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, 38 insertions, 0 deletions

diff --git a/llvm/tools/llvm-exegesis/lib/X86.cpp b/llvm/tools/llvm-exegesis/lib/X86.cpp
new file mode 100644
index 00000000000..c9afece4a9f
--- /dev/null
+++ b/llvm/tools/llvm-exegesis/lib/X86.cpp
@@ -0,0 +1,38 @@
+//===-- X86.cpp --------------------------------------------------*- C++-*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "X86.h"
+
+namespace exegesis {
+
+static llvm::Error makeError(llvm::Twine Msg) {
+  return llvm::make_error<llvm::StringError>(Msg,
+                                             llvm::inconvertibleErrorCode());
+}
+
+X86Filter::~X86Filter() = default;
+
+// Test whether we can generate a snippet for this instruction.
+llvm::Error X86Filter::shouldRun(const LLVMState &State,
+                                 const unsigned Opcode) const {
+  const auto &InstrInfo = State.getInstrInfo();
+  const llvm::MCInstrDesc &InstrDesc = InstrInfo.get(Opcode);
+  if (InstrDesc.isBranch() || InstrDesc.isIndirectBranch())
+    return makeError("Unsupported opcode: isBranch/isIndirectBranch");
+  if (InstrDesc.isCall() || InstrDesc.isReturn())
+    return makeError("Unsupported opcode: isCall/isReturn");
+  const auto OpcodeName = InstrInfo.getName(Opcode);
+  if (OpcodeName.startswith("POPF") || OpcodeName.startswith("PUSHF") ||
+      OpcodeName.startswith("ADJCALLSTACK")) {
+    return makeError("Unsupported opcode: Push/Pop/AdjCallStack");
+  }
+  return llvm::ErrorSuccess();
+}
+
+} // namespace exegesis