$ cpuctl identify 0                                                                                                      
Cannot bind to target CPU.  Output may not accurately describe the target.
Run as root to allow binding.

cpu0: highest basic info 0000000d
cpu0: highest extended info 80000008
cpu0: "Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz"
cpu0: Intel Xeon E3-1200v2 and 3rd gen core, Ivy Bridge (686-class), 3392.53 MHz
cpu0: family 0x6 model 0x3a stepping 0x9 (id 0x306a9)
cpu0: features 0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE>
cpu0: features 0xbfebfbff<MCA,CMOV,PAT,PSE36,CLFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2>
cpu0: features 0xbfebfbff<SS,HTT,TM,SBF>
cpu0: features1 0x7fbae3ff<SSE3,PCLMULQDQ,DTES64,MONITOR,DS-CPL,VMX,SMX,EST>
cpu0: features1 0x7fbae3ff<TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE41,SSE42,X2APIC>
cpu0: features1 0x7fbae3ff<POPCNT,DEADLINE,AES,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
cpu0: features2 0x28100800<SYSCALL/SYSRET,XD,RDTSCP,EM64T>
cpu0: features3 0x1<LAHF>
cpu0: features5 0x281<FSGSBASE,SMEP,ERMS>
cpu0: xsave features 0x7<x87,SSE,AVX>
cpu0: xsave instructions 0x1<XSAVEOPT>
cpu0: xsave area size: current 832, maximum 832, xgetbv enabled
cpu0: enabled xsave 0x7<x87,SSE,AVX>
cpu0: I-cache 32KB 64B/line 8-way, D-cache 32KB 64B/line 8-way
cpu0: L2 cache 256KB 64B/line 8-way
cpu0: L3 cache 8MB 64B/line 16-way
cpu0: 64B prefetching
cpu0: ITLB 64 4KB entries 4-way, 2M/4M: 8 entries
cpu0: DTLB 64 4KB entries 4-way, 2M/4M: 32 entries (L0)
cpu0: L2 STLB 512 4KB entries 4-way
cpu0: Initial APIC ID 6
cpu0: Cluster/Package ID 0
cpu0: Core ID 3
cpu0: SMT ID 0
cpu0: MONITOR/MWAIT extensions 0x3<EMX,IBE>
cpu0: monitor-line size 64
cpu0: C1 substates 2
cpu0: C2 substates 1
cpu0: C3 substates 1
cpu0: DSPM-eax 0x77<DTS,IDA,ARAT,PLN,ECMD,PTM>
cpu0: DSPM-ecx 0x9<HWF,EPB>
cpu0: SEF highest subleaf 00000000
cpu0: Perfmon-eax 0x7300403<VERSION=0x3,GPCounter=0x4,GPBitwidth=0x30>
cpu0: Perfmon-eax 0x7300403<Vectorlen=0x7>
cpu0: Perfmon-edx 0x603<FixedFunc=0x3,FFBitwidth=0x30>
cpu0: microcode version 0x15, platform ID 1

$ uname -a
NetBSD chieftec 8.99.37 NetBSD 8.99.37 (GENERIC) #3: Thu Apr 25 03:33:44 CEST 2019  root@chieftec:/public/netbsd-root/sys/arch/amd64/compile/GENERIC amd64

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/lto-wrapper
Target: x86_64--netbsd
Configured with: /usr/src/tools/gcc/../../external/gpl3/gcc/dist/configure --target=x86_64--netbsd --enable-long-long --enable-threads --with-bugurl=http://www.NetBSD.org/Misc/send-pr.html --with-pkgversion='NetBSD nb3 20190319' --with-system-zlib --without-isl --enable-__cxa_atexit --enable-libstdcxx-time=rt --enable-libstdcxx-threads --with-diagnostics-color=auto-if-env --with-tune=nocona --with-default-libstdcxx-abi=new --with-mpc-lib=/var/obj/mknative/amd64-x86_64/usr/src/external/lgpl3/mpc/lib/libmpc --with-mpfr-lib=/var/obj/mknative/amd64-x86_64/usr/src/external/lgpl3/mpfr/lib/libmpfr --with-gmp-lib=/var/obj/mknative/amd64-x86_64/usr/src/external/lgpl3/gmp/lib/libgmp --with-mpc-include=/usr/src/external/lgpl3/mpc/dist/src --with-mpfr-include=/usr/src/external/lgpl3/mpfr/dist/src --with-gmp-include=/usr/src/external/lgpl3/gmp/lib/libgmp/arch/x86_64 --enable-tls --disable-multilib --disable-libstdcxx-pch --build=x86_64--netbsd --host=x86_64--netbsd --with-sysroot=/var/obj/mknative/amd64-x86_64/usr/src/destdir.amd64
Thread model: posix
gcc version 7.4.0 (nb3 20190319) 

# Test 1

$ cat fileno.c
#include <stdio.h> // patched
#include <stdlib.h>

int
main(int argc, char **argv)
{
	size_t i, j, k;
	volatile int a;

	for (i = 0; i < 1000; i++) {
		for (j = 0; j < 1000; j++) {
			for (k = 0; k < 1000; k++) {
				a = fileno(stdout);
				if (a == -1)
					return EXIT_FAILURE;
			}
		}
	}

	return EXIT_SUCCESS;
}
$ gcc fileno.c

# Test 2

$ cat fileno.c
#include <stdio.h> // patched
#include <stdlib.h>

int
main(int argc, char **argv)
{
	size_t i, j, k;
	volatile int a;

	for (i = 0; i < 1000; i++) {
		for (j = 0; j < 1000; j++) {
			for (k = 0; k < 1000; k++) {
				a = fileno_unlocked(stdout);
				if (a == -1)
					return EXIT_FAILURE;
			}
		}
	}

	return EXIT_SUCCESS;
}
$ gcc fileno.c

# Test 3

$ cat fileno.c
#include <stdio.h> // patched
#include <stdlib.h>

int
main(int argc, char **argv)
{
	size_t i, j, k;
	volatile int a;

	for (i = 0; i < 1000; i++) {
		for (j = 0; j < 1000; j++) {
			for (k = 0; k < 1000; k++) {
				a = fileno(stdout);
				if (a == -1)
					return EXIT_FAILURE;
			}
		}
	}

	return EXIT_SUCCESS;
}
$ gcc fileno.c -pthread

# Test 4

$ cat fileno.c
#include <stdio.h> // original
#include <stdlib.h>

int
main(int argc, char **argv)
{
	size_t i, j, k;
	volatile int a;

	for (i = 0; i < 1000; i++) {
		for (j = 0; j < 1000; j++) {
			for (k = 0; k < 1000; k++) {
				a = fileno(stdout);
				if (a == -1)
					return EXIT_FAILURE;
			}
		}
	}

	return EXIT_SUCCESS;
}
$ gcc fileno.c