From e17c0599bac6d614c994ea9a795f024164f689e5 Mon Sep 17 00:00:00 2001 From: Richard Lowe Date: Sun, 30 Sep 2012 16:44:14 -0400 Subject: [PATCH 06/39] allow the global disabling of function cloning Optimizations which clone functions to create call-specific implementations which may be better optimized also dissociate these functions from their symbol names in ways harmful to tracing and debugging (since there are now several implementations of a single source symbol, quite possibly none of them having the actual source symbol name). This allows any function cloning to be disabled, and makes any such optimization ineffective, and our source safe for debuggers everywhere. --- gcc/attribs.cc | 9 +++++++++ gcc/common.opt | 5 +++++ gcc/doc/invoke.texi | 10 ++++++++++ 3 files changed, 24 insertions(+) diff --git a/gcc/attribs.cc b/gcc/attribs.cc index 56dd18c2fa8..129588d67ec 100644 --- a/gcc/attribs.cc +++ b/gcc/attribs.cc @@ -713,6 +713,15 @@ decl_attributes (tree *node, tree attributes, int flags, attributes = tree_cons (get_identifier ("no_icf"), NULL, attributes); } + /* If the user passed -fno-clone-functions, all functions should be treated + as "noclone" */ + if (TREE_CODE (*node) == FUNCTION_DECL + && !flag_clone_functions) + { + if (lookup_attribute ("noclone", attributes) == NULL) + attributes = tree_cons (get_identifier ("noclone"), NULL, attributes); + } + targetm.insert_attributes (*node, &attributes); /* Note that attributes on the same declaration are not necessarily diff --git a/gcc/common.opt b/gcc/common.opt index 324f11ba131..a37f1126069 100644 --- a/gcc/common.opt +++ b/gcc/common.opt @@ -1264,6 +1264,11 @@ fcode-hoisting Common Var(flag_code_hoisting) Optimization Enable code hoisting. +fclone-functions +Common Var(flag_clone_functions) Init(1) +Allow the compiler to clone functions to facilitate certain optimizations. +Enabled by default. + fcombine-stack-adjustments Common Var(flag_combine_stack_adjustments) Optimization Looks for opportunities to reduce stack adjustments and stack references. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index f60e50ca3bd..7d75466d290 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -574,6 +574,7 @@ Objective-C and Objective-C++ Dialects}. -fassociative-math -fauto-profile -fauto-profile[=@var{path}] -fauto-inc-dec -fbranch-probabilities -fcaller-saves +-fclone-functions -fcombine-stack-adjustments -fconserve-stack -ffold-mem-offsets -fcompare-elim -fcprop-registers -fcrossjumping @@ -13796,6 +13797,15 @@ and then tries to find ways to combine them. Enabled by default at @option{-O1} and higher. +@opindex fno-clone-functions +@item -fno-clone-functions +Forbid the implicit cloning of functions implicit in certain +optimizations. This also effectively will disable any optimization +which wishes to clone functions, equivalent to each function having +the ``noclone'' attribute. This allows the prevention of the +dissociation of a piece of text from an intelligible and expected +symbol name, which may hamper debugging and tracing. + @opindex fipa-ra @item -fipa-ra Use caller save registers for allocation if those registers are not used by -- 2.53.0