Add generated code to calculate Math.log and to search Transcendental cache for logs. Implemented on all platforms.

Review URL: http://codereview.chromium.org/5437002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5912 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/code-stubs-arm.cc

@@ -2290,6 +2290,7 @@ Runtime::FunctionId TranscendentalCacheStub::RuntimeFunction() {
     // Add more cases when necessary.
     case TranscendentalCache::SIN: return Runtime::kMath_sin;
     case TranscendentalCache::COS: return Runtime::kMath_cos;
+    case TranscendentalCache::LOG: return Runtime::kMath_log;
     default:
       UNIMPLEMENTED();
       return Runtime::kAbort;

src/arm/codegen-arm.cc

@@ -5750,6 +5750,20 @@ void CodeGenerator::GenerateMathCos(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateMathLog(ZoneList<Expression*>* args) {
+  ASSERT_EQ(args->length(), 1);
+  Load(args->at(0));
+  if (CpuFeatures::IsSupported(VFP3)) {
+    TranscendentalCacheStub stub(TranscendentalCache::LOG);
+    frame_->SpillAllButCopyTOSToR0();
+    frame_->CallStub(&stub, 1);
+  } else {
+    frame_->CallRuntime(Runtime::kMath_log, 1);
+  }
+  frame_->EmitPush(r0);
+}
+
+
 void CodeGenerator::GenerateObjectEquals(ZoneList<Expression*>* args) {
   ASSERT(args->length() == 2);
 

src/arm/codegen-arm.h

@@ -516,6 +516,7 @@ class CodeGenerator: public AstVisitor {
   void GenerateMathSin(ZoneList<Expression*>* args);
   void GenerateMathCos(ZoneList<Expression*>* args);
   void GenerateMathSqrt(ZoneList<Expression*>* args);
+  void GenerateMathLog(ZoneList<Expression*>* args);
 
   void GenerateIsRegExpEquivalent(ZoneList<Expression*>* args);
 

src/arm/full-codegen-arm.cc

@@ -2617,6 +2617,15 @@ void FullCodeGenerator::EmitMathSqrt(ZoneList<Expression*>* args) {
 }
 
 
+void FullCodeGenerator::EmitMathLog(ZoneList<Expression*>* args) {
+  // Load the argument on the stack and call the runtime function.
+  ASSERT(args->length() == 1);
+  VisitForStackValue(args->at(0));
+  __ CallRuntime(Runtime::kMath_log, 1);
+  context()->Plug(r0);
+}
+
+
 void FullCodeGenerator::EmitCallFunction(ZoneList<Expression*>* args) {
   ASSERT(args->length() >= 2);
 

src/ia32/assembler-ia32.cc

@@ -1772,6 +1772,14 @@ void Assembler::fldz() {
 }
 
 
+void Assembler::fldln2() {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  EMIT(0xD9);
+  EMIT(0xED);
+}
+
+
 void Assembler::fld_s(const Operand& adr) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
@@ -1902,6 +1910,14 @@ void Assembler::fsin() {
 }
 
 
+void Assembler::fyl2x() {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  EMIT(0xD9);
+  EMIT(0xF1);
+}
+
+
 void Assembler::fadd(int i) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;

src/ia32/assembler-ia32.h

@@ -720,6 +720,7 @@ class Assembler : public Malloced {
   void fld1();
   void fldz();
   void fldpi();
+  void fldln2();
 
   void fld_s(const Operand& adr);
   void fld_d(const Operand& adr);
@@ -744,6 +745,7 @@ class Assembler : public Malloced {
   void fchs();
   void fcos();
   void fsin();
+  void fyl2x();
 
   void fadd(int i);
   void fsub(int i);

src/ia32/code-stubs-ia32.cc

@@ -1330,6 +1330,7 @@ Runtime::FunctionId TranscendentalCacheStub::RuntimeFunction() {
     // Add more cases when necessary.
     case TranscendentalCache::SIN: return Runtime::kMath_sin;
     case TranscendentalCache::COS: return Runtime::kMath_cos;
+    case TranscendentalCache::LOG: return Runtime::kMath_log;
     default:
       UNIMPLEMENTED();
       return Runtime::kAbort;
@@ -1339,85 +1340,90 @@ Runtime::FunctionId TranscendentalCacheStub::RuntimeFunction() {
 
