perf tools: Remove broken __no_tail_call attribute

The GCC specific __attribute__((optimize)) attribute does not what is commonly expected and is explicitly recommended against using in production code by the GCC people. Unlike what is often expected, it doesn't add to the optimization flags, but it fully replaces them, loosing any and all optimization flags provided by the compiler commandline. The only guaranteed upon means of inhibiting tail-calls is by placing a volatile asm with side-effects after the call such that the tail-call simply cannot be done. Given the original commit wasn't specific on which calls were the problem, this removal might re-introduce the problem, which can then be re-analyzed and cured properly.

Peter Zijlstra committed 6 years ago

Commit 9ae1e991 parent 0dfbe4c3 files · +5 −20Browse files

Unified · Split

3 files

tools/include/linux/compiler-gcc.h +0 −12
tools/include/linux/compiler.h +0 −3
tools/perf/tests/dwarf-unwind.c +5 −5

tools/include/linux/compiler-gcc.h+0−12

@@ -27,18 +27,6 @@ · 26 unmodified lines
27	#define __pure __attribute__((pure))	27	#define __pure __attribute__((pure))
28	#endif	28	#endif
29	#define noinline __attribute__((noinline))	29	#define noinline __attribute__((noinline))
30	#ifdef __has_attribute
31	#if __has_attribute(disable_tail_calls)
32	#define __no_tail_call __attribute__((disable_tail_calls))
33	#endif
34	#endif
35	#ifndef __no_tail_call
36	#if GCC_VERSION > 40201
37	#define __no_tail_call __attribute__((optimize("no-optimize-sibling-calls")))
38	#else
39	#define __no_tail_call
40	#endif
41	#endif
42	#ifndef __packed	30	#ifndef __packed
43	#define __packed __attribute__((packed))	31	#define __packed __attribute__((packed))
44	#endif	32	#endif

tools/include/linux/compiler.h+0−3

 #ifndef noinline
 #define noinline
 #endif
-#ifndef __no_tail_call
-#define __no_tail_call
-#endif
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #ifndef __same_type

tools/perf/tests/dwarf-unwind.c+5−5

@@ -95,7 +95,7 @@ static int unwind_entry(struct unwind_entry entry, void arg) · 94 unmodified lines
95	return strcmp((const char *) symbol, funcs[idx]);	95	return strcmp((const char *) symbol, funcs[idx]);
96	}	96	}
97		97
98	__no_tail_call noinline int test_dwarf_unwind__thread(struct thread *thread)	98	noinline int test_dwarf_unwind__thread(struct thread *thread)
99	{	99	{
100	struct perf_sample sample;	100	struct perf_sample sample;
101	unsigned long cnt = 0;	101	unsigned long cnt = 0;
@@ -126,7 +126,7 @@ __no_tail_call noinline int test_dwarf_unwind__thread(struct thread *thread) · 24 unmodified lines
126		126
127	static int global_unwind_retval = -INT_MAX;	127	static int global_unwind_retval = -INT_MAX;
128		128
129	__no_tail_call noinline int test_dwarf_unwind__compare(void p1, void p2)	129	noinline int test_dwarf_unwind__compare(void p1, void p2)
130	{	130	{
131	/* Any possible value should be 'thread' */	131	/* Any possible value should be 'thread' */
132	struct thread thread = (struct thread **)p1;	132	struct thread thread = (struct thread **)p1;
@@ -145,7 +145,7 @@ __no_tail_call noinline int test_dwarf_unwind__compare(void p1, void p2) · 12 unmodified lines
145	return p1 - p2;	145	return p1 - p2;
146	}	146	}
147		147
148	__no_tail_call noinline int test_dwarf_unwind__krava_3(struct thread *thread)	148	noinline int test_dwarf_unwind__krava_3(struct thread *thread)
149	{	149	{
150	struct thread *array[2] = {thread, thread};	150	struct thread *array[2] = {thread, thread};
151	void *fp = &bsearch;	151	void *fp = &bsearch;
@@ -164,12 +164,12 @@ __no_tail_call noinline int test_dwarf_unwind__krava_3(struct thread *thread) · 12 unmodified lines
164	return global_unwind_retval;	164	return global_unwind_retval;
165	}	165	}
166		166
167	__no_tail_call noinline int test_dwarf_unwind__krava_2(struct thread *thread)	167	noinline int test_dwarf_unwind__krava_2(struct thread *thread)
168	{	168	{
169	return test_dwarf_unwind__krava_3(thread);	169	return test_dwarf_unwind__krava_3(thread);
170	}	170	}
171		171
172	__no_tail_call noinline int test_dwarf_unwind__krava_1(struct thread *thread)	172	noinline int test_dwarf_unwind__krava_1(struct thread *thread)
173	{	173	{
174	return test_dwarf_unwind__krava_2(thread);	174	return test_dwarf_unwind__krava_2(thread);
175	}	175	}

perf tools: Remove broken __no_tail_call attribute

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