Changeset 192531 in webkit

Timestamp:

Nov 17, 2015 1:55:33 PM (8 years ago)

Author:

mark.lam@apple.com

Message:

Use the JITAddGenerator snippet in the DFG.
​https://bugs.webkit.org/show_bug.cgi?id=151266

Reviewed by Geoffrey Garen.

No tests added because the op_add.js stress test already tests for correctness
(using the LLINT as a reference).

Performance-wise, the difference from the pre-existing DFG implementation is
insignificant (at least as measured on x86 and x86_64). We're moving forward
with adopting this implementation because it unifies the 32-bit and 64-bit
implementations, as well as lays ground work for a repatching inline cache
implementation of op_add later.

• dfg/DFGAbstractValue.cpp:

(JSC::DFG::AbstractValue::resultType):

• Made an assertion less restrictive. For ValueAdd operands, the DFG thinks that the operand can also be empty (though we should never see this in practice).

• dfg/DFGFixupPhase.cpp:

(JSC::DFG::FixupPhase::fixupNode):

• Add fallback to unused type operands.

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::compileValueAdd):

• Introduce a common function to compile the ValueAdd node.

• dfg/DFGSpeculativeJIT.h:

(JSC::DFG::JSValueOperand::JSValueOperand):

• Add the forwarding constructor so that we can use Optional<JSValueOperand>.

• dfg/DFGSpeculativeJIT32_64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• dfg/DFGSpeculativeJIT64.cpp:

(JSC::DFG::SpeculativeJIT::compile):

• Changed to use the common compileValueAdd().

• jit/AssemblyHelpers.h:

(JSC::AssemblyHelpers::moveValue):

• Similar to moveTrustedValue() but used for untrusted constants.

• jit/JITAddGenerator.cpp:

(JSC::JITAddGenerator::generateFastPath):

• jit/JITAddGenerator.h:

(JSC::JITAddGenerator::JITAddGenerator):

• Updated to take the left or right operand as a constant. This is necessary because the client should not be making assumptions about whether the snippet will determine the operation to be commutative or not. Instead, the client should just pass in the operands and let the snippet do any operand order swapping if necessary.

• jit/JITArithmetic.cpp:

(JSC::JIT::emit_op_add):

• Updated to use the new JITAddGenerator interface.

• tests/stress/op_add.js:

(stringifyIfNeeded):
(runTest):

• Made test output more clear about when string results are expected.

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• dfg/DFGAbstractValue.cpp (modified) (1 diff)
• dfg/DFGFixupPhase.cpp (modified) (1 diff)
• dfg/DFGSpeculativeJIT.cpp (modified) (2 diffs)
• dfg/DFGSpeculativeJIT.h (modified) (2 diffs)
• dfg/DFGSpeculativeJIT32_64.cpp (modified) (1 diff)
• dfg/DFGSpeculativeJIT64.cpp (modified) (1 diff)
• jit/AssemblyHelpers.h (modified) (1 diff)
• jit/JITAddGenerator.cpp (modified) (4 diffs)
• jit/JITAddGenerator.h (modified) (2 diffs)
• jit/JITArithmetic.cpp (modified) (1 diff)
• tests/stress/op_add.js (modified) (3 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2015-11-17  Mark Lam  <mark.lam@apple.com>
+
+        Use the JITAddGenerator snippet in the DFG.
+        https://bugs.webkit.org/show_bug.cgi?id=151266
+
+        Reviewed by Geoffrey Garen.
+
+        No tests added because the op_add.js stress test already tests for correctness
+        (using the LLINT as a reference).
+
+        Performance-wise, the difference from the pre-existing DFG implementation is
+        insignificant (at least as measured on x86 and x86_64).  We're moving forward
+        with adopting this implementation because it unifies the 32-bit and 64-bit
+        implementations, as well as lays ground work for a repatching inline cache
+        implementation of op_add later.
+
+        * dfg/DFGAbstractValue.cpp:
+        (JSC::DFG::AbstractValue::resultType):
+        - Made an assertion less restrictive.  For ValueAdd operands, the DFG thinks that
+          the operand can also be empty (though we should never see this in practice).
+
+        * dfg/DFGFixupPhase.cpp:
+        (JSC::DFG::FixupPhase::fixupNode):
+        - Add fallback to unused type operands.
+
+        * dfg/DFGSpeculativeJIT.cpp:
+        (JSC::DFG::SpeculativeJIT::compileValueAdd):
+        - Introduce a common function to compile the ValueAdd node.
+
+        * dfg/DFGSpeculativeJIT.h:
+        (JSC::DFG::JSValueOperand::JSValueOperand):
+        - Add the forwarding constructor so that we can use Optional<JSValueOperand>.
+
+        * dfg/DFGSpeculativeJIT32_64.cpp:
+        (JSC::DFG::SpeculativeJIT::compile):
+        * dfg/DFGSpeculativeJIT64.cpp:
+        (JSC::DFG::SpeculativeJIT::compile):
+        - Changed to use the common compileValueAdd().
+
+        * jit/AssemblyHelpers.h:
+        (JSC::AssemblyHelpers::moveValue):
+        - Similar to moveTrustedValue() but used for untrusted constants.
+
+        * jit/JITAddGenerator.cpp:
+        (JSC::JITAddGenerator::generateFastPath):
+        * jit/JITAddGenerator.h:
+        (JSC::JITAddGenerator::JITAddGenerator):
+        - Updated to take the left or right operand as a constant.  This is necessary
+          because the client should not be making assumptions about whether the snippet
+          will determine the operation to be commutative or not.  Instead, the client
+          should just pass in the operands and let the snippet do any operand order
+          swapping if necessary.
+
+        * jit/JITArithmetic.cpp:
+        (JSC::JIT::emit_op_add):
+        - Updated to use the new JITAddGenerator interface.
+
+        * tests/stress/op_add.js:
+        (stringifyIfNeeded):
+        (runTest):
+        - Made test output more clear about when string results are expected.
+
 2015-11-17  Filip Pizlo  <fpizlo@apple.com>
 

