perf annotate: Check for fused instructions

Macro fusion merges two instructions to a single micro-op. Intel core
platform performs this hardware optimization under limited
circumstances.

For example, CMP + JCC can be "fused" and executed /retired together.
While with sampling this can result in the sample sometimes being on the
JCC and sometimes on the CMP. So for the fused instruction pair, they
could be considered together.

On Nehalem, fused instruction pairs:

cmp/test + jcc.

On other new CPU:

cmp/test/add/sub/and/inc/dec + jcc.

This patch adds an x86-specific function which checks if 2 instructions
are in a "fused" pair. For non-x86 arch, the function is just NULL.

Changelog:

v4: Move the CPU model checking to symbol__disassemble and save the CPU
family/model in arch structure.

It avoids checking every time when jump arrow printed.

v3: Add checking for Nehalem (CMP, TEST). For other newer Intel CPUs
just check it by default (CMP, TEST, ADD, SUB, AND, INC, DEC).

v2: Remove the original weak function. Arnaldo points out that doing it
as a weak function that will be overridden by the host arch doesn't
work. So now it's implemented as an arch-specific function.

Committer fix:

Do not access evsel->evlist->env->cpuid, ->env can be null, introduce
perf_evsel__env_cpuid(), just like perf_evsel__env_arch(), also used in
this function call.

The original patch was segfaulting 'perf top' + annotation.

But this essentially disables this fused instructions augmentation in
'perf top', the right thing is to get the cpuid from the running kernel,
left for a later patch tho.

Signed-off-by: Yao Jin <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/arch/x86/annotate/instructions.c

···
 	{ .name = "xbeginq",	.ops = &jump_ops, },
 	{ .name = "retq",	.ops = &ret_ops,  },
 };
+
+static bool x86__ins_is_fused(struct arch *arch, const char *ins1,
+			      const char *ins2)
+{
+	if (arch->family != 6 || arch->model < 0x1e || strstr(ins2, "jmp"))
+		return false;
+
+	if (arch->model == 0x1e) {
+		/* Nehalem */
+		if ((strstr(ins1, "cmp") && !strstr(ins1, "xchg")) ||
+		     strstr(ins1, "test")) {
+			return true;
+		}
+	} else {
+		/* Newer platform */
+		if ((strstr(ins1, "cmp") && !strstr(ins1, "xchg")) ||
+		     strstr(ins1, "test") ||
+		     strstr(ins1, "add") ||
+		     strstr(ins1, "sub") ||
+		     strstr(ins1, "and") ||
+		     strstr(ins1, "inc") ||
+		     strstr(ins1, "dec")) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static int x86__cpuid_parse(struct arch *arch, char *cpuid)
+{
+	unsigned int family, model, stepping;
+	int ret;
+
+	/*
+	 * cpuid = "GenuineIntel,family,model,stepping"
+	 */
+	ret = sscanf(cpuid, "%*[^,],%u,%u,%u", &family, &model, &stepping);
+	if (ret == 3) {
+		arch->family = family;
+		arch->model = model;
+		return 0;
+	}
+
+	return -1;
+}

tools/perf/builtin-top.c

···
 		return err;
 	}
 
-	err = symbol__disassemble(sym, map, NULL, 0, NULL);
+	err = symbol__disassemble(sym, map, NULL, 0, NULL, NULL);
 	if (err == 0) {
 out_assign:
 		top->sym_filter_entry = he;

tools/perf/ui/browsers/annotate.c

···
 #include "../../util/symbol.h"
 #include "../../util/evsel.h"
 #include "../../util/config.h"
+#include "../../util/evlist.h"
 #include <inttypes.h>
 #include <pthread.h>
 #include <linux/kernel.h>
···
 	}
 
 	err = symbol__disassemble(sym, map, perf_evsel__env_arch(evsel),
-				  sizeof_bdl, &browser.arch);
+				  sizeof_bdl, &browser.arch,
+				  perf_evsel__env_cpuid(evsel));
 	if (err) {
 		char msg[BUFSIZ];
 		symbol__strerror_disassemble(sym, map, err, msg, sizeof(msg));

