[ImportVerilog] Add conditional operator. (llvm#6950)

include/circt/Dialect/Moore/MooreOps.td

@@ -223,17 +223,18 @@ def NetOp : MooreOp<"net", [
 ]> {
   let summary = "A net declaration";
   let description = [{
-    The `moore.net' operation is a net declaration. Net types defines different types
-    of net connection in SV. There are twelve built-in net types defined in the official
-    standard construct of the operation:
-    `supply0`, `supply1`, `tri`, `triand`, `trior`, `trireg`, `tri0`, `tri1`, `uwire`,
-    `wire`, `wand`, `wor`.
-    Optional assignment argument allows net operation to be initialized with specific
-    values as soon as it is created. Only one net declaration assignment can be made for
-    a particular net. See IEEE 1800-2017 § 10.3.1 "The net declaration assignment" for
-    the differences between net declaration assignments and continuous assign statements.
-    It has some features that are not supported: declaring an interconnect net and using
-    user-defined types in the net operation.
+    The `moore.net' operation is a net declaration. Net types defines different
+    types of net connection in SV. There are twelve built-in net types defined
+    in the official standard construct of the operation:
+    `supply0`, `supply1`, `tri`, `triand`, `trior`, `trireg`, `tri0`, `tri1`,
+    `uwire`, `wire`, `wand`, `wor`.
+    Optional assignment argument allows net operation to be initialized with
+    specific values as soon as it is created. Only one net declaration
+    assignment can be made for a particular net. See IEEE 1800-2017 § 10.3.1
+    "The net declaration assignment" for the differences between net declaration
+    assignments and continuous assign statements. It has some features that are
+    not supported: declaring an interconnect net and using user-defined types in
+    the net operation.
 
     See IEEE 1800-2017 § 6.7 "Net declarations".
   }];
@@ -961,64 +962,130 @@ def StructInjectOp : MooreOp<"struct_inject"> {
 def UnionCreateOp : MooreOp<"union_create"> {
   let summary = "Union Create operation";
   let description = [{
-  A union is a data type that represents a single piece
-  of storage that can be accessed using one of
-  the named member data types. Only one of the
-  data types in the union can be used at a time.
-  By default, a union is unpacked, meaning there
-  is no required representation for how members
-  of the union are stored. Dynamic types and chandle
-  types can only be used in tagged unions.
-  See IEEE 1800-2017 § 7.3 "Unions"
-
-  Example:
-  ```
-  typedef union { int i; shortreal f; } num; // named union type
-  num n;
-  n.f = 0.0; // set n in floating point format
-  typedef struct {
-  bit isfloat;
-  union { int i; shortreal f; } n;           // anonymous union type
-  } tagged_st;                               // named structure
-  ```
-  See IEEE 1800-2017 § 7.3 "Unions"
+    A union is a data type that represents a single piece
+    of storage that can be accessed using one of
+    the named member data types. Only one of the
+    data types in the union can be used at a time.
+    By default, a union is unpacked, meaning there
+    is no required representation for how members
+    of the union are stored. Dynamic types and chandle
+    types can only be used in tagged unions.
+    See IEEE 1800-2017 § 7.3 "Unions"
+
+    Example:
+    ```
+    typedef union { int i; shortreal f; } num; // named union type
+    num n;
+    n.f = 0.0; // set n in floating point format
+    typedef struct {
+    bit isfloat;
+    union { int i; shortreal f; } n;           // anonymous union type
+    } tagged_st;                               // named structure
+    ```
+    See IEEE 1800-2017 § 7.3 "Unions"
   }];
   let arguments = (ins StrAttr:$unionName, UnpackedType:$input);
   let results = (outs UnpackedType:$result);
   let assemblyFormat = [{
   $unionName `,` $input attr-dict `:`
   type($input) `->` type($result)
   }];
- }
+}
 