trunk/Source/JavaScriptCore/dfg/DFGAbstractValue.cpp

@@ -500 +500 @@
 ResultType AbstractValue::resultType() const
 {
-    ASSERT(isType(SpecHeapTop));
+    ASSERT(isType(SpecBytecodeTop));
     if (isType(SpecBoolean))
         return ResultType::booleanType();

trunk/Source/JavaScriptCore/dfg/DFGFixupPhase.cpp

@@ -156 +156 @@
                 break;
 
-            // We could attempt to turn this into a StrCat here. But for now, that wouldn't
-            // significantly reduce the number of branches required.
+            fixEdge<UntypedUse>(node->child1());
+            fixEdge<UntypedUse>(node->child2());
+            node->setResult(NodeResultJS);
             break;
         }

trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp

@@ -39 +39 @@
 #include "DFGSlowPathGenerator.h"
 #include "DirectArguments.h"
+#include "JITAddGenerator.h"
 #include "JITSubGenerator.h"
 #include "JSArrowFunction.h"
@@ -2781 +2782 @@
 
     blessedBooleanResult(scratchReg, node);
+}
+
+void SpeculativeJIT::compileValueAdd(Node* node)
+{
+    if (isKnownNotNumber(node->child1().node()) || isKnownNotNumber(node->child2().node())) {
+        JSValueOperand left(this, node->child1());
+        JSValueOperand right(this, node->child2());
+        JSValueRegs leftRegs = left.jsValueRegs();
+        JSValueRegs rightRegs = right.jsValueRegs();
+#if USE(JSVALUE64)
+        GPRTemporary result(this);
+        JSValueRegs resultRegs = JSValueRegs(result.gpr());
+#else
+        GPRTemporary resultTag(this);
+        GPRTemporary resultPayload(this);
+        JSValueRegs resultRegs = JSValueRegs(resultPayload.gpr(), resultTag.gpr());
+#endif
+        flushRegisters();
+        callOperation(operationValueAddNotNumber, resultRegs, leftRegs, rightRegs);
+        m_jit.exceptionCheck();
+    
+        jsValueResult(resultRegs, node);
+        return;
+    }
+
+    bool leftIsConstInt32 = node->child1()->isInt32Constant();
+    bool rightIsConstInt32 = node->child2()->isInt32Constant();
+
+    // The DFG does not always fold the sum of 2 constant int operands together.
+    if (leftIsConstInt32 && rightIsConstInt32) {
+#if USE(JSVALUE64)
+        GPRTemporary result(this);
+        JSValueRegs resultRegs = JSValueRegs(result.gpr());
+#else
+        GPRTemporary resultTag(this);
+        GPRTemporary resultPayload(this);
+        JSValueRegs resultRegs = JSValueRegs(resultPayload.gpr(), resultTag.gpr());
+#endif
+        int64_t leftConst = node->child1()->asInt32();
+        int64_t rightConst = node->child2()->asInt32();
+        int64_t resultConst = leftConst + rightConst;
+        m_jit.moveValue(JSValue(resultConst), resultRegs);
+        jsValueResult(resultRegs, node);
+        return;
+    }
+
+    Optional<JSValueOperand> left;
+    Optional<JSValueOperand> right;
+
