[PATCH] ranger: Fix up range computation for CLZ [PR116486]

[Jakub Jelinek]

Hi!

The initial CLZ gimple-range-op.cc implementation handled just the
case where second argument to .CLZ is equal to prec, but in
r15-1014 I've added also handling of the -1 case.  As the following
testcase shows, incorrectly though for the case where the first argument
has [0,0] range.  If the second argument is prec, then the result should
be [prec,prec] and that was handled correctly, but when the second argument
is -1, the result should be [-1,-1] but instead it was incorrectly computed
as [prec-1,prec-1] (when second argument is prec, mini is 0 and maxi is
prec, while when second argument is -1, mini is -1 and maxi is prec-1).

Fixed thusly (the actual handling is then similar to the CTZ [0,0] case),
bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-09-02  Jakub Jelinek  <ja...@redhat.com>

        PR middle-end/116486
        * gimple-range-op.cc (cfn_clz::fold_range): If lh is [0,0]
        and mini is -1, return [-1,-1] range rather than [prec-1,prec-1].

        * gcc.dg/bitint-109.c: New test.

--- gcc/gimple-range-op.cc.jj   2024-08-15 10:18:48.000000000 +0200
+++ gcc/gimple-range-op.cc      2024-08-31 18:23:14.547269372 +0200
@@ -972,8 +972,10 @@ cfn_clz::fold_range (irange &r, tree typ
     {
       // If CLZ_DEFINED_VALUE_AT_ZERO is 2 with VALUE of prec,
       // return [prec, prec] or [-1, -1], otherwise ignore the range.
-      if (maxi == prec || mini == -1)
-       mini = maxi;
+      if (maxi == prec)
+       mini = prec;
+      else if (mini == -1)
+       maxi = -1;
     }
   else if (mini >= 0)
     mini = newmini;
--- gcc/testsuite/gcc.dg/bitint-109.c.jj        2024-08-31 18:25:15.111715665 
+0200
+++ gcc/testsuite/gcc.dg/bitint-109.c   2024-08-31 18:26:02.015118452 +0200
@@ -0,0 +1,25 @@
+/* PR middle-end/116486 */
+/* { dg-do run { target bitint } } */
+/* { dg-options "-O2 -fno-tree-ccp" } */
+
+unsigned u;
+
+#if __BITINT_MAXWIDTH__ >= 129
+#define N 0x100000000000000000000000000000000uwb
+#else
+#define N 0xffffffffffffffffuwb
+#endif
+
+int
+foo (void)
+{
+  return __builtin_stdc_first_leading_one (u / N);
+}
+
+int
+main ()
+{
+  int x = foo ();
+  if (x)
+    __builtin_abort ();
+}

        Jakub