- def UnionExtractOp : MooreOp<"union_extract"> {
+def UnionExtractOp : MooreOp<"union_extract"> {
   let summary = "Union Extract operation";
   let description = [{
-  With packed unions, writing one member and reading another is
-  independent of the byte ordering of the machine,
-  unlike an unpacked union of unpacked structures,
-  which are C-compatible and have members in ascending address order.
-  See IEEE 1800-2017 § 7.3.1 "Packed unions"
-
-  Example:
-  ```
-  typedef union packed { // default unsigned
-  s_atmcell acell;
-  bit [423:0] bit_slice;
-  bit [52:0][7:0] byte_slice;
-  } u_atmcell;
-  u_atmcell u1;
-  byte b; bit [3:0] nib;
-  b = u1.bit_slice[415:408]; // same as b = u1.byte_slice[51];
-  nib = u1.bit_slice [423:420];
-  ```
-  See IEEE 1800-2017 § 7.3.1 "Packed unions"
+    With packed unions, writing one member and reading another is
+    independent of the byte ordering of the machine,
+    unlike an unpacked union of unpacked structures,
+    which are C-compatible and have members in ascending address order.
+    See IEEE 1800-2017 § 7.3.1 "Packed unions"
+
+    Example:
+    ```
+    typedef union packed { // default unsigned
+    s_atmcell acell;
+    bit [423:0] bit_slice;
+    bit [52:0][7:0] byte_slice;
+    } u_atmcell;
+    u_atmcell u1;
+    byte b; bit [3:0] nib;
+    b = u1.bit_slice[415:408]; // same as b = u1.byte_slice[51];
+    nib = u1.bit_slice [423:420];
+    ```
+    See IEEE 1800-2017 § 7.3.1 "Packed unions"
   }];
   let arguments = (ins StrAttr:$memberName, UnpackedType:$input);
   let results = (outs UnpackedType:$result);
   let assemblyFormat = [{
   $input `,`   $memberName  attr-dict `:`
   type($input) `->` type($result)
   }];
- }
+}
+
+def ConditionalOp : MooreOp<"conditional",[
+  RecursiveMemoryEffects,
+  NoRegionArguments, 
+  SingleBlockImplicitTerminator<"moore::YieldOp">
+]> {
+  let summary = "Conditional operation";
+  let description = [{
+    If cond_predicate is true, the operator returns the value of the first 
+    expression without evaluating the second expression; if false, it returns 
+    the value of the second expression without evaluating the first expression.
+    If cond_predicate evaluates to an ambiguous value (x or z), then both the
+    first expression and the second expression shall be evaluated, and compared
+    for logical equivalence. If that comparison is true (1), the operator shall
+    return either the first or second expression. Otherwise the operator returns
+    a result based on the data types of the expressions.
+
+    When both the first and second expressions are of integral types, if the
+    cond_predicate evaluates to an ambiguous value and the expressions are not
+    logically equivalent, their results shall be combined bit by bit using the
+    table below to calculate the final result. The first and second expressions
+    are extended to the same width.
+
+    |?: | 0 | 1 | X | Z |
+    |---|---|---|---|---|
+    | 0 | 0 | X | X | X |
+    | 1 | X | 1 | X | X |
+    | X | X | X | X | X |
+    | Z | X | X | X | X |
+
+    See IEEE 1800-2017 § 11.4.11 "Conditional operator".
+  }];
+  let arguments = (ins AnySingleBitType:$condition);
+  let results = (outs UnpackedType:$result);
+  let regions = (region SizedRegion<1>:$trueRegion,
+                        SizedRegion<1>:$falseRegion);
+  let assemblyFormat = [{
+    $condition attr-dict `:` type($condition) `->` type($result)
+    $trueRegion $falseRegion
+  }];
+}
+
+def YieldOp : MooreOp<"yield", [
+  Pure, 
+  Terminator, 
+  HasParent<"ConditionalOp">
+]> {
+  let summary = "conditional yield and termination operation";
+  let description = [{
+    "moore.yield" yields an SSA value from the Moore dialect op region and
+    terminates the regions. The semantics of how the values are yielded is
+    defined by the parent operation.
+    If "moore.yield" has any operands, the operands must match the parent
+    operation's results.
+    If the parent operation defines no values, then the "moore.yield" may be
+    left out in the custom syntax and the builders will insert one implicitly.
+    Otherwise, it has to be present in the syntax to indicate which values are
+    yielded.
+  }];
+  let arguments = (ins UnpackedType:$result);
+  let builders = [OpBuilder<(ins), [{ /* nothing to do */ }]>];
+  let assemblyFormat = [{
+    attr-dict $result `:` type($result)
+  }];
+  let hasVerifier = 1;
+}
 #endif // CIRCT_DIALECT_MOORE_MOOREOPS

lib/Conversion/ImportVerilog/Expressions.cpp

@@ -514,6 +514,41 @@ struct ExprVisitor {
     return result;
   }
 
+  // Handle conditional operator `?:`.
+  Value visit(const slang::ast::ConditionalExpression &expr) {
+    auto type = context.convertType(*expr.type);
+
+    // Handle condition.
+    Value cond = convertToSimpleBitVector(
+        context.convertExpression(*expr.conditions.begin()->expr));
+    cond = convertToBool(cond);
+    if (!cond)
+      return {};
+    auto conditionalOp = builder.create<moore::ConditionalOp>(loc, type, cond);
+
+    // Create blocks for true region and false region.
+    conditionalOp.getTrueRegion().emplaceBlock();
+    conditionalOp.getFalseRegion().emplaceBlock();
+
+    OpBuilder::InsertionGuard g(builder);
+
+    // Handle left expression.
+    builder.setInsertionPointToStart(conditionalOp.getBody(0));
+    auto trueValue = context.convertExpression(expr.left());
+    if (!trueValue)
+      return {};
+    builder.create<moore::YieldOp>(loc, trueValue);
+
+    // Handle right expression.
+    builder.setInsertionPointToStart(conditionalOp.getBody(1));
+    auto falseValue = context.convertExpression(expr.right());
+    if (!falseValue)
+      return {};
+    builder.create<moore::YieldOp>(loc, falseValue);
+
+    return conditionalOp.getResult();
+  }
+
   /// Emit an error for all other expressions.
   template <typename T>
   Value visit(T &&node) {

lib/Dialect/Moore/MooreOps.cpp

@@ -353,6 +353,30 @@ LogicalResult ConcatOp::inferReturnTypes(
   return success();
 }
 
