[PATCH] gimple-fold: Verify builtin prototype before folding [PR93927]

[Jakub Jelinek]

Hi!

The following patch does the same check the tree-ssa-strlen.c pass does
to punt on broken builtin redeclarations.
I agree the ultimate fix is change the C FE, but don't feel I know that part
of the FE good enough to know all the consequences and so it might be too
risky for stage4.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2020-02-26  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/93927
        * gimple-fold.c (gimple_fold_builtin): Punt if callee has incompatible
        prototype.

        * gcc.c-torture/compile/pr93927-1.c: New test.
        * gcc.c-torture/compile/pr93927-2.c: New test.

--- gcc/gimple-fold.c.jj        2020-02-06 09:13:21.732085293 +0100
+++ gcc/gimple-fold.c   2020-02-25 11:46:14.863796864 +0100
@@ -3906,6 +3906,12 @@ gimple_fold_builtin (gimple_stmt_iterato
   if (avoid_folding_inline_builtin (callee))
     return false;
 
+  tree decl = builtin_decl_explicit (DECL_FUNCTION_CODE (callee));
+  if (decl
+      && decl != callee
+      && !gimple_builtin_call_types_compatible_p (stmt, decl))
+    return false;
+
   unsigned n = gimple_call_num_args (stmt);
   enum built_in_function fcode = DECL_FUNCTION_CODE (callee);
   switch (fcode)
--- gcc/testsuite/gcc.c-torture/compile/pr93927-1.c.jj  2020-02-25 
11:47:10.983971425 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr93927-1.c     2020-02-25 
11:46:43.004382966 +0100
@@ -0,0 +1,9 @@
+/* PR tree-optimization/93927 */
+
+__SIZE_TYPE__ strstr (const char *, const char *);
+
+char *
+foo (char *x)
+{
+  return !!strstr (x, "0") ? "0" : "1";
+}
--- gcc/testsuite/gcc.c-torture/compile/pr93927-2.c.jj  2020-02-25 
11:47:13.930928081 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr93927-2.c     2020-02-25 
11:46:57.304172632 +0100
@@ -0,0 +1,9 @@
+/* PR tree-optimization/93927 */
+
+__SIZE_TYPE__ strchr (const char *, int);
+
+char *
+foo (char *x)
+{
+  return !!strchr (x, 0) ? "0" : "1";
+}

        Jakub