 void TranscendentalCacheStub::GenerateOperation(MacroAssembler* masm) {
   // Only free register is edi.
+  // Input value is on FP stack, and also in ebx/edx.  Address of result
+  // (a newly allocated HeapNumber) is in eax.
   NearLabel done;
-  ASSERT(type_ == TranscendentalCache::SIN ||
-         type_ == TranscendentalCache::COS);
-  // More transcendental types can be added later.
+  if (type_ == TranscendentalCache::SIN || type_ == TranscendentalCache::COS) {
+    // Both fsin and fcos require arguments in the range +/-2^63 and
+    // return NaN for infinities and NaN. They can share all code except
+    // the actual fsin/fcos operation.
+    NearLabel in_range;
+    // If argument is outside the range -2^63..2^63, fsin/cos doesn't
+    // work. We must reduce it to the appropriate range.
+    __ mov(edi, edx);
+    __ and_(Operand(edi), Immediate(0x7ff00000));  // Exponent only.
+    int supported_exponent_limit =
+        (63 + HeapNumber::kExponentBias) << HeapNumber::kExponentShift;
+    __ cmp(Operand(edi), Immediate(supported_exponent_limit));
+    __ j(below, &in_range, taken);
+    // Check for infinity and NaN. Both return NaN for sin.
+    __ cmp(Operand(edi), Immediate(0x7ff00000));
+    NearLabel non_nan_result;
+    __ j(not_equal, &non_nan_result, taken);
+    // Input is +/-Infinity or NaN. Result is NaN.
+    __ fstp(0);
+    // NaN is represented by 0x7ff8000000000000.
+    __ push(Immediate(0x7ff80000));
+    __ push(Immediate(0));
+    __ fld_d(Operand(esp, 0));
+    __ add(Operand(esp), Immediate(2 * kPointerSize));
+    __ jmp(&done);
 
-  // Both fsin and fcos require arguments in the range +/-2^63 and
-  // return NaN for infinities and NaN. They can share all code except
-  // the actual fsin/fcos operation.
-  NearLabel in_range;
-  // If argument is outside the range -2^63..2^63, fsin/cos doesn't
-  // work. We must reduce it to the appropriate range.
-  __ mov(edi, edx);
-  __ and_(Operand(edi), Immediate(0x7ff00000));  // Exponent only.
-  int supported_exponent_limit =
-      (63 + HeapNumber::kExponentBias) << HeapNumber::kExponentShift;
-  __ cmp(Operand(edi), Immediate(supported_exponent_limit));
-  __ j(below, &in_range, taken);
-  // Check for infinity and NaN. Both return NaN for sin.
-  __ cmp(Operand(edi), Immediate(0x7ff00000));
-  NearLabel non_nan_result;
-  __ j(not_equal, &non_nan_result, taken);
-  // Input is +/-Infinity or NaN. Result is NaN.
-  __ fstp(0);
-  // NaN is represented by 0x7ff8000000000000.
-  __ push(Immediate(0x7ff80000));
-  __ push(Immediate(0));
-  __ fld_d(Operand(esp, 0));
-  __ add(Operand(esp), Immediate(2 * kPointerSize));
-  __ jmp(&done);
+    __ bind(&non_nan_result);
 
-  __ bind(&non_nan_result);
+    // Use fpmod to restrict argument to the range +/-2*PI.
+    __ mov(edi, eax);  // Save eax before using fnstsw_ax.
+    __ fldpi();
+    __ fadd(0);
+    __ fld(1);
+    // FPU Stack: input, 2*pi, input.
+    {
+      NearLabel no_exceptions;
+      __ fwait();
+      __ fnstsw_ax();
+      // Clear if Illegal Operand or Zero Division exceptions are set.
+      __ test(Operand(eax), Immediate(5));
+      __ j(zero, &no_exceptions);
+      __ fnclex();
+      __ bind(&no_exceptions);
+    }
 