+    JSValueRegs leftRegs;
+    JSValueRegs rightRegs;
+
+    FPRTemporary leftNumber(this);
+    FPRTemporary rightNumber(this);
+    FPRReg leftFPR = leftNumber.fpr();
+    FPRReg rightFPR = rightNumber.fpr();
+
+#if USE(JSVALUE64)
+    GPRTemporary result(this);
+    JSValueRegs resultRegs = JSValueRegs(result.gpr());
+    GPRTemporary scratch(this);
+    GPRReg scratchGPR = scratch.gpr();
+    FPRReg scratchFPR = InvalidFPRReg;
+#else
+    GPRTemporary resultTag(this);
+    GPRTemporary resultPayload(this);
+    JSValueRegs resultRegs = JSValueRegs(resultPayload.gpr(), resultTag.gpr());
+    GPRReg scratchGPR = resultTag.gpr();
+    FPRTemporary fprScratch(this);
+    FPRReg scratchFPR = fprScratch.fpr();
+#endif
+
+    ResultType leftType = m_state.forNode(node->child1()).resultType();
+    ResultType rightType = m_state.forNode(node->child2()).resultType();
+    int32_t leftConstInt32 = 0;
+    int32_t rightConstInt32 = 0;
+
+    ASSERT(!leftIsConstInt32 || !rightIsConstInt32);
+
+    if (leftIsConstInt32) {
+        leftConstInt32 = node->child1()->asInt32();
+        right = JSValueOperand(this, node->child2());
+        rightRegs = right->jsValueRegs();
+    } else if (rightIsConstInt32) {
+        left = JSValueOperand(this, node->child1());
+        leftRegs = left->jsValueRegs();
+        rightConstInt32 = node->child2()->asInt32();
+    } else {
+        left = JSValueOperand(this, node->child1());
+        leftRegs = left->jsValueRegs();
+        right = JSValueOperand(this, node->child2());
+        rightRegs = right->jsValueRegs();
+    }
+
+    JITAddGenerator gen(resultRegs, leftRegs, rightRegs, leftType, rightType,
+        leftIsConstInt32, rightIsConstInt32, leftConstInt32, rightConstInt32,
+        leftFPR, rightFPR, scratchGPR, scratchFPR);
+    gen.generateFastPath(m_jit);
+
+    gen.slowPathJumpList().link(&m_jit);
+
+    silentSpillAllRegisters(resultRegs);
+
+    if (leftIsConstInt32) {
+        leftRegs = resultRegs;
+        int64_t leftConst = node->child1()->asInt32();
+        m_jit.moveValue(JSValue(leftConst), leftRegs);
+    } else if (rightIsConstInt32) {
+        rightRegs = resultRegs;
+        int64_t rightConst = node->child2()->asInt32();
+        m_jit.moveValue(JSValue(rightConst), rightRegs);
+    }
+
+    callOperation(operationValueAdd, resultRegs, leftRegs, rightRegs);
+
+    silentFillAllRegisters(resultRegs);
+    m_jit.exceptionCheck();
+
+    gen.endJumpList().link(&m_jit);
+    jsValueResult(resultRegs, node);
+    return;
 }
 

trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.h

@@ -2208 +2208 @@
     void compileUInt32ToNumber(Node*);
     void compileDoubleAsInt32(Node*);
+    void compileValueAdd(Node*);
     void compileArithAdd(Node*);
     void compileMakeRope(Node*);
@@ -2553 +2554 @@
     }
 
