[flang-commits] [flang] [flang] Lower hlfir.cmpchar into inline implementation in simplify-hlfir-intrinsics (PR #155461)

[Slava Zakharin via flang-commits]

================
@@ -2078,6 +2078,213 @@ class ArrayShiftConversion : public mlir::OpRewritePattern<Op> {
   }
 };
 
+class CmpCharOpConversion : public mlir::OpRewritePattern<hlfir::CmpCharOp> {
+public:
+  using mlir::OpRewritePattern<hlfir::CmpCharOp>::OpRewritePattern;
+
+  llvm::LogicalResult
+  matchAndRewrite(hlfir::CmpCharOp cmp,
+                  mlir::PatternRewriter &rewriter) const override {
+
+    fir::FirOpBuilder builder{rewriter, cmp.getOperation()};
+    const mlir::Location &loc = cmp->getLoc();
+
+    auto toVariable =
+        [&builder,
+         &loc](mlir::Value val) -> std::pair<mlir::Value, hlfir::AssociateOp> {
+      mlir::Value opnd;
+      hlfir::AssociateOp associate;
+      if (mlir::isa<hlfir::ExprType>(val.getType())) {
+        hlfir::Entity entity{val};
+        mlir::NamedAttribute byRefAttr = fir::getAdaptToByRefAttr(builder);
+        associate = hlfir::genAssociateExpr(loc, builder, entity,
+                                            entity.getType(), "", byRefAttr);
+        opnd = associate.getBase();
+      } else {
+        opnd = val;
+      }
+      return {opnd, associate};
+    };
+
+    auto [lhsOpnd, lhsAssociate] = toVariable(cmp.getLchr());
+    auto [rhsOpnd, rhsAssociate] = toVariable(cmp.getRchr());
+
+    hlfir::Entity lhs{lhsOpnd};
+    hlfir::Entity rhs{rhsOpnd};
+
+    auto charTy = mlir::cast<fir::CharacterType>(lhs.getFortranElementType());
+    unsigned kind = charTy.getFKind();
+
+    auto bits = builder.getKindMap().getCharacterBitsize(kind);
+    auto intTy = builder.getIntegerType(bits);
+
+    auto idxTy = builder.getIndexType();
+    auto charLen1Ty =
+        fir::CharacterType::getSingleton(builder.getContext(), kind);
+    mlir::Type designatorType =
+        fir::ReferenceType::get(charLen1Ty, fir::isa_volatile_type(charTy));
+    auto idxAttr = builder.getIntegerAttr(idxTy, 0);
+
+    auto genExtractAndConvertToInt =
+        [&idxAttr, &intTy, &designatorType](
+            mlir::Location loc, fir::FirOpBuilder &builder,
+            hlfir::Entity &charStr, mlir::Value index, mlir::Value length) {
+          auto singleChr = hlfir::DesignateOp::create(
+              builder, loc, designatorType, charStr, /*component=*/{},
+              /*compShape=*/mlir::Value{}, hlfir::DesignateOp::Subscripts{},
+              /*substring=*/mlir::ValueRange{index, index},
+              /*complexPart=*/std::nullopt,
+              /*shape=*/mlir::Value{}, /*typeParams=*/mlir::ValueRange{length},
+              fir::FortranVariableFlagsAttr{});
+          auto chrVal = fir::LoadOp::create(builder, loc, singleChr);
+          mlir::Value intVal = fir::ExtractValueOp::create(
+              builder, loc, intTy, chrVal, builder.getArrayAttr(idxAttr));
+          return intVal;
+        };
+
+    mlir::arith::CmpIPredicate predicate = cmp.getPredicate();
+    mlir::Value oneIdx = builder.createIntegerConstant(loc, idxTy, 1);
+
+    mlir::Value lhsLen = builder.createConvert(
+        loc, idxTy, hlfir::genCharLength(loc, builder, lhs));
+    mlir::Value rhsLen = builder.createConvert(
+        loc, idxTy, hlfir::genCharLength(loc, builder, rhs));
+
+    enum class GenCmp { LeftToRight, LeftToBlank, BlankToRight };
+
+    mlir::Value zeroInt = builder.createIntegerConstant(loc, intTy, 0);
+    mlir::Value oneInt = builder.createIntegerConstant(loc, intTy, 1);
+    mlir::Value negOneInt = builder.createIntegerConstant(loc, intTy, -1);
+    mlir::Value blankInt = builder.createIntegerConstant(loc, intTy, ' ');
+
+    auto step = GenCmp::LeftToRight;
+    auto genCmp =
+        [&](mlir::Location loc, fir::FirOpBuilder &builder,
+            mlir::ValueRange index,
+            mlir::ValueRange reduxrgs) -> llvm::SmallVector<mlir::Value, 1> {
----------------
vzakhari wrote:

nit: please try to avoid cryptic names :)
```suggestion
            mlir::ValueRange reductionArgs) -> llvm::SmallVector<mlir::Value, 1> {
```

https://github.com/llvm/llvm-project/pull/155461