[pushed: r16-7458] analyzer: fold X + (Y - X) to Y [PR123973]

[David Malcolm]

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Successful run of analyzer integration tests on x86_64-pc-linux-gnu.
Pushed to trunk as r16-7458-g9b090e35cd7536.

gcc/analyzer/ChangeLog:
        PR analyzer/123973
        * region-model-manager.cc
        (region_model_manager::maybe_fold_binop): Fold X + (Y - X) to Y.

gcc/testsuite/ChangeLog:
        PR analyzer/123973
        * c-c++-common/analyzer/infinite-recursion-pr123973.c: New test.

Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
 gcc/analyzer/region-model-manager.cc                       | 5 +++++
 .../c-c++-common/analyzer/infinite-recursion-pr123973.c    | 7 +++++++
 2 files changed, 12 insertions(+)
 create mode 100644 
gcc/testsuite/c-c++-common/analyzer/infinite-recursion-pr123973.c

diff --git a/gcc/analyzer/region-model-manager.cc 
b/gcc/analyzer/region-model-manager.cc
index 1a2a0c740d09f..cfde061d65610 100644
--- a/gcc/analyzer/region-model-manager.cc
+++ b/gcc/analyzer/region-model-manager.cc
@@ -685,6 +685,11 @@ region_model_manager::maybe_fold_binop (tree type, enum 
tree_code op,
        if (unary_op->get_op () == NEGATE_EXPR
            && unary_op->get_arg () == arg0)
          return get_or_create_int_cst (type, 0);
+      /* X + (Y - X) -> Y.  */
+      if (const binop_svalue *bin_op = arg1->dyn_cast_binop_svalue ())
+       if (bin_op->get_op () == MINUS_EXPR)
+         if (bin_op->get_arg1 () == arg0)
+           return get_or_create_cast (type, bin_op->get_arg0 ());
       break;
     case MINUS_EXPR:
       /* (VAL - 0) -> VAL.  */
diff --git a/gcc/testsuite/c-c++-common/analyzer/infinite-recursion-pr123973.c 
b/gcc/testsuite/c-c++-common/analyzer/infinite-recursion-pr123973.c
new file mode 100644
index 0000000000000..56be3a1af8ffa
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/analyzer/infinite-recursion-pr123973.c
@@ -0,0 +1,7 @@
+#define Z 8
+
+void fun(int x, int y)
+{
+  if (x + y > Z)
+    fun(x, Z - x); /* { dg-bogus "infinite recursion" } */
+}
-- 
2.26.3