[CIR][ABI][NFC] Make createLowerModule public (#734)

Although currently LowerModule is not ready for formal usage, we need it
for target-specific lowering to LLVM. This PR temporarily public the
symbol `createLowerModule` to reuse the logic of preparing a
`LowerModule`, making it easier for future refactor (making
`TargetLoweringInfo` available for most stages in CIR Lowering).

clang/lib/CIR/Dialect/Transforms/CallConvLowering.cpp

@@ -6,17 +6,13 @@
 //
 //===----------------------------------------------------------------------===//
 
-// FIXME(cir): This header file is not exposed to the public API, but can be
-// reused by CIR ABI lowering since it holds target-specific information.
-#include "../../../Basic/Targets.h"
 
 #include "TargetLowering/LowerModule.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
-#include "clang/Basic/TargetOptions.h"
 #include "clang/CIR/Dialect/IR/CIRDialect.h"
 
 #define GEN_PASS_DEF_CALLCONVLOWERING
@@ -25,35 +21,6 @@
 namespace mlir {
 namespace cir {
 
-namespace {
-
-LowerModule createLowerModule(FuncOp op, PatternRewriter &rewriter) {
-  auto module = op->getParentOfType<mlir::ModuleOp>();
-
-  // Fetch the LLVM data layout string.
-  auto dataLayoutStr = cast<StringAttr>(
-      module->getAttr(LLVM::LLVMDialect::getDataLayoutAttrName()));
-
-  // Fetch target information.
-  llvm::Triple triple(
-      cast<StringAttr>(module->getAttr("cir.triple")).getValue());
-  clang::TargetOptions targetOptions;
-  targetOptions.Triple = triple.str();
-  auto targetInfo = clang::targets::AllocateTarget(triple, targetOptions);
-
-  // FIXME(cir): This just uses the default language options. We need to account
-  // for custom options.
-  // Create context.
-  assert(!::cir::MissingFeatures::langOpts());
-  clang::LangOptions langOpts;
-  auto context = CIRLowerContext(module, langOpts);
-  context.initBuiltinTypes(*targetInfo);
-
-  return LowerModule(context, module, dataLayoutStr, *targetInfo, rewriter);
-}
-
-} // namespace
-
 //===----------------------------------------------------------------------===//
 // Rewrite Patterns
 //===----------------------------------------------------------------------===//
@@ -68,7 +35,8 @@ struct CallConvLoweringPattern : public OpRewritePattern<FuncOp> {
     if (!op.getAst())
       return op.emitError("function has no AST information");
 
-    LowerModule lowerModule = createLowerModule(op, rewriter);
+    auto modOp = op->getParentOfType<ModuleOp>();
+    LowerModule lowerModule = createLowerModule(modOp, rewriter);
 
     // Rewrite function calls before definitions. This should be done before
     // lowering the definition.

clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerModule.cpp

@@ -11,10 +11,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "LowerModule.h"
+// FIXME(cir): This header file is not exposed to the public API, but can be
+// reused by CIR ABI lowering since it holds target-specific information.
+#include "../../../../Basic/Targets.h"
+#include "clang/Basic/TargetOptions.h"
+
 #include "CIRLowerContext.h"
 #include "LowerFunction.h"
+#include "LowerModule.h"
 #include "TargetInfo.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/BuiltinAttributes.h"
 #include "mlir/IR/PatternMatch.h"
@@ -208,5 +214,29 @@ LogicalResult LowerModule::rewriteFunctionCall(CallOp callOp, FuncOp funcOp) {
   return success();
 }
 
+// TODO: not to create it every time
+LowerModule createLowerModule(ModuleOp module, PatternRewriter &rewriter) {
+  // Fetch the LLVM data layout string.
+  auto dataLayoutStr = cast<StringAttr>(
+      module->getAttr(LLVM::LLVMDialect::getDataLayoutAttrName()));
+
+  // Fetch target information.
+  llvm::Triple triple(
+      cast<StringAttr>(module->getAttr("cir.triple")).getValue());
+  clang::TargetOptions targetOptions;
+  targetOptions.Triple = triple.str();
+  auto targetInfo = clang::targets::AllocateTarget(triple, targetOptions);
+
+  // FIXME(cir): This just uses the default language options. We need to account
+  // for custom options.
+  // Create context.
+  assert(!::cir::MissingFeatures::langOpts());
+  clang::LangOptions langOpts;
+  auto context = CIRLowerContext(module, langOpts);
+  context.initBuiltinTypes(*targetInfo);
+
+  return LowerModule(context, module, dataLayoutStr, *targetInfo, rewriter);
+}
+
 } // namespace cir
 } // namespace mlir

clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerModule.h

@@ -91,6 +91,8 @@ class LowerModule {
   LogicalResult rewriteFunctionCall(CallOp callOp, FuncOp funcOp);
 };
 
+LowerModule createLowerModule(ModuleOp module, PatternRewriter &rewriter);
+
 } // namespace cir
 } // namespace mlir