From ac0c6d3071088fbf713d77f0b904484692ea19f9 Mon Sep 17 00:00:00 2001
From: Quentin Colombet <qcolombet@apple.com>
Date: Fri, 26 Aug 2016 22:32:53 +0000
Subject: [PATCH] [MachineFunction] Introduce a reset method.

This method allows to reset the state of a MachineFunction as if it was
just created. This will be used during the bring-up of GlobalISel to
provide a way to fallback on SelectionDAG. That way, we can start doing
correctness testing even if we are not able to select all functions via
the global instruction selector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279876 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/MachineFunction.h | 17 +++++++++++++++++
 lib/CodeGen/MachineFunction.cpp        | 19 ++++++++++++++-----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/include/llvm/CodeGen/MachineFunction.h b/include/llvm/CodeGen/MachineFunction.h
index ad72e84c07d..57b7bc6bf70 100644
--- a/include/llvm/CodeGen/MachineFunction.h
+++ b/include/llvm/CodeGen/MachineFunction.h
@@ -238,11 +238,28 @@ class MachineFunction {
 
   MachineFunction(const MachineFunction &) = delete;
   void operator=(const MachineFunction&) = delete;
+
+  /// Clear all the members of this MachineFunction, but the ones used
+  /// to initialize again the MachineFunction.
+  /// More specifically, this deallocates all the dynamically allocated
+  /// objects and get rid of all the XXXInfo data structure, but keep
+  /// unchanged the references to Fn, Target, MMI, and FunctionNumber.
+  void clear();
+  /// Allocate and initialize the different members.
+  /// In particular, the XXXInfo data structure.
+  /// \pre Fn, Target, MMI, and FunctionNumber are properly set.
+  void init();
 public:
   MachineFunction(const Function *Fn, const TargetMachine &TM,
                   unsigned FunctionNum, MachineModuleInfo &MMI);
   ~MachineFunction();
 
+  /// Reset the instance as if it was just created.
+  void reset() {
+    clear();
+    init();
+  }
+
   MachineModuleInfo &getMMI() const { return MMI; }
   MCContext &getContext() const { return Ctx; }
 
diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index f5c8147d859..08c93f20946 100644
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -100,6 +100,11 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
                                  unsigned FunctionNum, MachineModuleInfo &mmi)
     : Fn(F), Target(TM), STI(TM.getSubtargetImpl(*F)), Ctx(mmi.getContext()),
       MMI(mmi) {
+  FunctionNumber = FunctionNum;
+  init();
+}
+
+void MachineFunction::init() {
   // Assume the function starts in SSA form with correct liveness.
   Properties.set(MachineFunctionProperties::Property::IsSSA);
   Properties.set(MachineFunctionProperties::Property::TracksLiveness);
@@ -112,11 +117,11 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
   // We can realign the stack if the target supports it and the user hasn't
   // explicitly asked us not to.
   bool CanRealignSP = STI->getFrameLowering()->isStackRealignable() &&
-                      !F->hasFnAttribute("no-realign-stack");
+                      !Fn->hasFnAttribute("no-realign-stack");
   FrameInfo = new (Allocator) MachineFrameInfo(
       getFnStackAlignment(STI, Fn), /*StackRealignable=*/CanRealignSP,
       /*ForceRealign=*/CanRealignSP &&
-          F->hasFnAttribute(Attribute::StackAlignment));
+          Fn->hasFnAttribute(Attribute::StackAlignment));
 
   if (Fn->hasFnAttribute(Attribute::StackAlignment))
     FrameInfo->ensureMaxAlignment(Fn->getFnStackAlignment());
@@ -133,15 +138,14 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
   if (AlignAllFunctions)
     Alignment = AlignAllFunctions;
 
-  FunctionNumber = FunctionNum;
   JumpTableInfo = nullptr;
 
   if (isFuncletEHPersonality(classifyEHPersonality(
-          F->hasPersonalityFn() ? F->getPersonalityFn() : nullptr))) {
+          Fn->hasPersonalityFn() ? Fn->getPersonalityFn() : nullptr))) {
     WinEHInfo = new (Allocator) WinEHFuncInfo();
   }
 
-  assert(TM.isCompatibleDataLayout(getDataLayout()) &&
+  assert(Target.isCompatibleDataLayout(getDataLayout()) &&
          "Can't create a MachineFunction using a Module with a "
          "Target-incompatible DataLayout attached\n");
 
@@ -149,6 +153,11 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
 }
 
 MachineFunction::~MachineFunction() {
+  clear();
+}
+
+void MachineFunction::clear() {
+  Properties.reset();
   // Don't call destructors on MachineInstr and MachineOperand. All of their
   // memory comes from the BumpPtrAllocator which is about to be purged.
   //
-- 
2.11.0