[XRay] Use FDR Records+Visitors for Trace Loading

Summary:
In this change, we overhaul the implementation for loading
`llvm::xray::Trace` objects from files by using the combination of
specific FDR Record types and visitors breaking up the logic to
reconstitute an execution trace from flight-data recorder mode traces.

This change allows us to handle out-of-temporal order blocks as written
in files, and more consistently recreate an execution trace spanning
multiple blocks and threads. To do this, we use the `WallclockRecord`
associated with each block to maintain temporal order of blocks, before
attempting to recreate an execution trace.

The new addition in this change is the `TraceExpander` type which can be
thought of as a decompression/decoding routine. This allows us to
maintain the state of an execution environment (thread+process) and
create `XRayRecord` instances that fit nicely into the `Trace`
container. We don't have a specific unit test for the TraceExpander
type, since the end-to-end tests for the `llvm-xray convert` tools
already cover precisely this codepath.

This change completes the refactoring started with D50441.

Depends on D51911.

Reviewers: mboerger, eizan

Subscribers: mgorny, hiraditya, mgrang, llvm-commits

Differential Revision: https://reviews.llvm.org/D51912

llvm-svn: 341906

1 files changed, 92 insertions, 0 deletions

diff --git a/llvm/lib/XRay/FDRTraceExpander.cpp b/llvm/lib/XRay/FDRTraceExpander.cpp
new file mode 100644
index 00000000000..8e15db52ce6
--- /dev/null
+++ b/llvm/lib/XRay/FDRTraceExpander.cpp
@@ -0,0 +1,92 @@
+//===- FDRTraceExpander.cpp -----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/XRay/FDRTraceExpander.h"
+
+namespace llvm {
+namespace xray {
+
+void TraceExpander::resetCurrentRecord() {
+  if (BuildingFunction)
+    C(CurrentRecord);
+  BuildingFunction = false;
+  CurrentRecord.CallArgs.clear();
+}
+
+Error TraceExpander::visit(BufferExtents &) {
+  resetCurrentRecord();
+  return Error::success();
+}
+
+Error TraceExpander::visit(WallclockRecord &) { return Error::success(); }
+
+Error TraceExpander::visit(NewCPUIDRecord &R) {
+  CPUId = R.cpuid();
+  BaseTSC = R.tsc();
+  return Error::success();
+}
+
+Error TraceExpander::visit(TSCWrapRecord &R) {
+  BaseTSC = R.tsc();
+  return Error::success();
+}
+
+Error TraceExpander::visit(CustomEventRecord &) {
+  // TODO: Support custom event records in the future.
+  resetCurrentRecord();
+  return Error::success();
+}
+
+Error TraceExpander::visit(CallArgRecord &R) {
+  CurrentRecord.CallArgs.push_back(R.arg());
+  CurrentRecord.Type = RecordTypes::ENTER_ARG;
+  return Error::success();
+}
+
+Error TraceExpander::visit(PIDRecord &R) {
+  PID = R.pid();
+  return Error::success();
+}
+
+Error TraceExpander::visit(NewBufferRecord &R) {
+  if (IgnoringRecords)
+    IgnoringRecords = false;
+  TID = R.tid();
+  if (LogVersion == 2)
+    PID = R.tid();
+  return Error::success();
+}
+
+Error TraceExpander::visit(EndBufferRecord &) {
+  IgnoringRecords = true;
+  resetCurrentRecord();
+  return Error::success();
+}
+
+Error TraceExpander::visit(FunctionRecord &R) {
+  resetCurrentRecord();
+  if (!IgnoringRecords) {
+    BaseTSC += R.delta();
+    CurrentRecord.Type = R.recordType();
+    CurrentRecord.FuncId = R.functionId();
+    CurrentRecord.TSC = BaseTSC;
+    CurrentRecord.PId = PID;
+    CurrentRecord.TId = TID;
+    CurrentRecord.CPU = CPUId;
+    BuildingFunction = true;
+  }
+  return Error::success();
+}
+
+Error TraceExpander::flush() {
+  resetCurrentRecord();
+  return Error::success();
+}
+
+} // namespace xray
+} // namespace llvm