-  // Use fpmod to restrict argument to the range +/-2*PI.
-  __ mov(edi, eax);  // Save eax before using fnstsw_ax.
-  __ fldpi();
-  __ fadd(0);
-  __ fld(1);
-  // FPU Stack: input, 2*pi, input.
-  {
-    NearLabel no_exceptions;
-    __ fwait();
-    __ fnstsw_ax();
-    // Clear if Illegal Operand or Zero Division exceptions are set.
-    __ test(Operand(eax), Immediate(5));
-    __ j(zero, &no_exceptions);
-    __ fnclex();
-    __ bind(&no_exceptions);
+    // Compute st(0) % st(1)
+    {
+      NearLabel partial_remainder_loop;
+      __ bind(&partial_remainder_loop);
+      __ fprem1();
+      __ fwait();
+      __ fnstsw_ax();
+      __ test(Operand(eax), Immediate(0x400 /* C2 */));
+      // If C2 is set, computation only has partial result. Loop to
+      // continue computation.
+      __ j(not_zero, &partial_remainder_loop);
+    }
+    // FPU Stack: input, 2*pi, input % 2*pi
+    __ fstp(2);
+    __ fstp(0);
+    __ mov(eax, edi);  // Restore eax (allocated HeapNumber pointer).
+
+    // FPU Stack: input % 2*pi
+    __ bind(&in_range);
+    switch (type_) {
+      case TranscendentalCache::SIN:
+        __ fsin();
+        break;
+      case TranscendentalCache::COS:
+        __ fcos();
+        break;
+      default:
+        UNREACHABLE();
+    }
+    __ bind(&done);
+  } else {
+    ASSERT(type_ == TranscendentalCache::LOG);
+    __ fldln2();
+    __ fxch();
+    __ fyl2x();
   }
-
-  // Compute st(0) % st(1)
-  {
-    NearLabel partial_remainder_loop;
-    __ bind(&partial_remainder_loop);
-    __ fprem1();
-    __ fwait();
-    __ fnstsw_ax();
-    __ test(Operand(eax), Immediate(0x400 /* C2 */));
-    // If C2 is set, computation only has partial result. Loop to
-    // continue computation.
-    __ j(not_zero, &partial_remainder_loop);
-  }
-  // FPU Stack: input, 2*pi, input % 2*pi
-  __ fstp(2);
-  __ fstp(0);
-  __ mov(eax, edi);  // Restore eax (allocated HeapNumber pointer).
-
-  // FPU Stack: input % 2*pi
-  __ bind(&in_range);
-  switch (type_) {
-    case TranscendentalCache::SIN:
-      __ fsin();
-      break;
-    case TranscendentalCache::COS:
-      __ fcos();
-      break;
-    default:
-      UNREACHABLE();
-  }
-  __ bind(&done);
 }
 
 

src/ia32/codegen-ia32.cc

@@ -7995,6 +7995,15 @@ void CodeGenerator::GenerateMathCos(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateMathLog(ZoneList<Expression*>* args) {
+  ASSERT_EQ(args->length(), 1);
+  Load(args->at(0));
+  TranscendentalCacheStub stub(TranscendentalCache::LOG);
+  Result result = frame_->CallStub(&stub, 1);
+  frame_->Push(&result);
+}
+
+
 // Generates the Math.sqrt method. Please note - this function assumes that
 // the callsite has executed ToNumber on the argument.
 void CodeGenerator::GenerateMathSqrt(ZoneList<Expression*>* args) {

src/ia32/codegen-ia32.h

@@ -705,8 +705,9 @@ class CodeGenerator: public AstVisitor {
   void GenerateMathSin(ZoneList<Expression*>* args);
   void GenerateMathCos(ZoneList<Expression*>* args);
   void GenerateMathSqrt(ZoneList<Expression*>* args);
+  void GenerateMathLog(ZoneList<Expression*>* args);
 