tools/perf/ui/gtk/annotate.c

···
 		return -1;
 
 	err = symbol__disassemble(sym, map, perf_evsel__env_arch(evsel),
-				  0, NULL);
+				  0, NULL, NULL);
 	if (err) {
 		char msg[BUFSIZ];
 		symbol__strerror_disassemble(sym, map, err, msg, sizeof(msg));

tools/perf/util/annotate.c

···
 	bool		sorted_instructions;
 	bool		initialized;
 	void		*priv;
+	unsigned int	model;
+	unsigned int	family;
 	int		(*init)(struct arch *arch);
+	bool		(*ins_is_fused)(struct arch *arch, const char *ins1,
+					const char *ins2);
+	int		(*cpuid_parse)(struct arch *arch, char *cpuid);
 	struct		{
 		char comment_char;
 		char skip_functions_char;
···
 		.name = "x86",
 		.instructions = x86__instructions,
 		.nr_instructions = ARRAY_SIZE(x86__instructions),
+		.ins_is_fused = x86__ins_is_fused,
+		.cpuid_parse = x86__cpuid_parse,
 		.objdump =  {
 			.comment_char = '#',
 		},
···
 		return ins->ops->scnprintf(ins, bf, size, ops);
 
 	return ins__raw_scnprintf(ins, bf, size, ops);
+}
+
+bool ins__is_fused(struct arch *arch, const char *ins1, const char *ins2)
+{
+	if (!arch || !arch->ins_is_fused)
+		return false;
+
+	return arch->ins_is_fused(arch, ins1, ins2);
 }
 
 static int call__parse(struct arch *arch, struct ins_operands *ops, struct map *map)
···
 
 int symbol__disassemble(struct symbol *sym, struct map *map,
 			const char *arch_name, size_t privsize,
-			struct arch **parch)
+			struct arch **parch, char *cpuid)
 {
 	struct dso *dso = map->dso;
 	char command[PATH_MAX * 2];
···
 			return err;
 		}
 	}
+
+	if (arch->cpuid_parse && cpuid)
+		arch->cpuid_parse(arch, cpuid);
 
 	pr_debug("%s: filename=%s, sym=%s, start=%#" PRIx64 ", end=%#" PRIx64 "\n", __func__,
 		 symfs_filename, sym->name, map->unmap_ip(map, sym->start),
···
 	u64 len;
 
 	if (symbol__disassemble(sym, map, perf_evsel__env_arch(evsel),
-				0, NULL) < 0)
+				0, NULL, NULL) < 0)
 		return -1;
 
 	len = symbol__size(sym);

tools/perf/util/annotate.h

···
 bool ins__is_call(const struct ins *ins);
 bool ins__is_ret(const struct ins *ins);
 int ins__scnprintf(struct ins *ins, char *bf, size_t size, struct ins_operands *ops);
+bool ins__is_fused(struct arch *arch, const char *ins1, const char *ins2);
 
 struct annotation;
 
···
 
 int symbol__disassemble(struct symbol *sym, struct map *map,
 			const char *arch_name, size_t privsize,
-			struct arch **parch);
+			struct arch **parch, char *cpuid);
 
 enum symbol_disassemble_errno {
 	SYMBOL_ANNOTATE_ERRNO__SUCCESS		= 0,

tools/perf/util/evsel.c

···
 		return evsel->evlist->env->arch;
 	return NULL;
 }
+
+char *perf_evsel__env_cpuid(struct perf_evsel *evsel)
+{
+	if (evsel && evsel->evlist && evsel->evlist->env)
+		return evsel->evlist->env->cpuid;
+	return NULL;
+}

tools/perf/util/evsel.h

···
 			     attr__fprintf_f attr__fprintf, void *priv);
 
 char *perf_evsel__env_arch(struct perf_evsel *evsel);
+char *perf_evsel__env_cpuid(struct perf_evsel *evsel);
 
 #endif /* __PERF_EVSEL_H */