From 1f4590e7a633c6335512b012578bddba7602b3c9 Mon Sep 17 00:00:00 2001 From: Yury Gribov Date: Sun, 28 May 2017 21:02:20 +0100 Subject: [PATCH] Added no_tail_call attribute. gcc/ 2017-05-29 Yury Gribov * cgraphunit.c (cgraph_node::expand_thunk): Prevent tailcalling functions marked with no_tail_call. * gcc/doc/extend.texi: Document no_tail_call. * tree-tailcall.c (find_tail_calls): Ditto. * tree.c (comp_type_attributes): Treat no_tail_call mismatch as error. gcc/c-family/ 2017-05-29 Yury Gribov * c-attribs.c: New attribute. gcc/testsuite/ 2017-05-29 Yury Gribov * gcc.dg/pr66826-1.c: New test. * gcc.dg/pr66826-2.c: New test. --- gcc/c-family/c-attribs.c | 1 + gcc/cgraphunit.c | 6 ++++-- gcc/doc/extend.texi | 7 +++++++ gcc/testsuite/gcc.dg/pr66826-1.c | 14 ++++++++++++++ gcc/testsuite/gcc.dg/pr66826-2.c | 6 ++++++ gcc/tree-tailcall.c | 4 ++++ gcc/tree.c | 7 ++++--- 7 files changed, 40 insertions(+), 5 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr66826-1.c create mode 100644 gcc/testsuite/gcc.dg/pr66826-2.c diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c index 695c58c..482db00 100644 --- a/gcc/c-family/c-attribs.c +++ b/gcc/c-family/c-attribs.c @@ -345,6 +345,7 @@ const struct attribute_spec c_common_attribute_table[] = handle_bnd_instrument, false }, { "fallthrough", 0, 0, false, false, false, handle_fallthrough_attribute, false }, + { "no_tail_call", 0, 0, false, true, true, NULL, true }, { NULL, 0, 0, false, false, false, NULL, false } }; diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c index 4a949ca..e23fd21 100644 --- a/gcc/cgraphunit.c +++ b/gcc/cgraphunit.c @@ -1715,6 +1715,7 @@ cgraph_node::expand_thunk (bool output_asm_thunks, bool force_gimple_thunk) tree resdecl; tree restmp = NULL; tree resbnd = NULL; + bool no_tail_call_p; gcall *call; greturn *ret; @@ -1823,6 +1824,7 @@ cgraph_node::expand_thunk (bool output_asm_thunks, bool force_gimple_thunk) callees->call_stmt = call; gimple_call_set_from_thunk (call, true); gimple_call_set_with_bounds (call, instrumentation_clone); + no_tail_call_p = lookup_attribute ("no_tail_call", TYPE_ATTRIBUTES (gimple_call_fntype (call))); /* Return slot optimization is always possible and in fact requred to return values with DECL_BY_REFERENCE. */ @@ -1912,7 +1914,7 @@ cgraph_node::expand_thunk (bool output_asm_thunks, bool force_gimple_thunk) bsi = gsi_last_bb (return_bb); } } - else + else if (!no_tail_call_p) gimple_call_set_tail (call, true); /* Build return value. */ @@ -1924,7 +1926,7 @@ cgraph_node::expand_thunk (bool output_asm_thunks, bool force_gimple_thunk) gsi_insert_after (&bsi, ret, GSI_NEW_STMT); } - else + else if (!no_tail_call_p) { gimple_call_set_tail (call, true); remove_edge (single_succ_edge (bb)); diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index c737634..6fa9c66 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -3067,6 +3067,13 @@ the standard C library can be guaranteed not to throw an exception with the notable exceptions of @code{qsort} and @code{bsearch} that take function pointer arguments. +@item no_tail_call +@cindex @code{no_tail_call} function attribute +The @code{no_tail_call} attribute is used to prohibit tail-call +optimization of a function. When taking address of function +marked with @code{no_tail_call}, resulting function pointer type must +have this attribute set too. + @item optimize @cindex @code{optimize} function attribute The @code{optimize} attribute is used to specify that a function is to diff --git a/gcc/testsuite/gcc.dg/pr66826-1.c b/gcc/testsuite/gcc.dg/pr66826-1.c new file mode 100644 index 0000000..eac8ba9 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr66826-1.c @@ -0,0 +1,14 @@ +/* { dg-do compile { target x86_64-*-* } } */ +/* { dg-options "-O2" } */ + +int tail(); + +__attribute__((no_tail_call)) int notail(); + +int foo1() { + return tail(); /* { dg-final { scan-assembler "jmp.*\\ytail" } } */ +} + +int foo2() { + return notail(); /* { dg-final { scan-assembler "call.*\\ynotail" } } */ +} diff --git a/gcc/testsuite/gcc.dg/pr66826-2.c b/gcc/testsuite/gcc.dg/pr66826-2.c new file mode 100644 index 0000000..a22df8b --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr66826-2.c @@ -0,0 +1,6 @@ +__attribute__((no_tail_call)) int foo(); + +int bar() { + int (*p)() = foo; /* { dg-error "initialization from incompatible pointer type" } */ + return p(); +} diff --git a/gcc/tree-tailcall.c b/gcc/tree-tailcall.c index f586edc..30a6fad 100644 --- a/gcc/tree-tailcall.c +++ b/gcc/tree-tailcall.c @@ -601,6 +601,10 @@ find_tail_calls (basic_block bb, struct tailcall **ret) if (m && POINTER_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl)))) return; + /* See if function does not want to be tailcalled. */ + if (lookup_attribute ("no_tail_call", TYPE_ATTRIBUTES (gimple_call_fntype (call)))) + return; + nw = XNEW (struct tailcall); nw->call_gsi = gsi; diff --git a/gcc/tree.c b/gcc/tree.c index b76b521..47e1ea4 100644 --- a/gcc/tree.c +++ b/gcc/tree.c @@ -5034,7 +5034,7 @@ comp_type_attributes (const_tree type1, const_tree type2) const_tree attr; as = lookup_attribute_spec (get_attribute_name (a)); - if (!as || as->affects_type_identity == false) + if (!as || !as->affects_type_identity) continue; attr = lookup_attribute (as->name, CONST_CAST_TREE (a2)); @@ -5048,7 +5048,7 @@ comp_type_attributes (const_tree type1, const_tree type2) const struct attribute_spec *as; as = lookup_attribute_spec (get_attribute_name (a)); - if (!as || as->affects_type_identity == false) + if (!as || !as->affects_type_identity) continue; if (!lookup_attribute (as->name, CONST_CAST_TREE (a1))) @@ -5061,7 +5061,8 @@ comp_type_attributes (const_tree type1, const_tree type2) if (!a) return 1; } - if (lookup_attribute ("transaction_safe", CONST_CAST_TREE (a))) + if (lookup_attribute ("transaction_safe", CONST_CAST_TREE (a)) + || lookup_attribute ("no_tail_call", CONST_CAST_TREE (a))) return 0; /* As some type combinations - like default calling-convention - might be compatible, we have to call the target hook to get the final result. */ -- 2.7.4