benchmark/test/clobber_memory_assembly_test.cc
Eric 7b03df7ff7
Add tests to verify assembler output -- Fix DoNotOptimize. (#530)
* Add tests to verify assembler output -- Fix DoNotOptimize.

For things like `DoNotOptimize`, `ClobberMemory`, and even `KeepRunning()`,
it is important exactly what assembly they generate. However, we currently
have no way to test this. Instead it must be manually validated every
time a change occurs -- including a change in compiler version.

This patch attempts to introduce a way to test the assembled output automatically.
It's mirrors how LLVM verifies compiler output, and it uses LLVM FileCheck to run
the tests in a similar way.

The tests function by generating the assembly for a test in CMake, and then
using FileCheck to verify the // CHECK lines in the source file are found
in the generated assembly.

Currently, the tests only run on 64-bit x86 systems under GCC and Clang,
and when FileCheck is found on the system.

Additionally, this patch tries to improve the code gen from DoNotOptimize.
This should probably be a separate change, but I needed something to test.

* Disable assembly tests on Bazel for now

* Link FIXME to github issue

* Fix Tests on OS X

* fix strip_asm.py to work on both Linux and OS X like targets
2018-03-23 16:10:47 -06:00

65 lines
1.3 KiB
C++

#include <benchmark/benchmark.h>
#ifdef __clang__
#pragma clang diagnostic ignored "-Wreturn-type"
#endif
extern "C" {
extern int ExternInt;
extern int ExternInt2;
extern int ExternInt3;
}
// CHECK-LABEL: test_basic:
extern "C" void test_basic() {
int x;
benchmark::DoNotOptimize(&x);
x = 101;
benchmark::ClobberMemory();
// CHECK: leaq [[DEST:[^,]+]], %rax
// CHECK: movl $101, [[DEST]]
// CHECK: ret
}
// CHECK-LABEL: test_redundant_store:
extern "C" void test_redundant_store() {
ExternInt = 3;
benchmark::ClobberMemory();
ExternInt = 51;
// CHECK-DAG: ExternInt
// CHECK-DAG: movl $3
// CHECK: movl $51
}
// CHECK-LABEL: test_redundant_read:
extern "C" void test_redundant_read() {
int x;
benchmark::DoNotOptimize(&x);
x = ExternInt;
benchmark::ClobberMemory();
x = ExternInt2;
// CHECK: leaq [[DEST:[^,]+]], %rax
// CHECK: ExternInt(%rip)
// CHECK: movl %eax, [[DEST]]
// CHECK-NOT: ExternInt2
// CHECK: ret
}
// CHECK-LABEL: test_redundant_read2:
extern "C" void test_redundant_read2() {
int x;
benchmark::DoNotOptimize(&x);
x = ExternInt;
benchmark::ClobberMemory();
x = ExternInt2;
benchmark::ClobberMemory();
// CHECK: leaq [[DEST:[^,]+]], %rax
// CHECK: ExternInt(%rip)
// CHECK: movl %eax, [[DEST]]
// CHECK: ExternInt2(%rip)
// CHECK: movl %eax, [[DEST]]
// CHECK: ret
}