https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65887
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to vries from comment #2) > I. > After removing the copyback using attached patch, and marking the va_arg > first argument as addressable as suggested here ( > https://gcc.gnu.org/ml/gcc-patches/2015-04/msg01314.html ) using this patch > (nr 1): > ... > @@ -9408,6 +9458,23 @@ gimplify_va_arg_expr (tree *expr_p, gimple_seq *pre_p, > } > > /* Transform a VA_ARG_EXPR into an VA_ARG internal function. */ > + mark_addressable (valist); > ap = build_fold_addr_expr_loc (loc, valist); > tag = build_int_cst (build_pointer_type (type), 0); > *expr_p = build_call_expr_internal_loc (loc, IFN_VA_ARG, type, 2, ap, > tag); > ... > > we get the desired: > ... > e = VA_ARG (&argp, 0B); > e = VA_ARG (&argp, 0B); > ... > > > II. > However, we subsequently run into a verify_gimple_call failure in > gcc.c-torture/execute/va-arg-10.c, for the second argument of this va_copy: > ... > __builtin_va_copy (&apc, ap); > ... > D.2056 = VA_ARG (&ap, 0B); > ... > > Presumably because ap is not marked as addressable when gimplifying the > va_copy, but ap is later marked as addressable when gimplifying VA_ARG_EXPR. > > With this patch (nr 2), we mark the second va_copy argument as addressable > when gimplifying va_copy: > ... > @@ -2339,6 +2340,55 @@ gimplify_call_expr (tree *expr_p, gimple_seq *pre_p, > bool want_value) > && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL) > switch (DECL_FUNCTION_CODE (fndecl)) > { > + case BUILT_IN_VA_COPY: > + mark_addressable (CALL_EXPR_ARG (*expr_p, 1)); > + break; > case BUILT_IN_VA_START: > { > builtin_va_start_p = TRUE; > ... > > That indeed prevents the verify_gimple_call error. But the code now contains > a copy: > ... > ap.0 = ap; > __builtin_va_copy (&apc, ap.0); > ... > D.2057 = VA_ARG (&ap, 0B); > ... > The copy in itself does not look incorrect, but we'd rather not have it. > > > III. > Furthermore, patch nr 1 triggers a verify_gimple_call error on > gcc.c-torture/execute/va-arg-14.c for the first argument of a va_copy: > ... > __builtin_va_copy (param, &local); > ... > D.1845 = VA_ARG (¶m, 0B); > ... > > Using this patch (nr 3), we also mark the first argument of the copy as > addressable: > ... > @@ -2341,6 +2341,7 @@ gimplify_call_expr (tree *expr_p, gimple_seq *pre_p, > bool want_value) > { > case BUILT_IN_VA_COPY: > mark_addressable (CALL_EXPR_ARG (*expr_p, 1)); > + mark_addressable (CALL_EXPR_ARG (*expr_p, 0)); > break; > case BUILT_IN_VA_START: > { > ... > > That indeed prevents the verify_gimple_call failure. But it results in this > code: > ... > param.0 = param; > __builtin_va_copy (param.0, &local); > ... > D.1846 = VA_ARG (¶m, 0B); > ... > which doesn't look correct: param is unmodified by the va_copy. Well, you only get the "copy" if param is of register type (thus a pointer). So the code is correct I belive. Rather than marking the va_list arg addressable in all the cases above you should probably simply ensure the frontend marks it so from the point it creates a variable with va_list type. This is because even va_list a1, a2; a1 = a2; __builtin_va_arg (a1, ...); might go wrong when gimplifying a1 = a2. > OTOH, the obvious tests (execute.exp=va-arg*.c, execute.exp=stdarg*.c, > callabi.exp) are passing, probably because va_list is a pointer type, and > va_copy modifies what param points to.