+    explicit JSValueOperand(JSValueOperand&& other)
+        : m_jit(other.m_jit)
+        , m_edge(other.m_edge)
+    {
+#if USE(JSVALUE64)
+        m_gprOrInvalid = other.m_gprOrInvalid;
+#elif USE(JSVALUE32_64)
+        m_register.pair.tagGPR = InvalidGPRReg;
+        m_register.pair.payloadGPR = InvalidGPRReg;
+        m_isDouble = other.m_isDouble;
+
+        if (m_edge) {
+            if (m_isDouble)
+                m_register.fpr = other.m_register.fpr;
+            else
+                m_register.pair = other.m_register.pair;
+        }
+#endif
+        other.m_edge = Edge();
+#if USE(JSVALUE64)
+        other.m_gprOrInvalid = InvalidGPRReg;
+#elif USE(JSVALUE32_64)
+        other.m_isDouble = false;
+#endif
+    }
+
     ~JSValueOperand()
     {

trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT32_64.cpp

@@ -2135 +2135 @@
         break;
     }
-        
-    case ValueAdd: {
-        JSValueOperand op1(this, node->child1());
-        JSValueOperand op2(this, node->child2());
-        
-        GPRReg op1TagGPR = op1.tagGPR();
-        GPRReg op1PayloadGPR = op1.payloadGPR();
-        GPRReg op2TagGPR = op2.tagGPR();
-        GPRReg op2PayloadGPR = op2.payloadGPR();
-        
-        flushRegisters();
-        
-        GPRFlushedCallResult2 resultTag(this);
-        GPRFlushedCallResult resultPayload(this);
-        if (isKnownNotNumber(node->child1().node()) || isKnownNotNumber(node->child2().node()))
-            callOperation(operationValueAddNotNumber, resultTag.gpr(), resultPayload.gpr(), op1TagGPR, op1PayloadGPR, op2TagGPR, op2PayloadGPR);
-        else
-            callOperation(operationValueAdd, resultTag.gpr(), resultPayload.gpr(), op1TagGPR, op1PayloadGPR, op2TagGPR, op2PayloadGPR);
-        m_jit.exceptionCheck();
-        
-        jsValueResult(resultTag.gpr(), resultPayload.gpr(), node);
-        break;
-    }
+
+    case ValueAdd:
+        compileValueAdd(node);
+        break;
 
     case StrCat: {

trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp

@@ -2269 +2269 @@
         break;
     }
-        
-    case ValueAdd: {
-        JSValueOperand op1(this, node->child1());
-        JSValueOperand op2(this, node->child2());
-        
-        GPRReg op1GPR = op1.gpr();
-        GPRReg op2GPR = op2.gpr();
-        
-        flushRegisters();
-        
-        GPRFlushedCallResult result(this);
-        if (isKnownNotNumber(node->child1().node()) || isKnownNotNumber(node->child2().node()))
-            callOperation(operationValueAddNotNumber, result.gpr(), op1GPR, op2GPR);
-        else
-            callOperation(operationValueAdd, result.gpr(), op1GPR, op2GPR);
-        m_jit.exceptionCheck();
-        
-        jsValueResult(result.gpr(), node);
-        break;
-    }
-        
+
+    case ValueAdd:
+        compileValueAdd(node);
+        break;
+
     case StrCat: {
         JSValueOperand op1(this, node->child1(), ManualOperandSpeculation);

trunk/Source/JavaScriptCore/jit/AssemblyHelpers.h

@@ -149 +149 @@
 #endif
     }
-    
+
+    void moveValue(JSValue value, JSValueRegs regs)
+    {
+#if USE(JSVALUE64)
+        move(Imm64(JSValue::encode(value)), regs.gpr());
+#else
+        move(Imm32(value.tag()), regs.tagGPR());
+        move(Imm32(value.payload()), regs.payloadGPR());
+#endif
+    }
+
     void moveTrustedValue(JSValue value, JSValueRegs regs)
     {

trunk/Source/JavaScriptCore/jit/JITAddGenerator.cpp

@@ -36 +36 @@
     ASSERT(m_scratchGPR != m_left.payloadGPR());
     ASSERT(m_scratchGPR != m_right.payloadGPR());
-#if ENABLE(JSVALUE32_64)
-    ASSERT(m_scratchGPR != m_left.tagGPR());x
+#if USE(JSVALUE32_64)
+    ASSERT(m_scratchGPR != m_left.tagGPR());
     ASSERT(m_scratchGPR != m_right.tagGPR());
     ASSERT(m_scratchFPR != InvalidFPRReg);
 #endif
 
