Revert "[CIR] Lowering to LLVM for global pointers (llvm#125619)"

This reverts commit 2b5cc89.

Author: lanza

clang/include/clang/CIR/Dialect/IR/CIRAttrVisitor.h

@@ -27,9 +27,6 @@ struct MissingFeatures {
   // Address space related
   static bool addressSpace() { return false; }
 
-  // This isn't needed until we add support for bools.
-  static bool convertTypeForMemory() { return false; }
-
   // Unhandled global/linkage information.
   static bool opGlobalDSOLocal() { return false; }
   static bool opGlobalThreadLocal() { return false; }

clang/include/clang/CIR/MissingFeatures.h

@@ -24,7 +24,6 @@
 #include "mlir/Target/LLVMIR/Dialect/LLVMIR/LLVMToLLVMIRTranslation.h"
 #include "mlir/Target/LLVMIR/Export.h"
 #include "mlir/Transforms/DialectConversion.h"
-#include "clang/CIR/Dialect/IR/CIRAttrVisitor.h"
 #include "clang/CIR/Dialect/IR/CIRDialect.h"
 #include "clang/CIR/MissingFeatures.h"
 #include "llvm/IR/Module.h"
@@ -36,71 +35,6 @@ using namespace llvm;
 namespace cir {
 namespace direct {
 
-class CIRAttrToValue : public CirAttrVisitor<CIRAttrToValue, mlir::Value> {
-public:
-  CIRAttrToValue(mlir::Operation *parentOp,
-                 mlir::ConversionPatternRewriter &rewriter,
-                 const mlir::TypeConverter *converter)
-      : parentOp(parentOp), rewriter(rewriter), converter(converter) {}
-
-  mlir::Value lowerCirAttrAsValue(mlir::Attribute attr) { return visit(attr); }
-
-  mlir::Value visitCirIntAttr(cir::IntAttr intAttr) {
-    mlir::Location loc = parentOp->getLoc();
-    return rewriter.create<mlir::LLVM::ConstantOp>(
-        loc, converter->convertType(intAttr.getType()), intAttr.getValue());
-  }
-
-  mlir::Value visitCirFPAttr(cir::FPAttr fltAttr) {
-    mlir::Location loc = parentOp->getLoc();
-    return rewriter.create<mlir::LLVM::ConstantOp>(
-        loc, converter->convertType(fltAttr.getType()), fltAttr.getValue());
-  }
-
-  mlir::Value visitCirConstPtrAttr(cir::ConstPtrAttr ptrAttr) {
-    mlir::Location loc = parentOp->getLoc();
-    if (ptrAttr.isNullValue()) {
-      return rewriter.create<mlir::LLVM::ZeroOp>(
-          loc, converter->convertType(ptrAttr.getType()));
-    }
-    mlir::DataLayout layout(parentOp->getParentOfType<mlir::ModuleOp>());
-    mlir::Value ptrVal = rewriter.create<mlir::LLVM::ConstantOp>(
-        loc,
-        rewriter.getIntegerType(layout.getTypeSizeInBits(ptrAttr.getType())),
-        ptrAttr.getValue().getInt());
-    return rewriter.create<mlir::LLVM::IntToPtrOp>(
-        loc, converter->convertType(ptrAttr.getType()), ptrVal);
-  }
-
-private:
-  mlir::Operation *parentOp;
-  mlir::ConversionPatternRewriter &rewriter;
-  const mlir::TypeConverter *converter;
-};
-
-// This class handles rewriting initializer attributes for types that do not
-// require region initialization.
-class GlobalInitAttrRewriter
-    : public CirAttrVisitor<GlobalInitAttrRewriter, mlir::Attribute> {
-public:
-  GlobalInitAttrRewriter(mlir::Type type,
-                         mlir::ConversionPatternRewriter &rewriter)
-      : llvmType(type), rewriter(rewriter) {}
-
-  mlir::Attribute rewriteInitAttr(mlir::Attribute attr) { return visit(attr); }
-
-  mlir::Attribute visitCirIntAttr(cir::IntAttr attr) {
-    return rewriter.getIntegerAttr(llvmType, attr.getValue());
-  }
-  mlir::Attribute visitCirFPAttr(cir::FPAttr attr) {
-    return rewriter.getFloatAttr(llvmType, attr.getValue());
-  }
-
-private:
-  mlir::Type llvmType;
-  mlir::ConversionPatternRewriter &rewriter;
-};
-
 // This pass requires the CIR to be in a "flat" state. All blocks in each
 // function must belong to the parent region. Once scopes and control flow
 // are implemented in CIR, a pass will be run before this one to flatten
@@ -121,81 +55,14 @@ struct ConvertCIRToLLVMPass
   StringRef getArgument() const override { return "cir-flat-to-llvm"; }
 };
 
