[llvm] fd13d7c - Re-land "[llvm-exegesis] Save target state before running the benchmark.

[Clement Courbet via llvm-commits]

Author: Clement Courbet
Date: 2020-11-04T08:34:33+01:00
New Revision: fd13d7ce09af2bcad6976b8f5207874992bdd908

URL: https://github.com/llvm/llvm-project/commit/fd13d7ce09af2bcad6976b8f5207874992bdd908
DIFF: https://github.com/llvm/llvm-project/commit/fd13d7ce09af2bcad6976b8f5207874992bdd908.diff

LOG: Re-land "[llvm-exegesis] Save target state before running the benchmark.

Use `__builtin_ia32_fxsave64` under __GNUC__, (_fxsave64) does not exist in old versions of
gcc (pre-9.1).

This reverts commit e128f9cafca4e72b089fcd1381af5a1ec656d987.

Added: 
    llvm/test/tools/llvm-exegesis/X86/uops-FLDENVm.s

Modified: 
    llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp
    llvm/tools/llvm-exegesis/lib/Target.cpp
    llvm/tools/llvm-exegesis/lib/Target.h
    llvm/tools/llvm-exegesis/lib/X86/Target.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/tools/llvm-exegesis/X86/uops-FLDENVm.s b/llvm/test/tools/llvm-exegesis/X86/uops-FLDENVm.s
new file mode 100644
index 000000000000..be182d8fcf5b
--- /dev/null
+++ b/llvm/test/tools/llvm-exegesis/X86/uops-FLDENVm.s
@@ -0,0 +1,6 @@
+# RUN: llvm-exegesis -mode=uops -opcode-name=FLDENVm,FLDL2E -repetition-mode=duplicate | FileCheck %s
+
+CHECK:      mode:            uops
+CHECK-NEXT: key:
+CHECK-NEXT:   instructions:
+CHECK-NEXT:     FLDENVm

diff  --git a/llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp b/llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp
index 1bbad207a27e..2304e91b8b32 100644
--- a/llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp
+++ b/llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp
@@ -71,10 +71,10 @@ class FunctionExecutorImpl : public BenchmarkRunner::FunctionExecutor {
     SmallVector<StringRef, 2> CounterNames;
     StringRef(Counters).split(CounterNames, '+');
     char *const ScratchPtr = Scratch->ptr();
+    const ExegesisTarget &ET = State.getExegesisTarget();
     for (auto &CounterName : CounterNames) {
       CounterName = CounterName.trim();
-      auto CounterOrError =
-          State.getExegesisTarget().createCounter(CounterName, State);
+      auto CounterOrError = ET.createCounter(CounterName, State);
 
       if (!CounterOrError)
         return CounterOrError.takeError();
@@ -93,6 +93,7 @@ class FunctionExecutorImpl : public BenchmarkRunner::FunctionExecutor {
                 .concat(std::to_string(Reserved)));
       Scratch->clear();
       {
+        auto PS = ET.withSavedState();
         CrashRecoveryContext CRC;
         CrashRecoveryContext::Enable();
         const bool Crashed = !CRC.RunSafely([this, Counter, ScratchPtr]() {
@@ -101,6 +102,7 @@ class FunctionExecutorImpl : public BenchmarkRunner::FunctionExecutor {
           Counter->stop();
         });
         CrashRecoveryContext::Disable();
+        PS.reset();
         if (Crashed) {
           std::string Msg = "snippet crashed while running";
 #ifdef LLVM_ON_UNIX

diff  --git a/llvm/tools/llvm-exegesis/lib/Target.cpp b/llvm/tools/llvm-exegesis/lib/Target.cpp
index ad26c1678c78..85180a1d6614 100644
--- a/llvm/tools/llvm-exegesis/lib/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/Target.cpp
@@ -147,6 +147,8 @@ const PfmCountersInfo &ExegesisTarget::getPfmCounters(StringRef CpuName) const {
   return *Found->PCI;
 }
 
+ExegesisTarget::SavedState::~SavedState() {} // anchor.
+
 namespace {
 
 // Default implementation.

diff  --git a/llvm/tools/llvm-exegesis/lib/Target.h b/llvm/tools/llvm-exegesis/lib/Target.h
index 8a5624b42803..28c103aa1948 100644
--- a/llvm/tools/llvm-exegesis/lib/Target.h
+++ b/llvm/tools/llvm-exegesis/lib/Target.h
@@ -172,6 +172,16 @@ class ExegesisTarget {
   // counters are defined for this CPU).
   const PfmCountersInfo &getPfmCounters(StringRef CpuName) const;
 
+  // Saves the CPU state that needs to be preserved when running a benchmark,
+  // and returns and RAII object that restores the state on destruction.
+  // By default no state is preserved.
+  struct SavedState {
+    virtual ~SavedState();
+  };
+  virtual std::unique_ptr<SavedState> withSavedState() const {
+    return std::make_unique<SavedState>();
+  }
+
 private:
   virtual bool matchesArch(Triple::ArchType Arch) const = 0;
 

diff  --git a/llvm/tools/llvm-exegesis/lib/X86/Target.cpp b/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
index 827e2e27a2f8..8610afdeb9e5 100644
--- a/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
+++ b/llvm/tools/llvm-exegesis/lib/X86/Target.cpp
@@ -26,6 +26,9 @@
 #include <memory>
 #include <string>
 #include <vector>
+#if defined(_MSC_VER)
+#include <immintrin.h>
+#endif
 
 namespace llvm {
 namespace exegesis {
@@ -594,6 +597,32 @@ void ConstantInliner::initStack(unsigned Bytes) {
 
 namespace {
 
+class X86SavedState : public ExegesisTarget::SavedState {
+public:
+  X86SavedState() {
+#if defined(_MSC_VER)
+    _fxsave64(FPState);
+#elif defined(__GNUC__)
+    __builtin_ia32_fxsave64(FPState);
+#endif
+  }
+
+  ~X86SavedState() {
+    // Restoring the X87 state does not flush pending exceptions, make sure
+    // these exceptions are flushed now.
+#if defined(_MSC_VER)
+    _clearfp();
+    _fxrstor64(FPState);
+#elif defined(__GNUC__)
+    asm volatile("fwait");
+    __builtin_ia32_fxrstor64(FPState);
+#endif
+  }
+
+private:
+  alignas(16) char FPState[512];
+};
+
 class ExegesisX86Target : public ExegesisTarget {
 public:
   ExegesisX86Target() : ExegesisTarget(X86CpuPfmCounters) {}
@@ -691,6 +720,10 @@ class ExegesisX86Target : public ExegesisTarget {
 #endif
   }
 
+  std::unique_ptr<SavedState> withSavedState() const override {
+    return std::make_unique<X86SavedState>();
+  }
+
   static const unsigned kUnavailableRegisters[4];
 };