[gcc r16-245] Infer non-zero for integral division RHS.

[Andrew Macleod via Gcc-cvs]

https://gcc.gnu.org/g:9a467c2ceaa680a3b54a7bc20e6bb6c3f8a47004

commit r16-245-g9a467c2ceaa680a3b54a7bc20e6bb6c3f8a47004
Author: Andrew MacLeod <amacl...@redhat.com>
Date:   Tue Jan 21 11:49:12 2025 -0500

    Infer non-zero for integral division RHS.
    
    Adding op2_range for operator_div allows ranger to notice the divisor
    is non-zero after execution.
    
            PR tree-optimization/95801
            gcc/
            * range-op.cc (operator_div::op2_range): New.
    
            gcc/testsuite/
            * gcc.dg/tree-ssa/pr95801.c: New.

Diff:
---
 gcc/range-op.cc                         | 16 ++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr95801.c | 13 +++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index f72b4ae92cfd..5c0bcdc3b37d 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -2415,8 +2415,11 @@ operator_widen_mult_unsigned::wi_fold (irange &r, tree 
type,
 class operator_div : public cross_product_operator
 {
   using range_operator::update_bitmask;
+  using range_operator::op2_range;
 public:
   operator_div (tree_code div_kind) { m_code = div_kind; }
+  bool op2_range (irange &r, tree type, const irange &lhs, const irange &,
+                 relation_trio) const;
   virtual void wi_fold (irange &r, tree type,
                        const wide_int &lh_lb,
                        const wide_int &lh_ub,
@@ -2436,6 +2439,19 @@ static operator_div op_floor_div (FLOOR_DIV_EXPR);
 static operator_div op_round_div (ROUND_DIV_EXPR);
 static operator_div op_ceil_div (CEIL_DIV_EXPR);
 
+// Set OP2 to non-zero if the LHS isn't UNDEFINED.
+bool
+operator_div::op2_range (irange &r, tree type, const irange &lhs,
+                        const irange &, relation_trio) const
+{
+  if (!lhs.undefined_p ())
+    {
+      r.set_nonzero (type);
+      return true;
+    }
+  return false;
+}
+
 bool
 operator_div::wi_op_overflows (wide_int &res, tree type,
                               const wide_int &w0, const wide_int &w1) const
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr95801.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr95801.c
new file mode 100644
index 000000000000..c3c80a045cf6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr95801.c
@@ -0,0 +1,13 @@
+// { dg-do compile }
+// { dg-options "-O2 -fdump-tree-evrp" }
+
+int always1(int a, int b) {
+    if (a / b)
+        return b != 0;
+    return 1;
+}
+
+// If b != 0 is optimized by recognizing divide by 0 cannot happen,
+// there should be no PHI node.
+
+// { dg-final { scan-tree-dump-not "PHI" "evrp" } }