-bool CIRToLLVMGlobalOpLowering::attrRequiresRegionInitialization(
-    mlir::Attribute attr) const {
-  // There will be more cases added later.
-  return isa<cir::ConstPtrAttr>(attr);
-}
-
-/// Replace CIR global with a region initialized LLVM global and update
-/// insertion point to the end of the initializer block.
-void CIRToLLVMGlobalOpLowering::setupRegionInitializedLLVMGlobalOp(
-    cir::GlobalOp op, mlir::ConversionPatternRewriter &rewriter) const {
-  assert(!cir::MissingFeatures::convertTypeForMemory());
-  const mlir::Type llvmType = getTypeConverter()->convertType(op.getSymType());
-
-  // FIXME: These default values are placeholders until the the equivalent
-  //        attributes are available on cir.global ops. This duplicates code
-  //        in CIRToLLVMGlobalOpLowering::matchAndRewrite() but that will go
-  //        away when the placeholders are no longer needed.
-  assert(!cir::MissingFeatures::opGlobalConstant());
-  const bool isConst = false;
-  assert(!cir::MissingFeatures::addressSpace());
-  const unsigned addrSpace = 0;
-  assert(!cir::MissingFeatures::opGlobalDSOLocal());
-  const bool isDsoLocal = true;
-  assert(!cir::MissingFeatures::opGlobalThreadLocal());
-  const bool isThreadLocal = false;
-  assert(!cir::MissingFeatures::opGlobalAlignment());
-  const uint64_t alignment = 0;
-  assert(!cir::MissingFeatures::opGlobalLinkage());
-  const mlir::LLVM::Linkage linkage = mlir::LLVM::Linkage::External;
-  const StringRef symbol = op.getSymName();
-
-  SmallVector<mlir::NamedAttribute> attributes;
-  auto newGlobalOp = rewriter.replaceOpWithNewOp<mlir::LLVM::GlobalOp>(
-      op, llvmType, isConst, linkage, symbol, nullptr, alignment, addrSpace,
-      isDsoLocal, isThreadLocal,
-      /*comdat=*/mlir::SymbolRefAttr(), attributes);
-  newGlobalOp.getRegion().push_back(new mlir::Block());
-  rewriter.setInsertionPointToEnd(newGlobalOp.getInitializerBlock());
-};
-
-mlir::LogicalResult
-CIRToLLVMGlobalOpLowering::matchAndRewriteRegionInitializedGlobal(
-    cir::GlobalOp op, mlir::Attribute init,
-    mlir::ConversionPatternRewriter &rewriter) const {
-  // TODO: Generalize this handling when more types are needed here.
-  assert(isa<cir::ConstPtrAttr>(init));
-
-  // TODO(cir): once LLVM's dialect has proper equivalent attributes this
-  // should be updated. For now, we use a custom op to initialize globals
-  // to the appropriate value.
-  const mlir::Location loc = op.getLoc();
-  setupRegionInitializedLLVMGlobalOp(op, rewriter);
-  CIRAttrToValue attrVisitor(op, rewriter, typeConverter);
-  mlir::Value value = attrVisitor.lowerCirAttrAsValue(init);
-  rewriter.create<mlir::LLVM::ReturnOp>(loc, value);
-  return mlir::success();
-}
-
 mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
     cir::GlobalOp op, OpAdaptor adaptor,
     mlir::ConversionPatternRewriter &rewriter) const {
 
-  std::optional<mlir::Attribute> init = op.getInitialValue();
-
-  // If we have an initializer and it requires region initialization, handle
-  // that separately
-  if (init.has_value() && attrRequiresRegionInitialization(init.value())) {
-    return matchAndRewriteRegionInitializedGlobal(op, init.value(), rewriter);
-  }
-
   // Fetch required values to create LLVM op.
   const mlir::Type cirSymType = op.getSymType();
 
