[llvm] 2c9dc7b - Revert "[llvm-exegesis] Add option to check the hardware support for a given feature before benchmarking."
Michael Liao via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 30 20:21:44 PDT 2020
Author: Michael Liao
Date: 2020-09-30T23:15:35-04:00
New Revision: 2c9dc7bbbf514b1ed7bdefacb3213beae5916b3d
URL: https://github.com/llvm/llvm-project/commit/2c9dc7bbbf514b1ed7bdefacb3213beae5916b3d
DIFF: https://github.com/llvm/llvm-project/commit/2c9dc7bbbf514b1ed7bdefacb3213beae5916b3d.diff
LOG: Revert "[llvm-exegesis] Add option to check the hardware support for a given feature before benchmarking."
This reverts commit 4fcd1a8e6528ca42fe656f2745e15d2b7f5de495 as
`llvm/test/tools/llvm-exegesis/X86/lbr/mov-add.s` failed on hosts
without LBR supported if the build has LIBPFM enabled. On that host,
`perf_event_open` fails with `EOPNOTSUPP` on LBR config. That change's
basic assumption
> If this is run on a non-supported hardware, it will produce all zeroes for latency.
could not stand as `perf_event_open` system call will fail if the
underlying hardware really don't have LBR supported.
Added:
Modified:
llvm/test/tools/llvm-exegesis/X86/lbr/lit.local.cfg
llvm/tools/llvm-exegesis/lib/Target.h
llvm/tools/llvm-exegesis/lib/X86/Target.cpp
llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
llvm/tools/llvm-exegesis/lib/X86/X86Counter.h
llvm/tools/llvm-exegesis/llvm-exegesis.cpp
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-exegesis/X86/lbr/lit.local.cfg b/llvm/test/tools/llvm-exegesis/X86/lbr/lit.local.cfg
index 69b08f27c39a..431967c1ec9b 100644
--- a/llvm/test/tools/llvm-exegesis/X86/lbr/lit.local.cfg
+++ b/llvm/test/tools/llvm-exegesis/X86/lbr/lit.local.cfg
@@ -19,9 +19,9 @@ else:
try:
with open(os.devnull, 'w') as quiet:
check_llvm_exegesis_uops_result = subprocess.call(
- [llvm_exegesis_exe, '-mode', 'uops', '-snippets-file', '/dev/null'], stdout=quiet, stderr=quiet)
+ [llvm_exegesis_exe, '-allowed-host-cpu', 'skylake', '-allowed-host-cpu', 'skylake-avx512', '-mode', 'uops', '-snippets-file', '/dev/null'], stdout=quiet, stderr=quiet)
check_llvm_exegesis_latency_result = subprocess.call(
- [llvm_exegesis_exe, '-mode', 'latency', '-snippets-file', '/dev/null'], stdout=quiet, stderr=quiet)
+ [llvm_exegesis_exe, '-allowed-host-cpu', 'skylake', '-allowed-host-cpu', 'skylake-avx512', '-mode', 'latency', '-snippets-file', '/dev/null'], stdout=quiet, stderr=quiet)
except OSError:
print('could not exec llvm-exegesis')
config.unsupported = True
diff --git a/llvm/tools/llvm-exegesis/lib/Target.h b/llvm/tools/llvm-exegesis/lib/Target.h
index 8a5624b42803..70890795426d 100644
--- a/llvm/tools/llvm-exegesis/lib/Target.h
+++ b/llvm/tools/llvm-exegesis/lib/Target.h
@@ -142,11 +142,6 @@ class ExegesisTarget {
return {&Instr};
}
- // Checks hardware and software support for current benchmark mode.
- // Returns an error if the target host does not have support to run the
- // benchmark.
