wasm: Add support for pattern matching on composites

These changes add basic support for pattern matching on arrays and
objects. Sets and comprehensions not supported yet.

Also, as part of these changes, remove the opa_value_not_equal
function as it's unnecessary given opa_value_compare.

ref open-policy-agent#1113

Signed-off-by: Torin Sandall <torinsandall@gmail.com>

internal/compiler/wasm/wasm.go

@@ -20,17 +20,29 @@ import (
 )
 
 const (
-	opaFuncPrefix       = "opa_"
-	opaJSONParse        = "opa_json_parse"
-	opaNull             = "opa_null"
-	opaBoolean          = "opa_boolean"
-	opaStringTerminated = "opa_string_terminated"
-	opaNumberInt        = "opa_number_int"
-	opaValueBooleanSet  = "opa_value_boolean_set"
-	opaValueNotEqual    = "opa_value_not_equal"
-	opaValueCompare     = "opa_value_compare"
-	opaValueGet         = "opa_value_get"
-	opaValueIter        = "opa_value_iter"
+	opaTypeNull int32 = iota + 1
+	opaTypeBoolean
+	opaTypeNumber
+	opaTypeString
+	opaTypeArray
+	opaTypeObject
+)
+
+const (
+	opaFuncPrefix        = "opa_"
+	opaJSONParse         = "opa_json_parse"
+	opaNull              = "opa_null"
+	opaBoolean           = "opa_boolean"
+	opaStringTerminated  = "opa_string_terminated"
+	opaNumberInt         = "opa_number_int"
+	opaNumberSize        = "opa_number_size"
+	opaValueBooleanSet   = "opa_value_boolean_set"
+	opaValueNumberSetInt = "opa_value_number_set_int"
+	opaValueCompare      = "opa_value_compare"
+	opaValueGet          = "opa_value_get"
+	opaValueIter         = "opa_value_iter"
+	opaValueLength       = "opa_value_length"
+	opaValueType         = "opa_value_type"
 )
 
 // Compiler implements an IR->WASM compiler backend.
@@ -165,6 +177,9 @@ func (c *Compiler) compileBlock(block ir.Block) ([]instruction.Instruction, erro
 		case ir.ReturnStmt:
 			instrs = append(instrs, instruction.I32Const{Value: int32(stmt.Code)})
 			instrs = append(instrs, instruction.Return{})
+		case ir.AssignVarStmt:
+			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Source)})
+			instrs = append(instrs, instruction.SetLocal{Index: c.local(stmt.Target)})
 		case ir.AssignBooleanStmt:
 			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Target)})
 			if stmt.Value {
@@ -173,6 +188,10 @@ func (c *Compiler) compileBlock(block ir.Block) ([]instruction.Instruction, erro
 				instrs = append(instrs, instruction.I32Const{Value: 0})
 			}
 			instrs = append(instrs, instruction.Call{Index: c.function(opaValueBooleanSet)})
+		case ir.AssignIntStmt:
+			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Target)})
+			instrs = append(instrs, instruction.I64Const{Value: stmt.Value})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaValueNumberSetInt)})
 		case ir.ScanStmt:
 			if err := c.compileScan(stmt, &instrs); err != nil {
 				return nil, err
@@ -189,10 +208,15 @@ func (c *Compiler) compileBlock(block ir.Block) ([]instruction.Instruction, erro
 			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Target)})
 			instrs = append(instrs, instruction.I32Eqz{})
 			instrs = append(instrs, instruction.BrIf{Index: 0})
+		case ir.LenStmt:
+			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Source)})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaValueLength)})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaNumberSize)})
+			instrs = append(instrs, instruction.SetLocal{Index: c.local(stmt.Target)})
 		case ir.EqualStmt:
 			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.A)})
 			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.B)})
-			instrs = append(instrs, instruction.Call{Index: c.function(opaValueNotEqual)})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaValueCompare)})
 			instrs = append(instrs, instruction.BrIf{Index: 0})
 		case ir.LessThanStmt:
 			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.A)})
@@ -249,6 +273,18 @@ func (c *Compiler) compileBlock(block ir.Block) ([]instruction.Instruction, erro
 			instrs = append(instrs, instruction.I32Const{Value: c.stringAddr(stmt.Index)})
 			instrs = append(instrs, instruction.Call{Index: c.function(opaStringTerminated)})
 			instrs = append(instrs, instruction.SetLocal{Index: c.local(stmt.Target)})
+		case ir.IsArrayStmt:
+			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Source)})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaValueType)})
+			instrs = append(instrs, instruction.I32Const{Value: opaTypeArray})
+			instrs = append(instrs, instruction.I32Ne{})
+			instrs = append(instrs, instruction.BrIf{Index: 0})
+		case ir.IsObjectStmt:
+			instrs = append(instrs, instruction.GetLocal{Index: c.local(stmt.Source)})
+			instrs = append(instrs, instruction.Call{Index: c.function(opaValueType)})
+			instrs = append(instrs, instruction.I32Const{Value: opaTypeObject})
+			instrs = append(instrs, instruction.I32Ne{})
+			instrs = append(instrs, instruction.BrIf{Index: 0})
 		default:
 			var buf bytes.Buffer
 			ir.Pretty(&buf, stmt)

internal/ir/ir.go

@@ -137,6 +137,13 @@ type DotStmt struct {
 	Target Local
 }
 
+// LenStmt represents a length() operation on a local variable. The
+// result is stored in the target local variable.
+type LenStmt struct {
+	Source Local
+	Target Local
+}
+
 // ScanStmt represents a linear scan over a composite value. The
 // source may be a scalar in which case the block will never execute.
 type ScanStmt struct {
@@ -159,6 +166,19 @@ type AssignBooleanStmt struct {
 	Target Local
 }
 
+// AssignIntStmt represents an assignment of an integer value to a
+// local variable.
+type AssignIntStmt struct {
+	Value  int64
+	Target Local
+}
+
+// AssignVarStmt represents an assignment of one local variable to another.
+type AssignVarStmt struct {
+	Source Local
+	Target Local
+}
+
 // MakeStringStmt constructs a local variable that refers to a string constant.
 type MakeStringStmt struct {
 	Index  int
@@ -217,3 +237,13 @@ type NotEqualStmt struct {
 	A Local
 	B Local
 }
+
+// IsArrayStmt represents a dynamic type check on a local variable.
+type IsArrayStmt struct {
+	Source Local
+}
+
+// IsObjectStmt represents a dynamic type check on a local variable.
+type IsObjectStmt struct {
+	Source Local
+}