[gcc r12-10766] Remove buggy special case in irange::invert [PR109934].

[Sam James via Gcc-cvs]

https://gcc.gnu.org/g:ea7d7818fdc7a49be3d35acd441ce122e8bb477e

commit r12-10766-gea7d7818fdc7a49be3d35acd441ce122e8bb477e
Author: Aldy Hernandez <al...@redhat.com>
Date:   Tue May 23 12:34:45 2023 +0200

    Remove buggy special case in irange::invert [PR109934].
    
    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)

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

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 000bbcf8917e..cf57e695e47e 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -1856,14 +1856,6 @@ irange::invert ()
   signop sign = TYPE_SIGN (ttype);
   wide_int type_min = wi::min_value (prec, sign);
   wide_int type_max = wi::max_value (prec, sign);
-  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;
-    }
   // The algorithm is as follows.  To calculate INVERT ([a,b][c,d]), we
   // generate [-MIN, a-1][b+1, c-1][d+1, MAX].
   //