[PATCH 1/9] ENABLE_CHECKING refactoring

[Mikhail Maltsev <maltsevm at gmail dot com>]

Hi!

This is an updated series of patches which converts 'ENABLE_CHECKING' macro into
a flag, 'flag_checking' (and 'CHECKING_P' macro in several cases). For now
flag_checking is always initialized with the value of 'CHECKING_P', but later it
can be turned into a proper command-line flag and probably split into several
checks. I also added several function which verify internal data structures when
flag_checking is enabled (e.g. checking_verify_flow_info which calls
verify_flow_info). These functions make their callers look somewhat cleaner.

The cases where I left 'CHECKING_P' are:
1. libcpp (turn ICE after an error into fatal error) and pretty-printers (that
would require to pass flag_checking to libcpp just for this single case).
2. Code which fills memory in the pools with some predefined patterns in
deallocation methods (this would add some overhead to each deallocation), though
I have not measured performance impact yet.
3. Generators and generated code.
4. Target-specific code
5. 'struct lra_reg' which has an additional field in checking build
6. Likewise, 'struct moveop_static_params' in insn scheduler and
'cumulative_args_t' in target.h.
7. macro-related code in libcpp (for the same reason)
8. real.c and fwprop.c - I'll profile these and also fix to use flag_checking if
there won't be any measurable overhead.

There are 9 patches:
1. Add flag_checking and CHECKING_P macros
2. Use CHECKING_P in libcpp
3. Ada and Java frontends
4. Fortran frontend
5. Pool allocators
6. Generator programs
7. Most of middle-end (GIMPLE, IPA, RTL) - it can be split further, if needed.
8. Target-specific code
9. C++ frontend - in progress (I will send this part soon).

Some issues related to checking builds:
1. Useless check in graphite: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67842
2. I found a test which fails only on release builds:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58583 (reopened)
3. Another one: gcc.c-torture/compile/pr52073.c which is, I guess, caused by
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67816 (the backtrace is the same,
at least).

Each patch (when applied on top of all the previous ones) compiles in both
checking and release builds. The combined patch passes bootstrap and regression
tests in checking an release builds (apart from 2 issues mentioned above) on
x86_64-linux. I'll also run it through config-list.mk.

-- 
Regards,
    Mikhail Maltsev


gcc/ChangeLog:

2015-10-05  Mikhail Maltsev  <maltsevm@gmail.com>

	* common.opt: Add flag_checking.
	* system.h (CHECKING_P): Define.

libcpp/ChangeLog:

2015-10-05  Mikhail Maltsev  <maltsevm@gmail.com>

	* system.h (CHECKING_P, gcc_checking_assert): Define.

>From 8096ea4714b3b7a96b414a70fd0de34e5e5a707a Mon Sep 17 00:00:00 2001
From: Mikhail Maltsev <maltsevm@gmail.com>
Date: Sun, 20 Sep 2015 04:30:42 +0300
Subject: [PATCH 1/9] Prerequisites for ENABLE_CHECKING conversion

Define CHECKING_P macros. Add flag_checking.
Define gcc_checking_assert in libcpp
---
 gcc/common.opt  | 5 +++++
 gcc/system.h    | 3 +++
 libcpp/system.h | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/gcc/common.opt b/gcc/common.opt
index b0f70fb..5060208 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -46,6 +46,11 @@ int optimize_fast
 Variable
 bool in_lto_p = false
 
+; Enable additional checks of internal state consistency, which may slow
+; the compiler down.
+Variable
+bool flag_checking = CHECKING_P
+
 ; 0 means straightforward implementation of complex divide acceptable.
 ; 1 means wide ranges of inputs must work for complex divide.
 ; 2 means C99-like requirements for complex multiply and divide.
diff --git a/gcc/system.h b/gcc/system.h
index f1694b9..dc3b96d 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -716,8 +716,11 @@ extern void fancy_abort (const char *, int, const char *) ATTRIBUTE_NORETURN;
 
 #ifdef ENABLE_CHECKING
 #define gcc_checking_assert(EXPR) gcc_assert (EXPR)
+#define CHECKING_P 1
 #else
+/* N.B.: in release build EXPR is not evaluated.  */
 #define gcc_checking_assert(EXPR) ((void)(0 && (EXPR)))
+#define CHECKING_P 0
 #endif
 
 /* Use gcc_unreachable() to mark unreachable locations (like an
diff --git a/libcpp/system.h b/libcpp/system.h
index a2e8c26..e070bc9 100644
--- a/libcpp/system.h
+++ b/libcpp/system.h
@@ -391,6 +391,14 @@ extern void abort (void);
 #define __builtin_expect(a, b) (a)
 #endif
 
+#ifdef ENABLE_CHECKING
+#define gcc_checking_assert(EXPR) gcc_assert (EXPR)
+#define CHECKING_P 1
+#else
+#define gcc_checking_assert(EXPR) ((void)(0 && (EXPR)))
+#define CHECKING_P 0
+#endif
+
 /* Provide a fake boolean type.  We make no attempt to use the
    C99 _Bool, as it may not be available in the bootstrap compiler,
    and even if it is, it is liable to be buggy.  
-- 
2.1.4