[COMMITTED] Do not pass NULL to memset in ssa_global_cache.

[Aldy Hernandez <aldyh@redhat.com>]

The code computing ranges in PHIs in the path solver reuses the
temporary ssa_global_cache by calling its clear method.  Calling it on
an empty cache causes us to call memset with NULL.

[The testcase doesn't fail without the patch.  I suppose it needs some
usbsan magic, or to live somewhere else?]

Tested on x86-64 Linux.

gcc/ChangeLog:

	PR tree-optimization/103229
	* gimple-range-cache.cc (ssa_global_cache::clear): Do not pass
	null value to memset.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr103229.c: New test.
---
 gcc/gimple-range-cache.cc       |  3 ++-
 gcc/testsuite/gcc.dg/pr103229.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr103229.c

diff --git a/gcc/gimple-range-cache.cc b/gcc/gimple-range-cache.cc
index a63e20e7e49..b347edeb474 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -651,7 +651,8 @@ ssa_global_cache::clear_global_range (tree name)
 void
 ssa_global_cache::clear ()
 {
-  memset (m_tab.address(), 0, m_tab.length () * sizeof (irange *));
+  if (m_tab.address ())
+    memset (m_tab.address(), 0, m_tab.length () * sizeof (irange *));
 }
 
 // Dump the contents of the global cache to F.
diff --git a/gcc/testsuite/gcc.dg/pr103229.c b/gcc/testsuite/gcc.dg/pr103229.c
new file mode 100644
index 00000000000..96ef9aff67c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr103229.c
@@ -0,0 +1,10 @@
+// { dg-do compile }
+// { dg-options "-O -w" }
+
+int main() {
+  int i;
+  for (; i;)
+    ;
+
+  return 0;
+}
-- 
2.31.1