CIRPasses.cpp

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements machinery for any CIR <-> CIR passes used by clang.
//
//===----------------------------------------------------------------------===//
 
#include "mlir/IR/BuiltinOps.h"
#include "mlir/Pass/PassManager.h"
#include "clang/Basic/LangOptions.h"
#include "clang/CIR/Dialect/IR/CIRDialect.h"
#include "clang/CIR/Dialect/Passes.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/TargetParser/Triple.h"
 
namespace cir {
 
/// Map a target triple to the ABI target that drives CallConvLowering.
/// Returns None for targets whose calling convention is not yet implemented.
static CallConvTarget getCallConvTarget(const llvm::Triple &triple) {
  // Windows is not supported.  UEFI shares its convention.
  if (triple.getArch() == llvm::Triple::x86_64 && !triple.isOSWindowsOrUEFI())
    return CallConvTarget::X86_64;
  return CallConvTarget::None;
}
 
/// The AVX level the classifier uses to size a native vector, read from the
/// target ABI name.
static llvm::abi::X86AVXABILevel getX86AVXABILevel(llvm::StringRef abi) {
  if (abi == "avx512")
    return llvm::abi::X86AVXABILevel::AVX512;
  if (abi == "avx")
    return llvm::abi::X86AVXABILevel::AVX;
  return llvm::abi::X86AVXABILevel::None;
}
 
/// Whether `__attribute__((target(...)))` on a function may raise its AVX ABI
/// level above the command line's.  A target that opts out, and any ABI older
/// than the rule, stay at the module level.
static bool allowsX86TargetAttrAvx(const llvm::Triple &triple,
                                   clang::LangOptions::ClangABI compat) {
  return !triple.isPS() && compat > clang::LangOptions::ClangABI::Ver23;
}
 
/// The x86_64 ABI-compatibility flags, derived from the target and the
/// requested compatibility version.  Every flag defaults to true in the ABI
/// library, which is not what any target computes: Clang11Compat is false for a
/// modern Linux target, so leaving it at the default classifies a union larger
/// than an eightbyte as though every member spanned its size.
static llvm::abi::X86ABICompatInfo
getX86ABICompatInfo(const llvm::Triple &triple,
                    clang::LangOptions::ClangABI compat) {
  llvm::abi::X86ABICompatInfo abiCompat;
  abiCompat.HonorsRevision98 = !triple.isOSDarwin();
  abiCompat.ClassifyIntegerMMXAsSSE =
      compat > clang::LangOptions::ClangABI::Ver3_8 && !triple.isOSDarwin() &&
      !triple.isPS() && !triple.isOSFreeBSD();
  abiCompat.PassInt128VectorsInMem =
      compat > clang::LangOptions::ClangABI::Ver9 &&
      (triple.isOSLinux() || triple.isOSNetBSD());
  abiCompat.ReturnCXXRecordGreaterThan128InMem =
      compat > clang::LangOptions::ClangABI::Ver20 && !triple.isPS();
  abiCompat.Clang11Compat =
      compat <= clang::LangOptions::ClangABI::Ver11 || triple.isPS();
  return abiCompat;
}
 
mlir::LogicalResult
runCIRToCIRPasses(mlir::ModuleOp theModule, mlir::MLIRContext &mlirContext,
                  bool enableVerifier, bool enableIdiomRecognizer,
                  bool enableCIRSimplify, bool enableLibOpt,
                  llvm::StringRef libOptOptions, bool enableCallConvLowering) {
 
  llvm::TimeTraceScope scope("CIR To CIR Passes");
 
  std::optional<llvm::Triple> triple = cir::getTripleFromModule(theModule);
  if (!triple)
    return theModule.emitError()
           << "missing '" << cir::CIRDialect::getTripleAttrName()
           << "' attribute";
 
  auto abiAttr = theModule->getAttrOfType<mlir::StringAttr>(
      cir::CIRDialect::getTargetABIAttrName());
  if (!abiAttr)
    return theModule.emitError()
           << "missing '" << cir::CIRDialect::getTargetABIAttrName()
           << "' attribute";
 
  mlir::PassManager pm(&mlirContext);
  pm.addPass(mlir::createCIRCanonicalizePass());
 
  if (enableCIRSimplify)
    pm.addPass(mlir::createCIRSimplifyPass());
 
  if (enableIdiomRecognizer)
    pm.addPass(mlir::createIdiomRecognizerPass());
 
  if (enableLibOpt) {
    auto libOptPass = mlir::createLibOptPass();
    auto errorHandler = [](const llvm::Twine &) -> mlir::LogicalResult {
      return mlir::LogicalResult::failure();
    };
 
    if (libOptPass->initializeOptions(libOptOptions, errorHandler).failed())
      return mlir::failure();
 
    pm.addPass(std::move(libOptPass));
  }
 
  pm.addPass(mlir::createTargetLoweringPass());
  pm.addPass(mlir::createCXXABILoweringPass());
 
  // LoweringPrepare synthesizes calls to runtime helpers such as __divsc3, and
  // outlines dynamic global initializers into functions.  It must run before
  // CallConvLowering so the classifier sees them, otherwise their signatures
  // go unclassified and caller and callee disagree on the ABI.
  pm.addPass(mlir::createLoweringPreparePass());
 
  if (enableCallConvLowering) {
    // CallConvLowering rewrites signatures and call sites using the classifier,
    // so it must run after CXXABILowering has lowered C++ ABI types to plain
    // records the classifier can handle.  Only the x86_64 System V classifier
    // is implemented; other targets are left unchanged.
    CallConvTarget target = getCallConvTarget(*triple);
    if (target != CallConvTarget::None) {
      // Source the ABI-compatibility version from the module's serialized
      // #cir.lowering_options so a reloaded .cir classifies the same way
      // it was compiled, without a live clang::LangOptions. CIRGen sets this
      // attribute at module construction; if it is absent fall back to the
      // LangOptions default, matching how LowerModule reads the same attribute.
      auto compat = clang::LangOptions::ClangABI::Latest;
      if (auto loweringLangOpts =
              theModule->getAttrOfType<cir::LoweringOptionsAttr>(
                  cir::CIRDialect::getLoweringOptionsAttrName()))
        compat = static_cast<clang::LangOptions::ClangABI>(
            loweringLangOpts.getClangAbiCompat());
      pm.addPass(mlir::createCallConvLoweringPass(
          target, getX86AVXABILevel(abiAttr.getValue()),
          allowsX86TargetAttrAvx(*triple, compat),
          getX86ABICompatInfo(*triple, compat)));
    }
  }
 
  pm.enableVerifier(enableVerifier);
  (void)mlir::applyPassManagerCLOptions(pm);
  return pm.run(theModule);
}
 
} // namespace cir
 
namespace mlir {
 
void populateCIRPreLoweringPasses(OpPassManager &pm) {
  pm.addPass(createHoistAllocasPass());
  pm.addPass(createCIRFlattenCFGPass());
  pm.addPass(createCIREHABILoweringPass());
  pm.addPass(createGotoSolverPass());
  pm.addPass(createCIRFoldEmptyBranchesPass());
}
 
} // namespace mlir