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Re: [patch] Avoid generating warnings for -O2 -Wunreachable-code
2009/11/5 Richard Guenther <richard.guenther@gmail.com>:
>
> The patch should retain -Wunreachable-code as a no-op
> for backward compatibility. ?And it needs a changelog ;)
>
> The patch is ok to apply in a week if nobody raises serious objections.
>
> Thanks,
> Richard.
>
I have modified the patch to retain the option -Wunreachable-code as a
no-op. The patch was tested on my x86 platform.
Is it OK?
Best regards,
Eric
2009-11-06 Eric Fisher <joefoxreal@gmail.com>
* doc/invoke.texi: Remove the documentation about option
-Wunreachable-code.
* testsuite/gcc.dg/Wunreachable-1.c: Remove the testcase of
-Wunreachable-code.
* testsuite/gcc.dg/Wunreachable-2.c: Same to above
* testsuite/gcc.dg/Wunreachable-3.c: Same to above
* testsuite/gcc.dg/Wunreachable-4.c: Same to above
* testsuite/gcc.dg/Wunreachable-5.c: Same to above
* testsuite/gcc.dg/Wunreachable-6.c: Same to above
* testsuite/gcc.dg/Wunreachable-7.c: Same to above
* testsuite/gcc.dg/Wunreachable-8.c: Same to above
* testsuite/gcc.dg/20041231-1.c: Same to above
* testsuite/gcc.dg/pr12603.c: Remove -Wunreachable-code from dg-options
* gcc/common.opt: Change the help string of -Wunreachable-code
to indicate no more support.
* gcc/tree-cfg.c: Remove the implementation of -Wunreachable-code.
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 153929)
+++ doc/invoke.texi (working copy)
@@ -259,7 +259,7 @@ Objective-C and Objective-C++ Dialects}.
-Wstrict-overflow -Wstrict-overflow=@var{n} @gol
-Wswitch -Wswitch-default -Wswitch-enum -Wsync-nand @gol
-Wsystem-headers -Wtrigraphs -Wtype-limits -Wundef -Wuninitialized @gol
--Wunknown-pragmas -Wno-pragmas -Wunreachable-code @gol
+-Wunknown-pragmas -Wno-pragmas @gol
-Wunsuffixed-float-constants -Wunused -Wunused-function @gol
-Wunused-label -Wunused-parameter -Wno-unused-result -Wunused-value
-Wunused-variable @gol
-Wvariadic-macros -Wvla @gol
@@ -4188,29 +4188,6 @@ cases where multiple declaration is vali
@opindex Wno-nested-externs
Warn if an @code{extern} declaration is encountered within a function.
-@item -Wunreachable-code
-@opindex Wunreachable-code
-@opindex Wno-unreachable-code
-Warn if the compiler detects that code will never be executed.
-
-This option is intended to warn when the compiler detects that at
-least a whole line of source code will never be executed, because
-some condition is never satisfied or because it is after a
-procedure that never returns.
-
-It is possible for this option to produce a warning even though there
-are circumstances under which part of the affected line can be executed,
-so care should be taken when removing apparently-unreachable code.
-
-For instance, when a function is inlined, a warning may mean that the
-line is unreachable in only one inlined copy of the function.
-
-This option is not made part of @option{-Wall} because in a debugging
-version of a program there is often substantial code which checks
-correct functioning of the program and is, hopefully, unreachable
-because the program does work. Another common use of unreachable
-code is to provide behavior which is selectable at compile-time.
