From ad4586f401dead36742f7662bb018d35725c6dd3 Mon Sep 17 00:00:00 2001
From: Antonio Frighetto <antoniofrighetto@rev.ng>
Date: Wed, 24 Feb 2021 22:50:28 +0100
Subject: [PATCH] ProgramCounterHandler: add `dissectJumpablePC`

The new method `dissectJumpablePC` provides information about the
PC CSVs and allows not to make architecture-specific assumptions.
---
 include/revng/Support/ProgramCounterHandler.h |  5 ++
 lib/Support/ProgramCounterHandler.cpp         | 62 ++++++++++++++-----
 2 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/include/revng/Support/ProgramCounterHandler.h b/include/revng/Support/ProgramCounterHandler.h
index 03c4521e1..486728604 100644
--- a/include/revng/Support/ProgramCounterHandler.h
+++ b/include/revng/Support/ProgramCounterHandler.h
@@ -165,6 +165,11 @@ public:
 
   virtual llvm::Value *loadJumpablePC(llvm::IRBuilder<> &Builder) const = 0;
 
+  virtual std::array<llvm::Value *, 4>
+  dissectJumpablePC(llvm::IRBuilder<> &Builder,
+                    llvm::Value *ToDissect,
+                    llvm::Triple::ArchType Arch) const = 0;
+
   virtual void
   deserializePCFromSignalContext(llvm::IRBuilder<> &Builder,
                                  llvm::Value *PCAddress,
diff --git a/lib/Support/ProgramCounterHandler.cpp b/lib/Support/ProgramCounterHandler.cpp
index 838f7e1df..a76f583b6 100644
--- a/lib/Support/ProgramCounterHandler.cpp
+++ b/lib/Support/ProgramCounterHandler.cpp
@@ -51,6 +51,19 @@ public:
     return Builder.CreateLoad(AddressCSV);
   }
 
+  std::array<Value *, 4> dissectJumpablePC(IRBuilder<> &Builder,
+                                           Value *ToDissect,
+                                           Triple::ArchType Arch) const final {
+    IntegerType *Ty = getCSVType(TypeCSV);
+
+    Value *Address = ToDissect;
+    Value *Epoch = ConstantInt::get(Ty, 0);
+    Value *AddressSpace = ConstantInt::get(Ty, 0);
+    Value *Type = ConstantInt::get(Ty,
+                                   MetaAddressType::defaultCodeFromArch(Arch));
+    return { Address, Epoch, AddressSpace, Type };
+  }
+
   void deserializePCFromSignalContext(IRBuilder<> &Builder,
                                       Value *PCAddress,
                                       Value *SavedRegisters) const final {
@@ -109,24 +122,11 @@ private:
     revng_assert(affectsPC(Store));
 
     Value *Pointer = Store->getPointerOperand();
-    Value *StoredValue = Store->getValueOperand();
+    Value *ThumbValue = Store->getValueOperand();
 
     if (Pointer == IsThumb) {
-      // Update Type
-      using CI = ConstantInt;
-      using namespace MetaAddressType;
-
-      auto *TypeType = getCSVType(TypeCSV);
-      auto *ArmCode = CI::get(TypeType, Code_arm);
-      auto *ThumbCode = CI::get(TypeType, Code_arm_thumb);
-      // We don't use select here, SCEV can't handle it
-      // NewType = ARM + IsThumb * (Thumb - ARM)
-      auto *NewType = B.CreateAdd(ArmCode,
-                                  B.CreateMul(B.CreateTrunc(StoredValue,
-                                                            TypeType),
-                                              B.CreateSub(ThumbCode, ArmCode)));
-
-      B.CreateStore(NewType, TypeCSV);
+      // Compute Type and update it.
+      B.CreateStore(this->emitARMState(B, ThumbValue), TypeCSV);
 
       return true;
     }
@@ -142,6 +142,21 @@ private:
                                                AddressType));
   }
 
+  std::array<Value *, 4> dissectJumpablePC(IRBuilder<> &Builder,
+                                           Value *ToDissect,
+                                           Triple::ArchType Arch) const final {
+    constexpr uint32_t ThumbMask = 0x1;
+    constexpr uint32_t AddressMask = 0xFFFFFFFE;
+    IntegerType *Ty = getCSVType(TypeCSV);
+
+    Value *IsThumb = Builder.CreateAnd(ToDissect, ThumbMask);
+    Value *Address = Builder.CreateAnd(ToDissect, AddressMask);
+    Value *Epoch = ConstantInt::get(Ty, 0);
+    Value *AddressSpace = ConstantInt::get(Ty, 0);
+    Value *Type = this->emitARMState(Builder, IsThumb);
+    return { Address, Epoch, AddressSpace, Type };
+  }
+
   void deserializePCFromSignalContext(IRBuilder<> &B,
                                       Value *PCAddress,
                                       Value *SavedRegisters) const final {
@@ -170,6 +185,21 @@ private:
     B.CreateStore(PCAddress, AddressCSV);
   }
 
+  Value *emitARMState(IRBuilder<> &B, Value *IsThumb) const {
+    using CI = ConstantInt;
+    using namespace MetaAddressType;
+
+    auto *TypeType = getCSVType(TypeCSV);
+    auto *ArmCode = CI::get(TypeType, Code_arm);
+    auto *ThumbCode = CI::get(TypeType, Code_arm_thumb);
+    // We don't use select here, SCEV can't handle it
+    // NewType = ARM + IsThumb * (Thumb - ARM)
+    auto *NewType = B.CreateAdd(ArmCode,
+                                B.CreateMul(B.CreateTrunc(IsThumb, TypeType),
+                                            B.CreateSub(ThumbCode, ArmCode)));
+    return NewType;
+  }
+
 protected:
   void
   initializePCInternal(IRBuilder<> &Builder, MetaAddress NewPC) const final {