[llvm-mca] Introduce the llvm-mca library and organize the directory accordingly. NFC.

Summary:
This patch introduces llvm-mca as a library.  The driver (llvm-mca.cpp), views, and stats, are not part of the library. 
Those are separate components that are not required for the functioning of llvm-mca.

The directory has been organized as follows:
All library source files now reside in:
  - `lib/HardwareUnits/` - All subclasses of HardwareUnit (these represent the simulated hardware components of a backend).
      (LSUnit does not inherit from HardwareUnit, but Scheduler does which uses LSUnit).  
  - `lib/Stages/` - All subclasses of the pipeline stages.
  - `lib/` - This is the root of the library and contains library code that does not fit into the Stages or HardwareUnit subdirs.

All library header files now reside in the `include` directory and mimic the same layout as the `lib` directory mentioned above.

In the (near) future we would like to move the library (include and lib) contents from tools and into the core of llvm somewhere.
That change would allow various analysis and optimization passes to make use of MCA  functionality for things like cost modeling.

I left all of the non-library code just where it has always been, in the root of the llvm-mca directory. 
The include directives for the non-library source file have been updated to refer to the llvm-mca library headers.
I updated the llvm-mca/CMakeLists.txt file to include the library headers, but I made the non-library code
explicitly reference the library's 'include' directory.  Once we eventually (hopefully) migrate the MCA library
components into llvm the include directives used by the non-library source files will be updated to point to the
proper location in llvm.

Reviewers: andreadb, courbet, RKSimon

Reviewed By: andreadb

Subscribers: mgorny, javed.absar, tschuett, gbedwell, llvm-commits

Differential Revision: https://reviews.llvm.org/D50929

llvm-svn: 340755

1 files changed, 79 insertions, 0 deletions

diff --git a/llvm/tools/llvm-mca/lib/Support.cpp b/llvm/tools/llvm-mca/lib/Support.cpp
new file mode 100644
index 00000000000..8f6b8a91f38
--- /dev/null
+++ b/llvm/tools/llvm-mca/lib/Support.cpp
@@ -0,0 +1,79 @@
+//===--------------------- Support.cpp --------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file implements a few helper functions used by various pipeline
+/// components.
+///
+//===----------------------------------------------------------------------===//
+
+#include "Support.h"
+#include "llvm/MC/MCSchedule.h"
+
+namespace mca {
+
+using namespace llvm;
+
+void computeProcResourceMasks(const MCSchedModel &SM,
+                              SmallVectorImpl<uint64_t> &Masks) {
+  unsigned ProcResourceID = 0;
+
+  // Create a unique bitmask for every processor resource unit.
+  // Skip resource at index 0, since it always references 'InvalidUnit'.
+  Masks.resize(SM.getNumProcResourceKinds());
+  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+    const MCProcResourceDesc &Desc = *SM.getProcResource(I);
+    if (Desc.SubUnitsIdxBegin)
+      continue;
+    Masks[I] = 1ULL << ProcResourceID;
+    ProcResourceID++;
+  }
+
+  // Create a unique bitmask for every processor resource group.
+  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+    const MCProcResourceDesc &Desc = *SM.getProcResource(I);
+    if (!Desc.SubUnitsIdxBegin)
+      continue;
+    Masks[I] = 1ULL << ProcResourceID;
+    for (unsigned U = 0; U < Desc.NumUnits; ++U) {
+      uint64_t OtherMask = Masks[Desc.SubUnitsIdxBegin[U]];
+      Masks[I] |= OtherMask;
+    }
+    ProcResourceID++;
+  }
+}
+
+double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth,
+                               unsigned NumMicroOps,
+                               ArrayRef<unsigned> ProcResourceUsage) {
+  // The block throughput is bounded from above by the hardware dispatch
+  // throughput. That is because the DispatchWidth is an upper bound on the
+  // number of opcodes that can be part of a single dispatch group.
+  double Max = static_cast<double>(NumMicroOps) / DispatchWidth;
+
+  // The block throughput is also limited by the amount of hardware parallelism.
+  // The number of available resource units affects the resource pressure
+  // distribution, as well as how many blocks can be executed every cycle.
+  for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+    unsigned ResourceCycles = ProcResourceUsage[I];
+    if (!ResourceCycles)
+      continue;
+
+    const MCProcResourceDesc &MCDesc = *SM.getProcResource(I);
+    double Throughput = static_cast<double>(ResourceCycles) / MCDesc.NumUnits;
+    Max = std::max(Max, Throughput);
+  }
+
+  // The block reciprocal throughput is computed as the MAX of:
+  //  - (NumMicroOps / DispatchWidth)
+  //  - (NumUnits / ResourceCycles)   for every consumed processor resource.
+  return Max;
+}
+
+} // namespace mca