Add readme and some regalloc updates

Dependencies

• [2] SWF5OAWK Add Sanitized build config
• [3] MFTKDEMK Implement base algorithm
• [4] 7OVOGA6Q Import LLVM @ 15.0.7
• [*] WHVW6V3W

Change contents

• replacement in llvm/lib/CodeGen/RegAllocSimple.cpp at line 103
  [3.3420]→[3.3420:3421](∅→∅)
  −
  [3.3420]

  [3.3421]
  + assert(MO.getReg().isVirtual() && "Can only allocate a virtual register");

  +
• replacement in llvm/lib/CodeGen/RegAllocSimple.cpp at line 160
  [3.5319]→[3.5319:5500](∅→∅)
  − auto const allocUse = [this](MachineOperand &MO){ this->allocateOperand(MO, true); };

  − auto const allocDef = [this](MachineOperand &MO){ this->allocateOperand(MO, false); };
  [3.5319]

  [3.5500]
  + auto const allocUse = [this](MachineOperand &MO){

  + assert(MO.isUse());

  + LLVM_DEBUG(dbgs() << "Regalloc: Allocating use " << MO << "\n");

  + this->allocateOperand(MO, true);

  + };

  + auto const allocDef = [this](MachineOperand &MO){

  + assert(MO.isDef());

  + LLVM_DEBUG(dbgs() << "Regalloc: Allocating def " << MO << "\n");

  + this->allocateOperand(MO, false);

  + };
• edit in llvm/lib/CodeGen/RegAllocSimple.cpp at line 178
  [3.5712]

  [3.5712]
  + LLVM_DEBUG(dbgs() << "Regalloc: Spilling clobbered reg " << R << "\n");
• edit in llvm/lib/CodeGen/RegAllocSimple.cpp at line 238
  [3.7127]

  [3.7127]
  + assert(MO.getReg().isVirtual() && "Cannot bind a physical register to a non-virtual register");

  +
• replacement in llvm/CMakeLists.txt at line 87
  [4.642607700]→[4.642607700:642607967](∅→∅)
  − set(LLVM_ALL_PROJECTS "bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libc;libclc;libcxx;libcxxabi;libunwind;lld;lldb;mlir;openmp;polly;pstl")

  − # The flang project is not yet part of "all" projects (see C++ requirements)

  − set(LLVM_EXTRA_PROJECTS "flang")
  [4.642607700]

  [4.642607967]
  + ##

  + ## Removed projects not vendored

  + ##

  + set(LLVM_ALL_PROJECTS "clang")
• file addition: README.md (----------)
  [6.1]
  + This is a monorepo of my compiler projects that use LLVM. It is primarily intended to be built with Bazel, but CMake is also supported.

  +

  + `coollang/` contains the frontend and runtime for COOL (Classroom Object-Oriented Language), which is a small language that still supports static typing, garbage collection, polymorphism, and dynamic dispatch.

  +

  + `clang/` is the unmodified clang 15.0.7 source tree

  +

  + `llvm/` is the unmodified llvm 15.0.7 source tree with the addition of optimizations I developed:

  + - `llvm/lib/CodeGen/RegAllocSimple.cpp` is a bottom-up local register allocator

  + - `llvm/lib/Analysis/UnitLoopInfo.cpp` is a natural-loop detector

  + - `llvm/lib/Transforms/Scalar/UnitLICM.cpp` is a loop-invariant code motion pass

  + - `llvm/lib/Transforms/Scalar/UnitSCCP.cpp` is a sparse conditional-constant propagation pass

  +

  + Corresponding headers and tests can be found in the usual places
• replacement in .bazelrc at line 112
  [2.85014]→[2.85014:85034](∅→∅)
  − build --fission=yes
  [2.85014]

  [4.874196115]
  + #build --fission=yes