Diff:
---
 gcc/gimple-fold.cc | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index c2d9c806aee..88d14c7adcc 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -5387,18 +5387,17 @@ gimple_fold_partial_load_store_mem_ref (gcall *call, tree vectype, bool mask_p)
       tree mask = gimple_call_arg (call, 2);
       if (!integer_all_onesp (mask))
 	return NULL_TREE;
-    } else {
+    }
+  else
+    {
       tree basic_len = gimple_call_arg (call, 2);
-      if (!tree_fits_uhwi_p (basic_len))
+      if (!poly_int_tree_p (basic_len))
 	return NULL_TREE;
       unsigned int nargs = gimple_call_num_args (call);
       tree bias = gimple_call_arg (call, nargs - 1);
-      gcc_assert (tree_fits_shwi_p (bias));
-      tree biased_len = int_const_binop (MINUS_EXPR, basic_len, bias);
-      unsigned int len = tree_to_uhwi (biased_len);
-      unsigned int vect_len
-	= GET_MODE_SIZE (TYPE_MODE (vectype)).to_constant ();
-      if (vect_len != len)
+      gcc_assert (TREE_CODE (bias) == INTEGER_CST);
+      if (maybe_ne (wi::to_poly_widest (basic_len) - wi::to_widest (bias),
+		    GET_MODE_SIZE (TYPE_MODE (vectype))))
 	return NULL_TREE;
     }