-  // Check whether two RegExps are equivalent
+  // Check whether two RegExps are equivalent.
   void GenerateIsRegExpEquivalent(ZoneList<Expression*>* args);
 
   void GenerateHasCachedArrayIndex(ZoneList<Expression*>* args);

src/ia32/disasm-ia32.cc

@@ -733,7 +733,9 @@ int DisassemblerIA32::RegisterFPUInstruction(int escape_opcode,
             case 0xE4: mnem = "ftst"; break;
             case 0xE8: mnem = "fld1"; break;
             case 0xEB: mnem = "fldpi"; break;
+            case 0xED: mnem = "fldln2"; break;
             case 0xEE: mnem = "fldz"; break;
+            case 0xF1: mnem = "fyl2x"; break;
             case 0xF5: mnem = "fprem1"; break;
             case 0xF7: mnem = "fincstp"; break;
             case 0xF8: mnem = "fprem"; break;

src/ia32/full-codegen-ia32.cc

@@ -2917,6 +2917,16 @@ void FullCodeGenerator::EmitMathCos(ZoneList<Expression*>* args) {
 }
 
 
+void FullCodeGenerator::EmitMathLog(ZoneList<Expression*>* args) {
+  // Load the argument on the stack and call the stub.
+  TranscendentalCacheStub stub(TranscendentalCache::LOG);
+  ASSERT(args->length() == 1);
+  VisitForStackValue(args->at(0));
+  __ CallStub(&stub);
+  context()->Plug(eax);
+}
+
+
 void FullCodeGenerator::EmitMathSqrt(ZoneList<Expression*>* args) {
   // Load the argument on the stack and call the runtime function.
   ASSERT(args->length() == 1);

src/math.js

@@ -113,7 +113,7 @@ function MathFloor(x) {
 // ECMA 262 - 15.8.2.10
 function MathLog(x) {
   if (!IS_NUMBER(x)) x = ToNumber(x);
-  return %Math_log(x);
+  return %_MathLog(x);
 }
 
 // ECMA 262 - 15.8.2.11

src/runtime.h

@@ -417,6 +417,7 @@ namespace internal {
   F(MathSin, 1, 1)                                                           \
   F(MathCos, 1, 1)                                                           \
   F(MathSqrt, 1, 1)                                                          \
+  F(MathLog, 1, 1)                                                           \
   F(IsRegExpEquivalent, 2, 1)                                                \
   F(HasCachedArrayIndex, 1, 1)                                               \
   F(GetCachedArrayIndex, 1, 1)                                               \

src/x64/assembler-x64.cc

@@ -2217,6 +2217,14 @@ void Assembler::fldpi() {
 }
 
 
+void Assembler::fldln2() {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  emit(0xD9);
+  emit(0xED);
+}
+
+
 void Assembler::fld_s(const Operand& adr) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;
@@ -2358,6 +2366,14 @@ void Assembler::fsin() {
 }
 
 
+void Assembler::fyl2x() {
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  emit(0xD9);
+  emit(0xF1);
+}
+
+
 void Assembler::fadd(int i) {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;

src/x64/assembler-x64.h

@@ -1046,6 +1046,7 @@ class Assembler : public Malloced {
   void fld1();
   void fldz();
   void fldpi();
+  void fldln2();
 
   void fld_s(const Operand& adr);
   void fld_d(const Operand& adr);
@@ -1100,6 +1101,7 @@ class Assembler : public Malloced {
 
   void fsin();
   void fcos();
+  void fyl2x();
 
   void frndint();
 

