flang/lib/Optimizer/Transforms/CharacterConversion.cpp

   1 //===- CharacterConversion.cpp -- convert between character encodings -----===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "flang/Optimizer/Dialect/FIRDialect.h"
  10 #include "flang/Optimizer/Dialect/FIROps.h"
  11 #include "flang/Optimizer/Dialect/FIRType.h"
  12 #include "flang/Optimizer/Dialect/Support/FIRContext.h"
  13 #include "flang/Optimizer/Dialect/Support/KindMapping.h"
  14 #include "flang/Optimizer/Transforms/Passes.h"
  15 #include "mlir/Dialect/Affine/IR/AffineOps.h"
  16 #include "mlir/Dialect/Func/IR/FuncOps.h"
  17 #include "mlir/IR/Diagnostics.h"
  18 #include "mlir/Pass/Pass.h"
  19 #include "mlir/Transforms/DialectConversion.h"
  20 #include "llvm/Support/Debug.h"
  21
  22 namespace fir {
  23 #define GEN_PASS_DEF_CHARACTERCONVERSION
  24 #include "flang/Optimizer/Transforms/Passes.h.inc"
  25 } // namespace fir
  26
  27 #define DEBUG_TYPE "flang-character-conversion"
  28
  29 namespace {
  30
  31 // TODO: Future hook to select some set of runtime calls.
  32 struct CharacterConversionOptions {
  33   std::string runtimeName;
  34 };
  35
  36 class CharacterConvertConversion
  37     : public mlir::OpRewritePattern<fir::CharConvertOp> {
  38 public:
  39   using OpRewritePattern::OpRewritePattern;
  40
  41   llvm::LogicalResult
  42   matchAndRewrite(fir::CharConvertOp conv,
  43                   mlir::PatternRewriter &rewriter) const override {
  44     auto kindMap = fir::getKindMapping(conv->getParentOfType<mlir::ModuleOp>());
  45     auto loc = conv.getLoc();
  46
  47     LLVM_DEBUG(llvm::dbgs()
  48                << "running character conversion on " << conv << '\n');
  49
  50     // Establish a loop that executes count iterations.
  51     auto zero = rewriter.create<mlir::arith::ConstantIndexOp>(loc, 0);
  52     auto one = rewriter.create<mlir::arith::ConstantIndexOp>(loc, 1);
  53     auto idxTy = rewriter.getIndexType();
  54     auto castCnt = rewriter.create<fir::ConvertOp>(loc, idxTy, conv.getCount());
  55     auto countm1 = rewriter.create<mlir::arith::SubIOp>(loc, castCnt, one);
  56     auto loop = rewriter.create<fir::DoLoopOp>(loc, zero, countm1, one);
  57     auto insPt = rewriter.saveInsertionPoint();
  58     rewriter.setInsertionPointToStart(loop.getBody());
  59
  60     // For each code point in the `from` string, convert naively to the `to`
  61     // string code point. Conversion is done blindly on size only, not value.
  62     auto getCharBits = [&](mlir::Type t) {
  63       auto chrTy = mlir::cast<fir::CharacterType>(
  64           fir::unwrapSequenceType(fir::dyn_cast_ptrEleTy(t)));
  65       return kindMap.getCharacterBitsize(chrTy.getFKind());
  66     };
  67     auto fromBits = getCharBits(conv.getFrom().getType());
  68     auto toBits = getCharBits(conv.getTo().getType());
  69     auto pointerType = [&](unsigned bits) {
  70       return fir::ReferenceType::get(fir::SequenceType::get(
  71           fir::SequenceType::ShapeRef{fir::SequenceType::getUnknownExtent()},
  72           rewriter.getIntegerType(bits)));
  73     };
  74     auto fromPtrTy = pointerType(fromBits);
  75     auto toTy = rewriter.getIntegerType(toBits);
  76     auto toPtrTy = pointerType(toBits);
  77     auto fromPtr =
  78         rewriter.create<fir::ConvertOp>(loc, fromPtrTy, conv.getFrom());
  79     auto toPtr = rewriter.create<fir::ConvertOp>(loc, toPtrTy, conv.getTo());
  80     auto getEleTy = [&](unsigned bits) {
  81       return fir::ReferenceType::get(rewriter.getIntegerType(bits));
  82     };
  83     auto fromi = rewriter.create<fir::CoordinateOp>(
  84         loc, getEleTy(fromBits), fromPtr,
  85         mlir::ValueRange{loop.getInductionVar()});
  86     auto toi = rewriter.create<fir::CoordinateOp>(
  87         loc, getEleTy(toBits), toPtr, mlir::ValueRange{loop.getInductionVar()});
  88     auto load = rewriter.create<fir::LoadOp>(loc, fromi);
  89     mlir::Value icast =
  90         (fromBits >= toBits)
  91             ? rewriter.create<fir::ConvertOp>(loc, toTy, load).getResult()
  92             : rewriter.create<mlir::arith::ExtUIOp>(loc, toTy, load)
  93                   .getResult();
  94     rewriter.replaceOpWithNewOp<fir::StoreOp>(conv, icast, toi);
  95     rewriter.restoreInsertionPoint(insPt);
  96     return mlir::success();
  97   }
  98 };
  99
 100 /// Rewrite the `fir.char_convert` op into a loop. This pass must be run only on
 101 /// fir::CharConvertOp.
 102 class CharacterConversion
 103     : public fir::impl::CharacterConversionBase<CharacterConversion> {
 104 public:
 105   using fir::impl::CharacterConversionBase<
 106       CharacterConversion>::CharacterConversionBase;
 107
 108   void runOnOperation() override {
 109     CharacterConversionOptions clOpts{useRuntimeCalls.getValue()};
 110     if (clOpts.runtimeName.empty()) {
 111       auto *context = &getContext();
 112       auto *func = getOperation();
 113       mlir::RewritePatternSet patterns(context);
 114       patterns.insert<CharacterConvertConversion>(context);
 115       mlir::ConversionTarget target(*context);
 116       target.addLegalDialect<mlir::affine::AffineDialect, fir::FIROpsDialect,
 117                              mlir::arith::ArithDialect,
 118                              mlir::func::FuncDialect>();
 119
 120       // apply the patterns
 121       target.addIllegalOp<fir::CharConvertOp>();
 122       if (mlir::failed(mlir::applyPartialConversion(func, target,
 123                                                     std::move(patterns)))) {
 124         mlir::emitError(mlir::UnknownLoc::get(context),
 125                         "error in rewriting character convert op");
 126         signalPassFailure();
 127       }
 128       return;
 129     }
 130
 131     // TODO: some sort of runtime supported conversion?
 132     signalPassFailure();
 133   }
 134 };
 135 } // end anonymous namespace