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[releases/gcc-13,2/2] Remove buggy special case in irange::invert [PR109934].

Message ID ab19ccc3ba9b1d6559039e0c6d37f2b9280bb870.1728822647.git.sam@gentoo.org
State New
Headers show
Series Two backports (Valgrind noise, wrong-code) | expand

Commit Message

Sam James Oct. 13, 2024, 12:30 p.m. UTC 
From: Aldy Hernandez <aldyh@redhat.com>

This patch removes a buggy special case in irange::invert which seems
to have been broken for a while, and probably never triggered because
the legacy code was handled elsewhere, and the non-legacy code was
using an int_range_max of int_range<255> which made it extremely
likely for num_ranges == 255.  However, with auto-resizing ranges,
int_range_max will start off at 3 and can hit this bogus code in the
unswitching code.

	PR tree-optimization/109934

gcc/ChangeLog:

	* value-range.cc (irange::invert): Remove buggy special case.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr109934.c: New test.

(cherry picked from commit 8d5f050dabbf6dd3b992c3b46661848dbcf30d9e)
---
I'm testing this for 12 as well. OK for 13 (and 12 if no regressions)?

 gcc/testsuite/gcc.dg/tree-ssa/pr109934.c | 22 ++++++++++++++++++++++
 gcc/value-range.cc                       |  8 --------
 2 files changed, 22 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr109934.c
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Patch

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr109934.c b/gcc/testsuite/gcc.dg/tree-ssa/pr109934.c
new file mode 100644
index 000000000000..08bd5ce95c61
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr109934.c
@@ -0,0 +1,22 @@ 
+// { dg-do run }
+// { dg-options "-O3" }
+
+int printf(const char *, ...);
+short a;
+long b = 3, c;
+int d(int e) {
+  switch (e)
+  case 111:
+  case 222:
+  case 44:
+    return 0;
+  return e;
+}
+int main() {
+  for (; a >= 0; --a)
+    if (d(c + 23) - 23)
+      b = 0;
+
+  if (b != 3)
+    __builtin_abort ();
+}
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index 753f5e8cc769..1ac62e3018e1 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -2833,14 +2833,6 @@  irange::invert ()
   wide_int type_min = wi::min_value (prec, sign);
   wide_int type_max = wi::max_value (prec, sign);
   m_nonzero_mask = NULL;
-  if (m_num_ranges == m_max_ranges
-      && lower_bound () != type_min
-      && upper_bound () != type_max)
-    {
-      m_base[1] = wide_int_to_tree (ttype, type_max);
-      m_num_ranges = 1;
-      return;
-    }
 
   // At this point, we need one extra sub-range to represent the
   // inverse.