[gcc r16-7549] tree-optimization/124132 - fix type problem in loop splitting

[Richard Biener]

https://gcc.gnu.org/g:9a5ee941a2cc525811748f78d42a36d1100c12d7

commit r16-7549-g9a5ee941a2cc525811748f78d42a36d1100c12d7
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Feb 17 11:05:45 2026 +0100

    tree-optimization/124132 - fix type problem in loop splitting
    
    The following fixes the computation of the 2nd loop IV bound after
    loop splitting when only one of the split IV and the loop control
    variable is a pointer.
    
            PR tree-optimization/124132
            * tree-ssa-loop-split.cc (compute_new_first_bound): Fix
            bound difference computation.
    
            * gcc.dg/torture/pr124132.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr124132.c | 16 ++++++++++++++++
 gcc/tree-ssa-loop-split.cc              | 19 ++++++++-----------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr124132.c b/gcc/testsuite/gcc.dg/torture/pr124132.c
new file mode 100644
index 000000000000..8d14fc0346d2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr124132.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-w" } */
+
+char slow_mul1_dst1, code_some_shards___gf_mulc__0, code_some_shards_lim;
+long slow_mul1_dst_max;
+long long code_some_shards_pos;
+void code_some_shards()
+{
+  char *dst = &slow_mul1_dst1;
+  for (; dst < &code_some_shards_lim; dst++)
+    {
+      if (code_some_shards_pos < slow_mul1_dst_max)
+        *dst = code_some_shards___gf_mulc__0;
+      code_some_shards_pos += 1;
+    }
+}
diff --git a/gcc/tree-ssa-loop-split.cc b/gcc/tree-ssa-loop-split.cc
index ba6cc45d7f03..722383a420ac 100644
--- a/gcc/tree-ssa-loop-split.cc
+++ b/gcc/tree-ssa-loop-split.cc
@@ -458,21 +458,15 @@ compute_new_first_bound (gimple_seq *stmts, class tree_niter_desc *niter,
   tree end = force_gimple_operand (niter->bound, &stmts2,
 					true, NULL_TREE);
   gimple_seq_add_seq_without_update (stmts, stmts2);
-  if (POINTER_TYPE_P (TREE_TYPE (enddiff)))
-    {
-      tree tem = gimple_convert (stmts, sizetype, enddiff);
-      tem = gimple_build (stmts, NEGATE_EXPR, sizetype, tem);
-      enddiff = gimple_build (stmts, POINTER_PLUS_EXPR,
-			      TREE_TYPE (enddiff),
-			      end, tem);
-    }
+  if (POINTER_TYPE_P (TREE_TYPE (controlbase)))
+    enddiff = gimple_build (stmts, POINTER_DIFF_EXPR,
+			    ssizetype, end, enddiff);
   else
     enddiff = gimple_build (stmts, MINUS_EXPR, TREE_TYPE (enddiff),
 			    end, enddiff);
 
   /* Compute guard_init + (end-beg).  */
   tree newbound;
-  enddiff = gimple_convert (stmts, TREE_TYPE (guard_init), enddiff);
   if (POINTER_TYPE_P (TREE_TYPE (guard_init)))
     {
       enddiff = gimple_convert (stmts, sizetype, enddiff);
@@ -481,8 +475,11 @@ compute_new_first_bound (gimple_seq *stmts, class tree_niter_desc *niter,
 			       guard_init, enddiff);
     }
   else
-    newbound = gimple_build (stmts, PLUS_EXPR, TREE_TYPE (guard_init),
-			     guard_init, enddiff);
+    {
+      enddiff = gimple_convert (stmts, TREE_TYPE (guard_init), enddiff);
+      newbound = gimple_build (stmts, PLUS_EXPR, TREE_TYPE (guard_init),
+			       guard_init, enddiff);
+    }
 
   /* Depending on the direction of the IVs the new bound for the first
      loop is the minimum or maximum of old bound and border.