- virtual Error checkFeatureSupport() const { return Error::success(); }
-
// Creates a snippet generator for the given mode.
std::unique_ptr<SnippetGenerator>
createSnippetGenerator(InstructionBenchmark::ModeE Mode,
diff --git a/llvm/tools/llvm-exegesis/lib/X86/Target.cpp b/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
index 270825a8777b..9f045fa11aa2 100644
--- a/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
@@ -674,23 +674,6 @@ class ExegesisX86Target : public ExegesisTarget {
return Arch == Triple::x86_64 || Arch == Triple::x86;
}
- Error checkFeatureSupport() const override {
- // LBR is the only feature we conditionally support now.
- // So if LBR is not requested, then we should be able to run the benchmarks.
- if (LbrSamplingPeriod == 0)
- return Error::success();
-
-#if defined(__linux__) && defined(HAVE_LIBPFM) && \
- defined(LIBPFM_HAS_FIELD_CYCLES)
- // If the kernel supports it, the hardware still may not have it.
- return X86LbrCounter::checkLbrSupport();
-#else
- return llvm::make_error<llvm::StringError>(
- "LBR not supported on this kernel and/or platform",
- llvm::errc::not_supported);
-#endif
- }
-
static const unsigned kUnavailableRegisters[4];
};
diff --git a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
index 25ec4f858675..57b493818aaa 100644
--- a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
+++ b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp
@@ -21,7 +21,6 @@
#endif // HAVE_LIBPFM
#include <atomic>
-#include <chrono>
#include <cstddef>
#include <cstdint>
#include <limits>
@@ -36,8 +35,6 @@
namespace llvm {
namespace exegesis {
-// Number of entries in the LBR.
-static constexpr int kLbrEntries = 16;
static constexpr size_t kBufferPages = 8;
static const size_t kDataBufferSize = kBufferPages * getpagesize();
@@ -73,6 +70,7 @@ static void copyDataBuffer(void *MMappedBuffer, char *Buf, uint64_t Tail,
static llvm::Error parseDataBuffer(const char *DataBuf, size_t DataSize,
const void *From, const void *To,
llvm::SmallVector<int64_t, 4> *CycleArray) {
+ assert(From != nullptr && To != nullptr);
const char *DataPtr = DataBuf;
while (DataPtr < DataBuf + DataSize) {
struct perf_event_header Header;
@@ -151,47 +149,21 @@ void X86LbrCounter::start() {
ioctl(FileDescriptor, PERF_EVENT_IOC_REFRESH, 1024 /* kMaxPollsPerFd */);
}
-llvm::Error X86LbrCounter::checkLbrSupport() {
- // Do a sample read and check if the results contain non-zero values.
-
- X86LbrCounter counter(X86LbrPerfEvent(123));
- counter.start();
-
- // Prevent the compiler from unrolling the loop and get rid of all the
- // branches. We need at least 16 iterations.
- int Sum = 0;
- int V = 1;
-
- volatile int *P = &V;
- auto TimeLimit =
- std::chrono::high_resolution_clock::now() + std::chrono::microseconds(5);
-
- for (int I = 0;
- I < kLbrEntries || std::chrono::high_resolution_clock::now() < TimeLimit;
- ++I) {
- Sum += *P;
- }
-
- counter.stop();
-
- auto ResultOrError = counter.doReadCounter(nullptr, nullptr);
- if (ResultOrError)
- if (!ResultOrError.get().empty())
- // If there is at least one non-zero entry, then LBR is supported.
- for (const int64_t &Value : ResultOrError.get())
- if (Value != 0)
- return Error::success();
-
- return llvm::make_error<llvm::StringError>(
- "LBR format with cycles is not suppported on the host.",
- llvm::errc::not_supported);
-}
-
llvm::Expected<llvm::SmallVector<int64_t, 4>>
X86LbrCounter::readOrError(StringRef FunctionBytes) const {
+ // The max number of time-outs/retries before we give up.
+ static constexpr int kMaxTimeouts = 160;
+
// Disable the event before reading
ioctl(FileDescriptor, PERF_EVENT_IOC_DISABLE, 0);
+ // Parses the LBR buffer and fills CycleArray with the sequence of cycle
+ // counts from the buffer.
