[mlir][emitc] Add EmitC lowering for arith.trunci, arith.extsi, arith.extui

This commit adds conversion to EmitC for arith dialect casts between integer types (trunc, extsi, extui), excluding indexes for now.

mlir/lib/Conversion/ArithToEmitC/ArithToEmitC.cpp

@@ -15,6 +15,7 @@
 
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Tools/PDLL/AST/Types.h"
 #include "mlir/Transforms/DialectConversion.h"
 
 using namespace mlir;
@@ -112,6 +113,93 @@ public:
   }
 };
 
+template <typename ArithOp, bool castToUnsigned>
+class CastConversion : public OpConversionPattern<ArithOp> {
+public:
+  using OpConversionPattern<ArithOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(ArithOp op, typename ArithOp::Adaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+
+    Type opReturnType = this->getTypeConverter()->convertType(op.getType());
+    if (!isa_and_nonnull<IntegerType>(opReturnType))
+      return rewriter.notifyMatchFailure(op, "expected integer result type");
+
+    if (adaptor.getOperands().size() != 1) {
+      return rewriter.notifyMatchFailure(
+          op, "CastConversion only supports unary ops");
+    }
+
+    Type operandType = adaptor.getIn().getType();
+    if (!isa_and_nonnull<IntegerType>(operandType))
+      return rewriter.notifyMatchFailure(op, "expected integer operand type");
+
+    // Signed (sign-extending) casts from i1 are not supported.
+    if (operandType.isInteger(1) && !castToUnsigned)
+      return rewriter.notifyMatchFailure(op,
+                                         "operation not supported on i1 type");
+
+    // to-i1 conversions: arith semantics want truncation, whereas (bool)(v) is
+    // equivalent to (v != 0). Implementing as (bool)(v & 0x01) gives
+    // truncation.
+    if (opReturnType.isInteger(1)) {
+      auto constOne = rewriter.create<emitc::ConstantOp>(
+          op.getLoc(), operandType, rewriter.getIntegerAttr(operandType, 1));
+      auto oneAndOperand = rewriter.create<emitc::BitwiseAndOp>(
+          op.getLoc(), operandType, adaptor.getIn(), constOne);
+      rewriter.replaceOpWithNewOp<emitc::CastOp>(op, opReturnType,
+                                                 oneAndOperand);
+      return success();
+    }
+
+    bool isTruncation = operandType.getIntOrFloatBitWidth() >
+                        opReturnType.getIntOrFloatBitWidth();
+    bool doUnsigned = castToUnsigned || isTruncation;
+
+    Type castType = opReturnType;
+    // If the op is a ui variant and the type wanted as
+    // return type isn't unsigned, we need to issue an unsigned type to do
+    // the conversion.
+    if (castType.isUnsignedInteger() != doUnsigned) {
+      castType = rewriter.getIntegerType(opReturnType.getIntOrFloatBitWidth(),
+                                         /*isSigned=*/!doUnsigned);
+    }
+
+    Value actualOp = adaptor.getIn();
+    // Adapt the signedness of the operand if necessary
+    if (operandType.isUnsignedInteger() != doUnsigned) {
+      Type correctSignednessType =
+          rewriter.getIntegerType(operandType.getIntOrFloatBitWidth(),
+                                  /*isSigned=*/!doUnsigned);
+      actualOp = rewriter.template create<emitc::CastOp>(
+          op.getLoc(), correctSignednessType, actualOp);
+    }
+
+    auto result = rewriter.template create<emitc::CastOp>(op.getLoc(), castType,
+                                                          actualOp);
+
+    // Cast to the expected output type
+    if (castType != opReturnType) {
+      result = rewriter.template create<emitc::CastOp>(op.getLoc(),
+                                                       opReturnType, result);
+    }
+
+    rewriter.replaceOp(op, result);
+    return success();
+  }
+};
+
+template <typename ArithOp>
+class UnsignedCastConversion : public CastConversion<ArithOp, true> {
+  using CastConversion<ArithOp, true>::CastConversion;
+};
+
+template <typename ArithOp>
+class SignedCastConversion : public CastConversion<ArithOp, false> {
+  using CastConversion<ArithOp, false>::CastConversion;
+};
+
 template <typename ArithOp, typename EmitCOp>
 class ArithOpConversion final : public OpConversionPattern<ArithOp> {
 public:
@@ -313,6 +401,10 @@ void mlir::populateArithToEmitCPatterns(TypeConverter &typeConverter,
     IntegerOpConversion<arith::SubIOp, emitc::SubOp>,
     CmpIOpConversion,
     SelectOpConversion,
+    // Truncation is guaranteed for unsigned types.
+    UnsignedCastConversion<arith::TruncIOp>,
+    SignedCastConversion<arith::ExtSIOp>,
+    UnsignedCastConversion<arith::ExtUIOp>,
     ItoFCastOpConversion<arith::SIToFPOp>,
     ItoFCastOpConversion<arith::UIToFPOp>,
     FtoICastOpConversion<arith::FPToSIOp>,

