[gcc r13-3476] tree-optimization/100756 - niter analysis and folding

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:19295e8607da2f743368fe6f5708146616aafa91

commit r13-3476-g19295e8607da2f743368fe6f5708146616aafa91
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Oct 24 09:51:32 2022 +0200

    tree-optimization/100756 - niter analysis and folding
    
    niter analysis, specifically the part trying to simplify the computed
    maybe_zero condition against the loop header copying condition, is
    confused by us now simplifying
    
      _15 = n_8(D) * 4;
      if (_15 > 0)
    
    to
    
      _15 = n_8(D) * 4;
      if (n_8(D) > 0)
    
    which is perfectly sound at the point we do this transform.  One
    solution might be to involve ranger in this simplification, another
    is to be more aggressive when expanding expressions - the condition
    we try to simplify is _15 > 0, so all we need is expanding that
    to n_8(D) * 4 > 0.
    
    The following does just that.
    
            PR tree-optimization/100756
            * tree-ssa-loop-niter.cc (expand_simple_operations): Also
            expand multiplications by invariants.
    
            * gcc.dg/vect/pr100756.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr100756.c | 15 +++++++++++++++
 gcc/tree-ssa-loop-niter.cc           |  1 +
 2 files changed, 16 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/vect/pr100756.c b/gcc/testsuite/gcc.dg/vect/pr100756.c
new file mode 100644
index 00000000000..c1362f29ebe
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr100756.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int } */
+
+int
+foo (int * restrict a, int n)
+{
+  int i, result = 0;
+
+  a = __builtin_assume_aligned (a, __BIGGEST_ALIGNMENT__);
+  for (i = 0; i < n * 4; i++)
+    result += a[i];
+  return result;
+}
+
+/* { dg-final { scan-tree-dump-not "epilog loop required" "vect" } } */
diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
index 1e0f609d8b6..4ffcef4f4ff 100644
--- a/gcc/tree-ssa-loop-niter.cc
+++ b/gcc/tree-ssa-loop-niter.cc
@@ -2216,6 +2216,7 @@ expand_simple_operations (tree expr, tree stop, hash_map<tree, tree> &cache)
 
     case PLUS_EXPR:
     case MINUS_EXPR:
+    case MULT_EXPR:
       if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (expr))
 	  && TYPE_OVERFLOW_TRAPS (TREE_TYPE (expr)))
 	return expr;