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	27	#define __pure __attribute__((pure))
28	28	#endif
29	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	30	#ifndef __packed
43	31	#define __packed __attribute__((packed))
44	32	#endif

tools/include/linux/compiler.h+0−3

@@ -47,9 +47,6 @@ · 46 unmodified lines
47	47	#ifndef noinline
48	48	#define noinline
49	49	#endif
50		−#ifndef __no_tail_call
51		−#define __no_tail_call
52		−#endif
53	50
54	51	/* Are two types/vars the same type (ignoring qualifiers)? */
55	52	#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	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	100	struct perf_sample sample;
101	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	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	131	/* Any possible value should be 'thread' */
132	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	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	150	struct thread *array[2] = {thread, thread};
151	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	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	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	174	return test_dwarf_unwind__krava_2(thread);
175	175	}

perf tools: Remove broken __no_tail_call attribute

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