-
@item -Winline
@opindex Winline
@opindex Wno-inline
Index: testsuite/gcc.dg/Wunreachable-1.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-1.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-1.c (working copy)
@@ -1,24 +0,0 @@
-/* { dg-do compile } */
-/* { dg-options "-O2 -Wunreachable-code" } */
-
-extern void foo (void);
-extern void baz (void);
-
-void bar (int i)
-{
- if (i < 2)
- {
- baz ();
- return;
- }
- else
- {
- if (i >= 4 && i <= 5)
- foo ();
- return;
- }
-
- baz (); /* { dg-warning "will never be executed" "" } */
- baz ();
- baz ();
-}
Index: testsuite/gcc.dg/Wunreachable-5.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-5.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-5.c (working copy)
@@ -1,17 +0,0 @@
-/* PR c/10175 */
-
-/* { dg-do compile } */
-/* { dg-options "-Wunreachable-code" } */
-
-int value;
-
-int main(void)
-{
- if (0)
- value = 0; /* { dg-warning "will never be executed" "" } */
- else
- value = 1;
-
- return 0;
-}
-
Index: testsuite/gcc.dg/Wunreachable-2.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-2.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-2.c (working copy)
@@ -1,19 +0,0 @@
-/* { dg-do compile } */
-/* { dg-options "-O2 -Wunreachable-code" } */
-
-extern int foo (const char *);
-extern void baz (void);
-const char *a[] = { "one", "two" };
-
-void bar (void)
-{
- int i;
-
- for (i = 0; i < 2; i++) /* { dg-bogus "will never be executed" ""
{ xfail *-*-* } } */
- if (! foo (a[i])) /* { dg-bogus "will never be executed" "" {
xfail *-*-* } } */
- return;
-
- baz (); /* { dg-bogus "will never be executed" } */
- baz ();
- baz ();
-}
Index: testsuite/gcc.dg/Wunreachable-6.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-6.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-6.c (working copy)
@@ -1,21 +0,0 @@
-/* PR c/11370 */
-/* { dg-do compile } */
-/* { dg-options "-Wunreachable-code" } */
-
-extern int printf (const char *, ...);
-extern void exit (int);
-
-int main(int argc, char *argv[])
-{
- if (argc != 1)
- exit(1);
-
- {
- int ix; /* { dg-bogus "will never be executed" } */
- ix = printf("hello\n");
- printf("%d\n", ix);
- }
-
- return 0;
-}
-
Index: testsuite/gcc.dg/pr12603.c
===================================================================
--- testsuite/gcc.dg/pr12603.c (revision 153932)
+++ testsuite/gcc.dg/pr12603.c (working copy)
@@ -1,6 +1,6 @@
/* PR 12603: No return statement warning on function that never
returns with -O3. */
/* { dg-do compile } */
-/* { dg-options "-O3 -Wall -Wextra -Wreturn-type -Wunreachable-code" } */
+/* { dg-options "-O3 -Wall -Wextra -Wreturn-type" } */
int
this_function_never_returns ()
{
Index: testsuite/gcc.dg/Wunreachable-3.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-3.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-3.c (working copy)
@@ -1,17 +0,0 @@
-/* PR c/10175 */
-/* { dg-do compile } */
-/* { dg-options "-Wunreachable-code" } */
-
-int i,j;
-int main(void)
-{
- if (0) {
- i = 0; /* { dg-warning "will never be executed" "" } */
- j = 0;
- } else {
- i = 1;
- j = 1;
- }
-
- return 0;
-}
Index: testsuite/gcc.dg/Wunreachable-7.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-7.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-7.c (working copy)
@@ -1,21 +0,0 @@
-/* PR c/11370 */
-/* { dg-do compile } */
-/* { dg-options "-O2 -Wunreachable-code" } */
-
-extern int printf (const char *, ...);
-extern void exit (int);
-
-int main(int argc, char *argv[])
-{
- if (argc != 1)
- exit(1);
-
- {
- int ix; /* { dg-bogus "will never be executed" } */
- ix = printf("hello\n");
- printf("%d\n", ix);
- }
-
- return 0;
-}
-
Index: testsuite/gcc.dg/20041231-1.c
===================================================================
--- testsuite/gcc.dg/20041231-1.c (revision 153929)
+++ testsuite/gcc.dg/20041231-1.c (working copy)
@@ -1,15 +0,0 @@
-/* PR17544 Incorrect -Wunreachable-code warning
- Origin: Giovanni Bajo
-
- In C99 we append a "return 0;" when finishing a function, but it was