   // This is the LLVM dialect type.
-  assert(!cir::MissingFeatures::convertTypeForMemory());
   const mlir::Type llvmType = getTypeConverter()->convertType(cirSymType);
   // FIXME: These default values are placeholders until the the equivalent
   //        attributes are available on cir.global ops.
@@ -212,15 +79,20 @@ mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
   assert(!cir::MissingFeatures::opGlobalLinkage());
   const mlir::LLVM::Linkage linkage = mlir::LLVM::Linkage::External;
   const StringRef symbol = op.getSymName();
+  std::optional<mlir::Attribute> init = op.getInitialValue();
+
   SmallVector<mlir::NamedAttribute> attributes;
 
   if (init.has_value()) {
-    GlobalInitAttrRewriter initRewriter(llvmType, rewriter);
-    init = initRewriter.rewriteInitAttr(init.value());
-    // If initRewriter returned a null attribute, init will have a value but
-    // the value will be null. If that happens, initRewriter didn't handle the
-    // attribute type. It probably needs to be added to GlobalInitAttrRewriter.
-    if (!init.value()) {
+    if (const auto fltAttr = mlir::dyn_cast<cir::FPAttr>(init.value())) {
+      // Initializer is a constant floating-point number: convert to MLIR
+      // builtin constant.
+      init = rewriter.getFloatAttr(llvmType, fltAttr.getValue());
+    } else if (const auto intAttr =
+                   mlir::dyn_cast<cir::IntAttr>(init.value())) {
+      // Initializer is a constant array: convert it to a compatible llvm init.
+      init = rewriter.getIntegerAttr(llvmType, intAttr.getValue());
+    } else {
       op.emitError() << "unsupported initializer '" << init.value() << "'";
       return mlir::failure();
     }
@@ -237,13 +109,6 @@ mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
 
 static void prepareTypeConverter(mlir::LLVMTypeConverter &converter,
                                  mlir::DataLayout &dataLayout) {
-  converter.addConversion([&](cir::PointerType type) -> mlir::Type {
-    // Drop pointee type since LLVM dialect only allows opaque pointers.
-    assert(!cir::MissingFeatures::addressSpace());
-    unsigned targetAS = 0;
-
-    return mlir::LLVM::LLVMPointerType::get(type.getContext(), targetAS);
-  });
   converter.addConversion([&](cir::IntType type) -> mlir::Type {
     // LLVM doesn't work with signed types, so we drop the CIR signs here.
     return mlir::IntegerType::get(type.getContext(), type.getWidth());

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -34,16 +34,6 @@ class CIRToLLVMGlobalOpLowering
   mlir::LogicalResult
   matchAndRewrite(cir::GlobalOp op, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override;
-
-private:
-  bool attrRequiresRegionInitialization(mlir::Attribute attr) const;
-
-  mlir::LogicalResult matchAndRewriteRegionInitializedGlobal(
-      cir::GlobalOp op, mlir::Attribute init,
-      mlir::ConversionPatternRewriter &rewriter) const;
-
-  void setupRegionInitializedLLVMGlobalOp(
-      cir::GlobalOp op, mlir::ConversionPatternRewriter &rewriter) const;
 };
 
 } // namespace direct

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h

@@ -79,24 +79,3 @@ long double ld;
 
 __float128 f128;
 // CHECK: @f128 = external dso_local global fp128
-
-void *vp;
-// CHECK: @vp = external dso_local global ptr{{$}}
-
-int *ip = 0;
-// CHECK: @ip = dso_local global ptr null
-
-double *dp;
-// CHECK: @dp = external dso_local global ptr{{$}}
-
-char **cpp;
-// CHECK: @cpp = external dso_local global ptr{{$}}
-
-void (*fp)();
-// CHECK: @fp = external dso_local global ptr{{$}}
-
-int (*fpii)(int) = 0;
-// CHECK: @fpii = dso_local global ptr null
-
-void (*fpvar)(int, ...);
-// CHECK: @fpvar = external dso_local global ptr{{$}}