+//===----------------------------------------------------------------------===//
+// YieldOp
+//===----------------------------------------------------------------------===//
+
+LogicalResult YieldOp::verify() {
+  // Check that YieldOp's parent operation is ConditionalOp.
+  auto cond = dyn_cast<ConditionalOp>(*(*this).getParentOp());
+  if (!cond) {
+    emitOpError("must have a conditional parent");
+    return failure();
+  }
+
+  // Check that the operand matches the parent operation's result.
+  auto condType = cond.getType();
+  auto yieldType = getOperand().getType();
+  if (condType != yieldType) {
+    emitOpError("yield type must match conditional. Expected ")
+        << condType << ", but got " << yieldType << ".";
+    return failure();
+  }
+
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // ConversionOp
 //===----------------------------------------------------------------------===//

test/Conversion/ImportVerilog/basic.sv

@@ -350,6 +350,9 @@ module Expressions;
       int a, b;
     } c, d;
   } union1;
+  // CHECK: %r1 = moore.variable : real
+  // CHECK: %r2 = moore.variable : real
+  real r1,r2;
 
   initial begin
     // CHECK: moore.constant 0 : i32
@@ -600,6 +603,41 @@ module Expressions;
     // CHECK: moore.or [[TMP1]], [[TMP6]] : i1
     c = a inside { a, b, [a:b] };
 
+    //===------------------------------------------------------------------===//
+    // Conditional operator
+
+    // CHECK: moore.conditional %x : i1 -> i32 {
+    // CHECK:   moore.yield %a : i32
+    // CHECK: } {
+    // CHECK:   moore.yield %b : i32
+    // CHECK: }
+    c = x ? a : b;
+
+    // CHECK: moore.conditional %x : i1 -> real {
+    // CHECK:   moore.yield %r1 : real
+    // CHECK: } {
+    // CHECK:   moore.yield %r2 : real
+    // CHECK: }
+    r1 = x ? r1 : r2;
+
+    // CHECK: [[TMP1:%.+]] = moore.bool_cast %a : i32 -> i1
+    // CHECK: moore.conditional [[TMP1]] : i1 -> i32 {
+    // CHECK:   moore.yield %a : i32
+    // CHECK: } {
+    // CHECK:   moore.yield %b : i32
+    // CHECK: }
+    c = a ? a : b;
+
+    // CHECK: [[TMP1:%.+]] = moore.sgt %a, %b : i32 -> i1
+    // CHECK: moore.conditional [[TMP1]] : i1 -> i32 {
+    // CHECK:   [[TMP2:%.+]] = moore.add %a, %b : i32
+    // CHECK:   moore.yield [[TMP2]] : i32
+    // CHECK: } {
+    // CHECK:   [[TMP2:%.+]] = moore.sub %a, %b : i32
+    // CHECK:   moore.yield [[TMP2]] : i32
+    // CHECK: }
+    c = (a > b) ? (a + b) : (a - b);
+
     //===------------------------------------------------------------------===//
     // Assign operators
 

test/Dialect/Moore/basic.mlir

@@ -217,4 +217,15 @@ moore.module @Expressions() {
   // CHECK: moore.extract [[VAL4]] from [[VAL5]] : i8, i32 -> i5
   %5 = moore.constant 2 : i32
   moore.extract %4 from %5 : i8, i32 -> i5
+
+  // CHECK: moore.conditional %b1 : i1 -> i32 {
+  // CHECK:   moore.yield %int : i32
+  // CHECK: } {
+  // CHECK:   moore.yield %int2 : i32
+  // CHECK: }
+  moore.conditional %b1 : i1 -> i32 {
+    moore.yield %int : i32
+  } {
+    moore.yield %int2 : i32
+  }
 }

test/Dialect/Moore/errors.mlir

@@ -65,3 +65,25 @@ moore.constant -2 : !moore.i1
 
 // expected-error @below {{attribute width 9 does not match return type's width 8}}
 "moore.constant" () {value = 42 : i9} : () -> !moore.i8
+
+// -----
+
+%y = moore.variable : i8
+
+moore.module @Cond() {
+  // expected-error @below {{'moore.yield' op expects parent op 'moore.conditional'}}
+  moore.yield %y : i8
+}
+
+// -----
+
+%x = moore.variable : i1
+%t = moore.variable : i8
+%f = moore.variable : i8
+
+moore.conditional %x : i1 -> i32 {
+  // expected-error @below {{yield type must match conditional. Expected '!moore.i32', but got '!moore.i8'}}
+  moore.yield %t : i8
+} {
+  moore.yield %f : i8
+}