src/x64/code-stubs-x64.cc

@@ -1107,6 +1107,7 @@ Runtime::FunctionId TranscendentalCacheStub::RuntimeFunction() {
     // Add more cases when necessary.
     case TranscendentalCache::SIN: return Runtime::kMath_sin;
     case TranscendentalCache::COS: return Runtime::kMath_cos;
+    case TranscendentalCache::LOG: return Runtime::kMath_log;
     default:
       UNIMPLEMENTED();
       return Runtime::kAbort;
@@ -1121,73 +1122,76 @@ void TranscendentalCacheStub::GenerateOperation(MacroAssembler* masm,
   // rcx: Pointer to cache entry. Must be preserved.
   // st(0): Input double
   Label done;
-  ASSERT(type_ == TranscendentalCache::SIN ||
-         type_ == TranscendentalCache::COS);
-  // More transcendental types can be added later.
+  if (type_ == TranscendentalCache::SIN || type_ == TranscendentalCache::COS) {
+    // Both fsin and fcos require arguments in the range +/-2^63 and
+    // return NaN for infinities and NaN. They can share all code except
+    // the actual fsin/fcos operation.
+    Label in_range;
+    // If argument is outside the range -2^63..2^63, fsin/cos doesn't
+    // work. We must reduce it to the appropriate range.
+    __ movq(rdi, rbx);
+    // Move exponent and sign bits to low bits.
+    __ shr(rdi, Immediate(HeapNumber::kMantissaBits));
+    // Remove sign bit.
+    __ andl(rdi, Immediate((1 << HeapNumber::kExponentBits) - 1));
+    int supported_exponent_limit = (63 + HeapNumber::kExponentBias);
+    __ cmpl(rdi, Immediate(supported_exponent_limit));
+    __ j(below, &in_range);
+    // Check for infinity and NaN. Both return NaN for sin.
+    __ cmpl(rdi, Immediate(0x7ff));
+    __ j(equal, on_nan_result);
 
-  // Both fsin and fcos require arguments in the range +/-2^63 and
-  // return NaN for infinities and NaN. They can share all code except
-  // the actual fsin/fcos operation.
-  Label in_range;
-  // If argument is outside the range -2^63..2^63, fsin/cos doesn't
-  // work. We must reduce it to the appropriate range.
-  __ movq(rdi, rbx);
-  // Move exponent and sign bits to low bits.
-  __ shr(rdi, Immediate(HeapNumber::kMantissaBits));
-  // Remove sign bit.
-  __ andl(rdi, Immediate((1 << HeapNumber::kExponentBits) - 1));
-  int supported_exponent_limit = (63 + HeapNumber::kExponentBias);
-  __ cmpl(rdi, Immediate(supported_exponent_limit));
-  __ j(below, &in_range);
-  // Check for infinity and NaN. Both return NaN for sin.
-  __ cmpl(rdi, Immediate(0x7ff));
-  __ j(equal, on_nan_result);
+    // Use fpmod to restrict argument to the range +/-2*PI.
+    __ fldpi();
+    __ fadd(0);
+    __ fld(1);
+    // FPU Stack: input, 2*pi, input.
+    {
+      Label no_exceptions;
+      __ fwait();
+      __ fnstsw_ax();
+      // Clear if Illegal Operand or Zero Division exceptions are set.
+      __ testl(rax, Immediate(5));  // #IO and #ZD flags of FPU status word.
+      __ j(zero, &no_exceptions);
+      __ fnclex();
+      __ bind(&no_exceptions);
+    }
 
-  // Use fpmod to restrict argument to the range +/-2*PI.
-  __ fldpi();
-  __ fadd(0);
-  __ fld(1);
-  // FPU Stack: input, 2*pi, input.
-  {
-    Label no_exceptions;
-    __ fwait();
-    __ fnstsw_ax();
-    // Clear if Illegal Operand or Zero Division exceptions are set.
-    __ testl(rax, Immediate(5));  // #IO and #ZD flags of FPU status word.
-    __ j(zero, &no_exceptions);
-    __ fnclex();
-    __ bind(&no_exceptions);
+    // Compute st(0) % st(1)
+    {
+      NearLabel partial_remainder_loop;
+      __ bind(&partial_remainder_loop);
+      __ fprem1();
+      __ fwait();
+      __ fnstsw_ax();
+      __ testl(rax, Immediate(0x400));  // Check C2 bit of FPU status word.
+      // If C2 is set, computation only has partial result. Loop to
+      // continue computation.
+      __ j(not_zero, &partial_remainder_loop);
   }
-
-  // Compute st(0) % st(1)
-  {
-    NearLabel partial_remainder_loop;
-    __ bind(&partial_remainder_loop);
-    __ fprem1();
-    __ fwait();
-    __ fnstsw_ax();
-    __ testl(rax, Immediate(0x400));  // Check C2 bit of FPU status word.
-    // If C2 is set, computation only has partial result. Loop to
-    // continue computation.
-    __ j(not_zero, &partial_remainder_loop);
+    // FPU Stack: input, 2*pi, input % 2*pi
+    __ fstp(2);
+    // FPU Stack: input % 2*pi, 2*pi,
+    __ fstp(0);
+    // FPU Stack: input % 2*pi
+    __ bind(&in_range);
+    switch (type_) {
+      case TranscendentalCache::SIN:
+        __ fsin();
+        break;
+      case TranscendentalCache::COS:
+        __ fcos();
+        break;
+      default:
+        UNREACHABLE();
+    }
+    __ bind(&done);
+  } else {
+    ASSERT(type_ == TranscendentalCache::LOG);
+    __ fldln2();
+    __ fxch();
+    __ fyl2x();
   }
-  // FPU Stack: input, 2*pi, input % 2*pi
-  __ fstp(2);
-  // FPU Stack: input % 2*pi, 2*pi,
-  __ fstp(0);
-  // FPU Stack: input % 2*pi
-  __ bind(&in_range);
-  switch (type_) {
-    case TranscendentalCache::SIN:
-      __ fsin();
-      break;
-    case TranscendentalCache::COS:
-      __ fcos();
-      break;
-    default:
-      UNREACHABLE();
-  }
-  __ bind(&done);
 }
 