+    ASSERT(!m_leftIsConstInt32 || !m_rightIsConstInt32);
+    
     if (!m_leftType.mightBeNumber() || !m_rightType.mightBeNumber()) {
         m_slowPathJumpList.append(jit.jump());
@@ -47 +49 @@
     }
 
-    if (m_operandsConstness == RightIsConstInt32) {
+    if (m_leftIsConstInt32 || m_rightIsConstInt32) {
+        JSValueRegs var;
+        ResultType varType = ResultType::unknownType();
+        int32_t constInt32;
+
+        if (m_leftIsConstInt32) {
+            var = m_right;
+            varType = m_rightType;
+            constInt32 = m_leftConstInt32;
+        } else {
+            var = m_left;
+            varType = m_leftType;
+            constInt32 = m_rightConstInt32;
+        }
+
         // Try to do intVar + intConstant.
-        CCallHelpers::Jump notInt32 = jit.branchIfNotInt32(m_left);
+        CCallHelpers::Jump notInt32 = jit.branchIfNotInt32(var);
 
-        m_slowPathJumpList.append(jit.branchAdd32(CCallHelpers::Overflow, m_left.payloadGPR(), CCallHelpers::Imm32(m_rightConstInt32), m_scratchGPR));
+        m_slowPathJumpList.append(jit.branchAdd32(CCallHelpers::Overflow, var.payloadGPR(), CCallHelpers::Imm32(constInt32), m_scratchGPR));
 
         jit.boxInt32(m_scratchGPR, m_result);
@@ -63 +79 @@
         // Try to do doubleVar + double(intConstant).
         notInt32.link(&jit);
-        if (!m_leftType.definitelyIsNumber())
-            m_slowPathJumpList.append(jit.branchIfNotNumber(m_left, m_scratchGPR));
+        if (!varType.definitelyIsNumber())
+            m_slowPathJumpList.append(jit.branchIfNotNumber(var, m_scratchGPR));
 
-        jit.unboxDoubleNonDestructive(m_left, m_leftFPR, m_scratchGPR, m_scratchFPR);
+        jit.unboxDoubleNonDestructive(var, m_leftFPR, m_scratchGPR, m_scratchFPR);
 
-        jit.move(CCallHelpers::Imm32(m_rightConstInt32), m_scratchGPR);
+        jit.move(CCallHelpers::Imm32(constInt32), m_scratchGPR);
         jit.convertInt32ToDouble(m_scratchGPR, m_rightFPR);
 
@@ -74 +90 @@
 
     } else {
-        ASSERT(m_operandsConstness == NeitherAreConstInt32);
+        ASSERT(!m_leftIsConstInt32 && !m_rightIsConstInt32);
         CCallHelpers::Jump leftNotInt;
         CCallHelpers::Jump rightNotInt;

trunk/Source/JavaScriptCore/jit/JITAddGenerator.h

@@ -36 +36 @@
 class JITAddGenerator {
 public:
-    enum OperandsConstness {
-        NeitherAreConstInt32,
-
-        // Since addition is commutative, it doesn't matter which operand we make the
-        // ConstInt32. Let's always put the const in the right, and the variable operand
-        // in the left.
-        RightIsConstInt32,
-
-        // We choose not to implement any optimization for the case where both operands
-        // are ConstInt32 here. The client may choose to do that optimzation and not
-        // invoke this snippet generator, or may load both operands into registers
-        // and pass them as variables to the snippet generator instead.
-    };
-
     JITAddGenerator(JSValueRegs result, JSValueRegs left, JSValueRegs right,
-        OperandsConstness operandsConstness, int32_t rightConstInt32,
-        ResultType leftType, ResultType rightType, FPRReg leftFPR, FPRReg rightFPR,
+        ResultType leftType, ResultType rightType, bool leftIsConstInt32, bool rightIsConstInt32,
+        int32_t leftConstInt32, int32_t rightConstInt32, FPRReg leftFPR, FPRReg rightFPR,
         GPRReg scratchGPR, FPRReg scratchFPR)
         : m_result(result)
         , m_left(left)
         , m_right(right)
-        , m_operandsConstness(operandsConstness)
-        , m_rightConstInt32(rightConstInt32)
         , m_leftType(leftType)
         , m_rightType(rightType)
+        , m_leftIsConstInt32(leftIsConstInt32)
+        , m_rightIsConstInt32(rightIsConstInt32)
+        , m_leftConstInt32(leftConstInt32)
+        , m_rightConstInt32(rightConstInt32)
         , m_leftFPR(leftFPR)
         , m_rightFPR(rightFPR)
         , m_scratchGPR(scratchGPR)
         , m_scratchFPR(scratchFPR)
-    { }
+    {
+        ASSERT(!leftIsConstInt32 || !rightIsConstInt32);
+    }
 
