Add llvm-exegesis tool.

Summary:
[llvm-exegesis][RFC] Automatic Measurement of Instruction Latency/Uops

This is the code corresponding to the RFC "llvm-exegesis Automatic Measurement of Instruction Latency/Uops".

The RFC is available on the LLVM mailing lists as well as the following document
for easier reading:
https://docs.google.com/document/d/1QidaJMJUyQdRrFKD66vE1_N55whe0coQ3h1GpFzz27M/edit?usp=sharing

Subscribers: mgorny, gchatelet, orwant, llvm-commits

Differential Revision: https://reviews.llvm.org/D44519

llvm-svn: 329156

1 files changed, 56 insertions, 0 deletions

diff --git a/llvm/tools/llvm-exegesis/lib/LlvmState.cpp b/llvm/tools/llvm-exegesis/lib/LlvmState.cpp
new file mode 100644
index 00000000000..cb534f50998
--- /dev/null
+++ b/llvm/tools/llvm-exegesis/lib/LlvmState.cpp
@@ -0,0 +1,56 @@
+//===-- LlvmState.cpp -------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LlvmState.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+
+namespace exegesis {
+
+LLVMState::LLVMState()
+    : TheTriple(llvm::sys::getProcessTriple()),
+      CpuName(llvm::sys::getHostCPUName().str()) {
+  std::string Error;
+  TheTarget = llvm::TargetRegistry::lookupTarget(TheTriple, Error);
+  assert(TheTarget && "unknown target for host");
+  SubtargetInfo.reset(
+      TheTarget->createMCSubtargetInfo(TheTriple, CpuName, Features));
+  InstrInfo.reset(TheTarget->createMCInstrInfo());
+  RegInfo.reset(TheTarget->createMCRegInfo(TheTriple));
+  AsmInfo.reset(TheTarget->createMCAsmInfo(*RegInfo, TheTriple));
+}
+
+std::unique_ptr<llvm::LLVMTargetMachine>
+LLVMState::createTargetMachine() const {
+  const llvm::TargetOptions Options;
+  return std::unique_ptr<llvm::LLVMTargetMachine>(
+      static_cast<llvm::LLVMTargetMachine *>(TheTarget->createTargetMachine(
+          TheTriple, CpuName, Features, Options, llvm::Reloc::Model::Static)));
+}
+
+bool LLVMState::canAssemble(const llvm::MCInst &Inst) const {
+  llvm::MCObjectFileInfo ObjectFileInfo;
+  llvm::MCContext Context(AsmInfo.get(), RegInfo.get(), &ObjectFileInfo);
+  std::unique_ptr<const llvm::MCCodeEmitter> CodeEmitter(
+      TheTarget->createMCCodeEmitter(*InstrInfo, *RegInfo, Context));
+  llvm::SmallVector<char, 16> Tmp;
+  llvm::raw_svector_ostream OS(Tmp);
+  llvm::SmallVector<llvm::MCFixup, 4> Fixups;
+  CodeEmitter->encodeInstruction(Inst, OS, Fixups, *SubtargetInfo);
+  return Tmp.size() > 0;
+}
+
+} // namespace exegesis