mlir/test/Conversion/ArithToEmitC/arith-to-emitc-unsupported.mlir

@@ -63,3 +63,10 @@ func.func @arith_cast_fptoui_i1(%arg0: f32) -> i1 {
   return %t: i1
 }
 
+// -----
+
+func.func @arith_extsi_i1_to_i32(%arg0: i1) {
+  // expected-error @+1 {{failed to legalize operation 'arith.extsi'}}
+  %idx = arith.extsi %arg0 : i1 to i32
+  return
+}

mlir/test/Conversion/ArithToEmitC/arith-to-emitc.mlir

@@ -177,3 +177,66 @@ func.func @arith_int_to_float_cast_ops(%arg0: i8, %arg1: i64) {
 
   return
 }
+
+// -----
+
+func.func @arith_trunci(%arg0: i32) -> i8 {
+  // CHECK-LABEL: arith_trunci
+  // CHECK-SAME: (%[[Arg0:[^ ]*]]: i32)
+  // CHECK: %[[CastUI:.*]] = emitc.cast %[[Arg0]] : i32 to ui32
+  // CHECK: %[[Trunc:.*]] = emitc.cast %[[CastUI]] : ui32 to ui8
+  // CHECK: emitc.cast %[[Trunc]] : ui8 to i8
+  %truncd = arith.trunci %arg0 : i32 to i8
+
+  return %truncd : i8
+}
+
+// -----
+
+func.func @arith_trunci_to_i1(%arg0: i32) -> i1 {
+  // CHECK-LABEL: arith_trunci_to_i1
+  // CHECK-SAME: (%[[Arg0:[^ ]*]]: i32)
+  // CHECK: %[[Const:.*]] = "emitc.constant"
+  // CHECK-SAME: value = 1
+  // CHECK: %[[And:.*]] = emitc.bitwise_and %[[Arg0]], %[[Const]] : (i32, i32) -> i32
+  // CHECK: emitc.cast %[[And]] : i32 to i1
+  %truncd = arith.trunci %arg0 : i32 to i1
+
+  return %truncd : i1
+}
+
+// -----
+
+func.func @arith_extsi(%arg0: i32) {
+  // CHECK-LABEL: arith_extsi
+  // CHECK-SAME: ([[Arg0:[^ ]*]]: i32)
+  // CHECK: emitc.cast [[Arg0]] : i32 to i64
+  %extd = arith.extsi %arg0 : i32 to i64
+
+  return
+}
+
+// -----
+
+func.func @arith_extui(%arg0: i32) {
+  // CHECK-LABEL: arith_extui
+  // CHECK-SAME: (%[[Arg0:[^ ]*]]: i32)
+  // CHECK: %[[Conv0:.*]] = emitc.cast %[[Arg0]] : i32 to ui32
+  // CHECK: %[[Conv1:.*]] = emitc.cast %[[Conv0]] : ui32 to ui64
+  // CHECK: emitc.cast %[[Conv1]] : ui64 to i64
+  %extd = arith.extui %arg0 : i32 to i64
+
+  return
+}
+
+// -----
+
+func.func @arith_extui_i1_to_i32(%arg0: i1) {
+  // CHECK-LABEL: arith_extui_i1_to_i32
+  // CHECK-SAME: (%[[Arg0:[^ ]*]]: i1)
+  // CHECK: %[[Conv0:.*]] = emitc.cast %[[Arg0]] : i1 to ui1
+  // CHECK: %[[Conv1:.*]] = emitc.cast %[[Conv0]] : ui1 to ui32
+  // CHECK: emitc.cast %[[Conv1]] : ui32 to i32
+  %idx = arith.extui %arg0 : i1 to i32
+  return
+}