- not given a source location. The gimplifier thinks a return statement
- needs a locus so it would add one, making the compiler generated code
- visible to the unreachable code warning. */
-
-/* { dg-do compile } */
-/* { dg-options "-std=c99 -O -Wunreachable-code" } */
-
-int main (void) // 1
-{ // 2
- return 0; // 3
-} // 4
Index: testsuite/gcc.dg/Wunreachable-4.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-4.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-4.c (working copy)
@@ -1,12 +0,0 @@
-/* PR middle-end/10336 */
-/* { dg-options "-Wunreachable-code" } */
-
-void foo(int i)
-{
- switch(i) {
- case 0:
- break;
- case 1:
- break;
- }
-}
Index: testsuite/gcc.dg/Wunreachable-8.c
===================================================================
--- testsuite/gcc.dg/Wunreachable-8.c (revision 153929)
+++ testsuite/gcc.dg/Wunreachable-8.c (working copy)
@@ -1,20 +0,0 @@
-/* { dg-do compile } */
-/* { dg-options "-O2 -Wunreachable-code" } */
-float Factorial(float X)
-{
- float val = 1.0;
- int k,j;
- for (k=1; k < 5; k++) /* { dg-bogus "will never be executed" "" {
xfail *-*-* } } */
- {
- val += 1.0; /* { dg-bogus "will never be executed" "" { xfail
*-*-* } } */
- }
- return (val); /* { dg-bogus "will never be executed" } */
-}
-
-int main (void)
-{
- float result;
- result=Factorial(2.1);
- return (0);
-}
-
Index: common.opt
===================================================================
--- common.opt (revision 153929)
+++ common.opt (working copy)
@@ -202,7 +202,7 @@ Warn about uninitialized automatic varia
Wunreachable-code
Common Var(warn_notreached) Warning
-Warn about code that will never be executed
+This option is not supported and just retains here for backword compatibility.
Wunused
Common Var(warn_unused) Init(0) Warning
Index: tree-cfg.c
===================================================================
--- tree-cfg.c (revision 153929)
+++ tree-cfg.c (working copy)
@@ -1760,7 +1760,6 @@ static void
remove_bb (basic_block bb)
{
gimple_stmt_iterator i;
- source_location loc = UNKNOWN_LOCATION;
if (dump_file)
{
@@ -1830,24 +1829,9 @@ remove_bb (basic_block bb)
i = gsi_last_bb (bb);
else
gsi_prev (&i);
-
- /* Don't warn for removed gotos. Gotos are often removed due to
- jump threading, thus resulting in bogus warnings. Not great,
- since this way we lose warnings for gotos in the original
- program that are indeed unreachable. */
- if (gimple_code (stmt) != GIMPLE_GOTO
- && gimple_has_location (stmt))
- loc = gimple_location (stmt);
}
}
- /* If requested, give a warning that the first statement in the
- block is unreachable. We walk statements backwards in the
- loop above, so the last statement we process is the first statement
- in the block. */
- if (loc > BUILTINS_LOCATION && LOCATION_LINE (loc) > 0)
- warning_at (loc, OPT_Wunreachable_code, "will never be executed");
-
remove_phi_nodes_and_edges_for_unreachable_block (bb);
bb->il.gimple = NULL;
}
=== gcc Summary ===
# of expected passes 60290
# of unexpected failures 7
# of unexpected successes 7
# of expected failures 201
# of unresolved testcases 4
# of unsupported tests 610
FAIL: gcc.dg/pr34668-1.c (internal compiler error)
FAIL: gcc.dg/pr34668-1.c (test for excess errors)
FAIL: gcc.dg/struct/wo_prof_double_malloc.c (internal compiler error)
FAIL: gcc.dg/struct/wo_prof_double_malloc.c (test for excess errors)
FAIL: gcc.target/i386/avx-vmovntdq-256-1.c (test for excess errors)
FAIL: gcc.target/i386/avx-vmovntpd-256-1.c (test for excess errors)
FAIL: gcc.target/i386/avx-vmovntps-256-1.c (test for excess errors)
XPASS: gcc.dg/Warray-bounds.c (test for warnings, line 59)
XPASS: gcc.dg/Warray-bounds.c (test for warnings, line 65)
XPASS: gcc.dg/guality/example.c -O0 execution test
XPASS: gcc.dg/guality/pr41353-1.c -O0 line 28 j == 28 + 37
XPASS: gcc.dg/guality/pr41447-1.c -O0 execution test
XPASS: gcc.dg/guality/pr41616-1.c -O0 execution test
XPASS: gcc.dg/struct/wo_prof_array_through_pointer.c scan-ipa-dump
ipa_struct_reorg "Number of structures to transform is 1"