[gcc r17-2420] lto: Fix cache partitioning to handle min_partition_size=0

https://gcc.gnu.org/g:6a3f305b298438091ef45f92553618d92a47f8dd

commit r17-2420-g6a3f305b298438091ef45f92553618d92a47f8dd
Author: Michal Jires <[email protected]>
Date:   Mon May 11 21:11:10 2026 +0200

    lto: Fix cache partitioning to handle min_partition_size=0
    
    Cache partitioning asserts that {min,max}_partition_size parameter
    cannot be 0 to prevent later divisions by zero. This is needlessly
    strict, we can clamp the value to 1 to get reasonable/expected behavior.
    
            PR lto/125257
    
    gcc/lto/ChangeLog:
    
            * lto-partition.cc: Handle min/max_partition_size = 0 for
            cache partitioning.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/lto/pr125257_0.c: New test.

Diff:
---
 gcc/lto/lto-partition.cc              | 6 ++----
 gcc/testsuite/gcc.dg/lto/pr125257_0.c | 6 ++++++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/lto/lto-partition.cc b/gcc/lto/lto-partition.cc
index 076cb002a11f..5033ae3f97df 100644
--- a/gcc/lto/lto-partition.cc
+++ b/gcc/lto/lto-partition.cc
@@ -987,11 +987,9 @@ public:
 
 protected:
   partitioner_base (int64_t min_partition_size, int64_t max_partition_size):
-    min_partition_size (min_partition_size),
-    max_partition_size (max_partition_size)
+    min_partition_size (std::max<int64_t>(min_partition_size, 1)),
+    max_partition_size (std::max<int64_t>(max_partition_size, 1))
   {
-    gcc_assert (min_partition_size != 0);
-    gcc_assert (max_partition_size != 0);
   }
   virtual ~partitioner_base ()
   {}
diff --git a/gcc/testsuite/gcc.dg/lto/pr125257_0.c b/gcc/testsuite/gcc.dg/lto/pr125257_0.c
new file mode 100644
index 000000000000..e3821150a18e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr125257_0.c
@@ -0,0 +1,6 @@
+/* PR lto/125257 */
+/* { dg-lto-do link } */
+/* { dg-lto-options { "-O0 -flto --param=lto-min-partition=0 --param=lto-max-partition=0" } } */
+
+int main() {}
+__attribute__((used)) void foo() {}