From: Aldy Hernandez <aldyh@redhat.com>
Date: Wed, 12 May 2021 19:22:15 +0000 (-0400)
Subject: Skip out on processing __builtin_clz when varying.
X-Git-Tag: basepoints/gcc-13~7558
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d902a1b57606536982a1001670f998de685eaf7c;p=thirdparty%2Fgcc.git

Skip out on processing __builtin_clz when varying.

The previous changes to irange::constant_p return TRUE for
VARYING, since VARYING has numerical end points like any other
constant range.  The problem is that some users of constant_p
depended on constant_p excluding the full domain.  The
range handler for __builtin_clz, that is shared between ranger
and vr_values, is one such user.

This patch excludes varying_p(), to match the original behavior
for clz.

gcc/ChangeLog:

	PR c/100521
	* gimple-range.cc (range_of_builtin_call): Skip out on
	  processing __builtin_clz when varying.
---

diff --git a/gcc/gimple-range.cc b/gcc/gimple-range.cc
index e94bb355de34..5b288d8e6a7e 100644
--- a/gcc/gimple-range.cc
+++ b/gcc/gimple-range.cc
@@ -737,7 +737,7 @@ range_of_builtin_call (range_query &query, irange &r, gcall *call)
 
       query.range_of_expr (r, arg, call);
       // From clz of minimum we can compute result maximum.
-      if (r.constant_p ())
+      if (r.constant_p () && !r.varying_p ())
 	{
 	  int newmaxi = prec - 1 - wi::floor_log2 (r.lower_bound ());
 	  // Argument is unsigned, so do nothing if it is [0, ...] range.
diff --git a/gcc/testsuite/gcc.dg/pr100521.c b/gcc/testsuite/gcc.dg/pr100521.c
new file mode 100644
index 000000000000..fd9f0db54126
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr100521.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int
+__builtin_clz (int a)
+{
+  return __builtin_clz(a);
+}