 

src/x64/codegen-x64.cc

@@ -7111,6 +7111,15 @@ void CodeGenerator::GenerateMathCos(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateMathLog(ZoneList<Expression*>* args) {
+  ASSERT_EQ(args->length(), 1);
+  Load(args->at(0));
+  TranscendentalCacheStub stub(TranscendentalCache::LOG);
+  Result result = frame_->CallStub(&stub, 1);
+  frame_->Push(&result);
+}
+
+
 // Generates the Math.sqrt method. Please note - this function assumes that
 // the callsite has executed ToNumber on the argument.
 void CodeGenerator::GenerateMathSqrt(ZoneList<Expression*>* args) {

src/x64/codegen-x64.h

@@ -664,14 +664,16 @@ class CodeGenerator: public AstVisitor {
   void GenerateMathSin(ZoneList<Expression*>* args);
   void GenerateMathCos(ZoneList<Expression*>* args);
   void GenerateMathSqrt(ZoneList<Expression*>* args);
+  void GenerateMathLog(ZoneList<Expression*>* args);
 
+  // Check whether two RegExps are equivalent.
   void GenerateIsRegExpEquivalent(ZoneList<Expression*>* args);
 
   void GenerateHasCachedArrayIndex(ZoneList<Expression*>* args);
   void GenerateGetCachedArrayIndex(ZoneList<Expression*>* args);
   void GenerateFastAsciiArrayJoin(ZoneList<Expression*>* args);
 
-// Simple condition analysis.
+  // Simple condition analysis.
   enum ConditionAnalysis {
     ALWAYS_TRUE,
     ALWAYS_FALSE,

src/x64/disasm-x64.cc

@@ -906,7 +906,9 @@ int DisassemblerX64::RegisterFPUInstruction(int escape_opcode,
             case 0xE4: mnem = "ftst"; break;
             case 0xE8: mnem = "fld1"; break;
             case 0xEB: mnem = "fldpi"; break;
+            case 0xED: mnem = "fldln2"; break;
             case 0xEE: mnem = "fldz"; break;
+            case 0xF1: mnem = "fyl2x"; break;
             case 0xF5: mnem = "fprem1"; break;
             case 0xF7: mnem = "fincstp"; break;
             case 0xF8: mnem = "fprem"; break;

src/x64/full-codegen-x64.cc

@@ -2623,6 +2623,16 @@ void FullCodeGenerator::EmitMathCos(ZoneList<Expression*>* args) {
 }
 
 
+void FullCodeGenerator::EmitMathLog(ZoneList<Expression*>* args) {
+  // Load the argument on the stack and call the stub.
+  TranscendentalCacheStub stub(TranscendentalCache::LOG);
+  ASSERT(args->length() == 1);
+  VisitForStackValue(args->at(0));
+  __ CallStub(&stub);
+  context()->Plug(rax);
+}
+
+
 void FullCodeGenerator::EmitMathSqrt(ZoneList<Expression*>* args) {
   // Load the argument on the stack and call the runtime function.
   ASSERT(args->length() == 1);