     void generateFastPath(CCallHelpers&);
@@ -76 +66 @@
     JSValueRegs m_left;
     JSValueRegs m_right;
-    OperandsConstness m_operandsConstness;
-    int32_t m_rightConstInt32;
     ResultType m_leftType;
     ResultType m_rightType;
+    bool m_leftIsConstInt32;
+    bool m_rightIsConstInt32;
+    int32_t m_leftConstInt32;
+    int32_t m_rightConstInt32;
     FPRReg m_leftFPR;
     FPRReg m_rightFPR;

trunk/Source/JavaScriptCore/jit/JITArithmetic.cpp

@@ -935 +935 @@
     bool leftIsConstInt32 = isOperandConstantInt(op1);
     bool rightIsConstInt32 = isOperandConstantInt(op2);
-    JITAddGenerator::OperandsConstness operandsConstness;
-    int32_t rightConstInt32 = 0;
     ResultType leftType = types.first();
     ResultType rightType = types.second();
+    int32_t leftConstInt32 = 0;
+    int32_t rightConstInt32 = 0;
 
     ASSERT(!leftIsConstInt32 || !rightIsConstInt32);
 
     if (leftIsConstInt32) {
-        // JITAddGenerator expects the const value in the right operand.
-        // Let's swap the operands.
-        operandsConstness = JITAddGenerator::RightIsConstInt32;
-        rightConstInt32 = getOperandConstantInt(op1);
-        rightType = types.first();
-        emitGetVirtualRegister(op2, leftRegs);
-        leftType = types.second();
+        leftConstInt32 = getOperandConstantInt(op1);
+        emitGetVirtualRegister(op2, rightRegs);
     } else if (rightIsConstInt32) {
-        operandsConstness = JITAddGenerator::RightIsConstInt32;
+        emitGetVirtualRegister(op1, leftRegs);
         rightConstInt32 = getOperandConstantInt(op2);
-        emitGetVirtualRegister(op1, leftRegs);
-    } else {
-        operandsConstness = JITAddGenerator::NeitherAreConstInt32;
+    } else {
         emitGetVirtualRegister(op1, leftRegs);
         emitGetVirtualRegister(op2, rightRegs);
     }
 
-    JITAddGenerator gen(resultRegs, leftRegs, rightRegs,
-        operandsConstness, rightConstInt32,
-        leftType, rightType,
+    JITAddGenerator gen(resultRegs, leftRegs, rightRegs, leftType, rightType,
+        leftIsConstInt32, rightIsConstInt32, leftConstInt32, rightConstInt32,
         fpRegT0, fpRegT1, scratchGPR, scratchFPR);
 

trunk/Source/JavaScriptCore/tests/stress/op_add.js

@@ -319 +319 @@
 var errorReport = "";
 
+function stringifyIfNeeded(x) {
+    if (typeof x == "string")
+        return '"' + x + '"';
+    return x;
+}
+
 function runTest(test) {
     var failedScenario = [];
@@ -328 +334 @@
                 var scenario = scenarios[scenarioID];
                 if (verbose)
-                    print("Testing " + test.name + ":" + scenario.name + " on iteration " + i + ": expecting " + scenario.expected); 
+                    print("Testing " + test.name + ":" + scenario.name + " on iteration " + i + ": expecting " + stringifyIfNeeded(scenario.expected)); 
 
                 var result = testFunc(scenario.x, scenario.y);
@@ -336 +342 @@
                     continue;
                 if (!failedScenario[scenarioID]) {
-                    errorReport += "FAIL: " + test.name + ":" + scenario.name + " started failing on iteration " + i + ": expected " + scenario.expected + ", actual " + result + "\n";
+                    errorReport += "FAIL: " + test.name + ":" + scenario.name + " started failing on iteration " + i
+                        + ": expected " + stringifyIfNeeded(scenario.expected) + ", actual " + stringifyIfNeeded(result) + "\n";
                     if (abortOnFirstFail)
                         throw errorReport;