Implement variableTypeChanges() for basic cases

Author: adazem009

src/engine/internal/llvm/CMakeLists.txt

@@ -17,6 +17,8 @@ target_sources(scratchcpp
     llvmtypes.h
     llvmfunctions.cpp
     llvmloopscope.h
+    llvmloopanalyzer.cpp
+    llvmloopanalyzer.h
     llvmcompilercontext.cpp
     llvmcompilercontext.h
     llvmexecutablecode.cpp

src/engine/internal/llvm/llvmloopanalyzer.cpp

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#include "llvmloopanalyzer.h"
+#include "llvminstruction.h"
+#include "llvmvariableptr.h"
+
+using namespace libscratchcpp;
+
+bool LLVMLoopAnalyzer::variableTypeChanges(LLVMVariablePtr *varPtr, LLVMInstruction *loopBody, Compiler::StaticType preLoopType) const
+{
+    if (!varPtr || !loopBody)
+        return false;
+
+    if (preLoopType == Compiler::StaticType::Unknown)
+        return true;
+
+    // Find the last write instruction
+    LLVMInstruction *lastVarWrite = nullptr;
+    LLVMInstruction *ins = loopBody;
+
+    while (ins && ins->type != LLVMInstruction::Type::EndLoop) {
+        // TODO: Handle nested loops
+        if (ins->type == LLVMInstruction::Type::WriteVariable && ins->workVariable == varPtr->var)
+            lastVarWrite = ins;
+
+        ins = ins->next;
+    }
+
+    // Loops must always have an end instruction
+    assert(ins);
+
+    // Check the last write instruction, if any
+    return lastVarWrite ? !typesMatch(lastVarWrite, preLoopType) : false;
+}
+
+Compiler::StaticType LLVMLoopAnalyzer::optimizeRegisterType(LLVMRegister *reg) const
+{
+    // TODO: Move this method out if it's used in LLVMCodeBuilder too
+    assert(reg);
+
+    Compiler::StaticType ret = reg->type();
+
+    // Optimize string constants that represent numbers
+    if (reg->isConst() && reg->type() == Compiler::StaticType::String && reg->constValue().isValidNumber())
+        ret = Compiler::StaticType::Number;
+
+    return ret;
+}
+
+bool LLVMLoopAnalyzer::typesMatch(LLVMInstruction *ins, Compiler::StaticType expectedType) const
+{
+    assert(ins);
+    assert(!ins->args.empty());
+    const auto arg = ins->args.back().second; // value is always the last argument in variable/list write instructions
+    auto argIns = arg->instruction;
+
+    // TODO: Handle cross-variable dependencies
+    /*if (argIns && (argIns->type == LLVMInstruction::Type::ReadVariable || argIns->type == LLVMInstruction::Type::GetListItem))
+        return isVarOrListTypeSafe(argIns.get(), expectedType, log, c);*/
+
+    return (optimizeRegisterType(arg) == expectedType);
+}

src/engine/internal/llvm/llvmloopanalyzer.h

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#include <scratchcpp/compiler.h>
+
+namespace libscratchcpp
+{
+
+struct LLVMVariablePtr;
+struct LLVMInstruction;
+struct LLVMRegister;
+
+class LLVMLoopAnalyzer
+{
+    public:
+        bool variableTypeChanges(LLVMVariablePtr *varPtr, LLVMInstruction *loopBody, Compiler::StaticType preLoopType) const;
+
+    private:
+        Compiler::StaticType optimizeRegisterType(LLVMRegister *reg) const;
+        bool typesMatch(LLVMInstruction *ins, Compiler::StaticType expectedType) const;
+};
+
+} // namespace libscratchcpp

test/llvm/CMakeLists.txt

@@ -20,6 +20,7 @@ add_executable(
   llvmexecutablecode_test.cpp
   llvmcodebuilder_test.cpp
   llvminstructionlist_test.cpp
+  loop_analyzer/variabletypechanges_test.cpp
 )
 
 target_link_libraries(