+ llvm::SmallVector<int64_t, 4> CycleArray;
+ std::unique_ptr<char[]> DataBuf(new char[kDataBufferSize]);
+ int NumTimeouts = 0;
+ int PollResult = 0;
+
// Find the boundary of the function so that we could filter the LBRs
// to keep only the relevant records.
if (FunctionBytes.empty())
@@ -200,21 +172,6 @@ X86LbrCounter::readOrError(StringRef FunctionBytes) const {
const void *From = reinterpret_cast<const void *>(FunctionBytes.data());
const void *To = reinterpret_cast<const void *>(FunctionBytes.data() +
FunctionBytes.size());
- return doReadCounter(From, To);
-}
-
-llvm::Expected<llvm::SmallVector<int64_t, 4>>
-X86LbrCounter::doReadCounter(const void *From, const void *To) const {
- // The max number of time-outs/retries before we give up.
- static constexpr int kMaxTimeouts = 160;
-
- // Parses the LBR buffer and fills CycleArray with the sequence of cycle
- // counts from the buffer.
- llvm::SmallVector<int64_t, 4> CycleArray;
- auto DataBuf = std::make_unique<char[]>(kDataBufferSize);
- int NumTimeouts = 0;
- int PollResult = 0;
-
while (PollResult <= 0) {
PollResult = pollLbrPerfEvent(FileDescriptor);
if (PollResult > 0)
diff --git a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.h b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.h
index 73e4dc5b990a..94062012917d 100644
--- a/llvm/tools/llvm-exegesis/lib/X86/X86Counter.h
+++ b/llvm/tools/llvm-exegesis/lib/X86/X86Counter.h
@@ -33,8 +33,6 @@ class X86LbrPerfEvent : public pfm::PerfEvent {
class X86LbrCounter : public pfm::Counter {
public:
- static llvm::Error checkLbrSupport();
-
explicit X86LbrCounter(pfm::PerfEvent &&Event);
virtual ~X86LbrCounter();
@@ -45,9 +43,6 @@ class X86LbrCounter : public pfm::Counter {
readOrError(StringRef FunctionBytes) const override;
private:
- llvm::Expected<llvm::SmallVector<int64_t, 4>>
- doReadCounter(const void *From, const void *To) const;
-
void *MMappedBuffer = nullptr;
};
diff --git a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
index bc2f348a7eae..fb3f41e14734 100644
--- a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
+++ b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
@@ -160,6 +160,12 @@ static cl::opt<std::string>
cl::desc(""), cl::cat(AnalysisOptions),
cl::init(""));
+static cl::list<std::string>
+ AllowedHostCpus("allowed-host-cpu",
+ cl::desc("If specified, only run the benchmark if the host "
+ "CPU matches the names"),
+ cl::cat(Options), cl::ZeroOrMore);
+
static cl::opt<bool> AnalysisDisplayUnstableOpcodes(
"analysis-display-unstable-clusters",
cl::desc("if there is more than one benchmark for an opcode, said "
@@ -296,9 +302,12 @@ void benchmarkMain() {
const LLVMState State(CpuName);
- // Preliminary check to ensure features needed for requested
- // benchmark mode are present on target CPU and/or OS.
- ExitOnErr(State.getExegesisTarget().checkFeatureSupport());
+ llvm::StringRef ActualCpu = State.getTargetMachine().getTargetCPU();
+ for (auto Begin = AllowedHostCpus.begin(); Begin != AllowedHostCpus.end();
+ ++Begin) {
+ if (ActualCpu != *Begin)
+ ExitWithError(llvm::Twine("Unexpected host CPU ").concat(ActualCpu));
+ }
const std::unique_ptr<BenchmarkRunner> Runner =
ExitOnErr(State.getExegesisTarget().createBenchmarkRunner(
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