Revert of [builtins] Introduce proper Float64Exp operator.

src/mips/codegen-mips.cc

Index: src/mips/codegen-mips.cc
diff --git a/src/mips/codegen-mips.cc b/src/mips/codegen-mips.cc
index 07cab806995b760def12b462717188fc0a7cbf93..63bbda3168b3dd826e75f99a4621788627384ba9 100644
--- a/src/mips/codegen-mips.cc
+++ b/src/mips/codegen-mips.cc
@@ -15,6 +15,60 @@
 
 
 #define __ masm.
+
+
+#if defined(USE_SIMULATOR)
+byte* fast_exp_mips_machine_code = nullptr;
+double fast_exp_simulator(double x, Isolate* isolate) {
+  return Simulator::current(isolate)->CallFP(fast_exp_mips_machine_code, x, 0);
+}
+#endif
+
+
+UnaryMathFunctionWithIsolate CreateExpFunction(Isolate* isolate) {
+  size_t actual_size;
+  byte* buffer =
+      static_cast<byte*>(base::OS::Allocate(1 * KB, &actual_size, true));
+  if (buffer == nullptr) return nullptr;
+  ExternalReference::InitializeMathExpData();
+
+  MacroAssembler masm(isolate, buffer, static_cast<int>(actual_size),
+                      CodeObjectRequired::kNo);
+
+  {
+    DoubleRegister input = f12;
+    DoubleRegister result = f0;
+    DoubleRegister double_scratch1 = f4;
+    DoubleRegister double_scratch2 = f6;
+    Register temp1 = t0;
+    Register temp2 = t1;
+    Register temp3 = t2;
+
+    __ MovFromFloatParameter(input);
+    __ Push(temp3, temp2, temp1);
+    MathExpGenerator::EmitMathExp(
+        &masm, input, result, double_scratch1, double_scratch2,
+        temp1, temp2, temp3);
+    __ Pop(temp3, temp2, temp1);
+    __ MovToFloatResult(result);
+    __ Ret();
+  }
+
+  CodeDesc desc;
+  masm.GetCode(&desc);
+  DCHECK(!RelocInfo::RequiresRelocation(desc));
+
+  Assembler::FlushICache(isolate, buffer, actual_size);
+  base::OS::ProtectCode(buffer, actual_size);
+
+#if !defined(USE_SIMULATOR)
+  return FUNCTION_CAST<UnaryMathFunctionWithIsolate>(buffer);
+#else
+  fast_exp_mips_machine_code = buffer;
+  return &fast_exp_simulator;
+#endif
+}
+
 
 #if defined(V8_HOST_ARCH_MIPS)
 MemCopyUint8Function CreateMemCopyUint8Function(Isolate* isolate,
@@ -1038,6 +1092,95 @@
   __ bind(&done);
 }
 
+
+static MemOperand ExpConstant(int index, Register base) {
+  return MemOperand(base, index * kDoubleSize);
+}
+
+
+void MathExpGenerator::EmitMathExp(MacroAssembler* masm,
+                                   DoubleRegister input,
+                                   DoubleRegister result,
+                                   DoubleRegister double_scratch1,
+                                   DoubleRegister double_scratch2,
+                                   Register temp1,
+                                   Register temp2,
+                                   Register temp3) {
+  DCHECK(!input.is(result));
+  DCHECK(!input.is(double_scratch1));
+  DCHECK(!input.is(double_scratch2));
+  DCHECK(!result.is(double_scratch1));
+  DCHECK(!result.is(double_scratch2));
+  DCHECK(!double_scratch1.is(double_scratch2));
+  DCHECK(!temp1.is(temp2));
+  DCHECK(!temp1.is(temp3));
+  DCHECK(!temp2.is(temp3));
+  DCHECK(ExternalReference::math_exp_constants(0).address() != NULL);
+  DCHECK(!masm->serializer_enabled());  // External references not serializable.
+
+  Label zero, infinity, done;
+
+  __ li(temp3, Operand(ExternalReference::math_exp_constants(0)));
+
+  __ ldc1(double_scratch1, ExpConstant(0, temp3));
+  __ BranchF(&zero, NULL, ge, double_scratch1, input);
+
+  __ ldc1(double_scratch2, ExpConstant(1, temp3));
+  __ BranchF(&infinity, NULL, ge, input, double_scratch2);
+
+  __ ldc1(double_scratch1, ExpConstant(3, temp3));
+  __ ldc1(result, ExpConstant(4, temp3));
+  __ mul_d(double_scratch1, double_scratch1, input);
+  __ add_d(double_scratch1, double_scratch1, result);
+  __ FmoveLow(temp2, double_scratch1);
+  __ sub_d(double_scratch1, double_scratch1, result);
+  __ ldc1(result, ExpConstant(6, temp3));
+  __ ldc1(double_scratch2, ExpConstant(5, temp3));
+  __ mul_d(double_scratch1, double_scratch1, double_scratch2);
+  __ sub_d(double_scratch1, double_scratch1, input);
+  __ sub_d(result, result, double_scratch1);
+  __ mul_d(double_scratch2, double_scratch1, double_scratch1);
+  __ mul_d(result, result, double_scratch2);
+  __ ldc1(double_scratch2, ExpConstant(7, temp3));
+  __ mul_d(result, result, double_scratch2);
+  __ sub_d(result, result, double_scratch1);
+  // Mov 1 in double_scratch2 as math_exp_constants_array[8] == 1.
+  DCHECK(*reinterpret_cast<double*>
+         (ExternalReference::math_exp_constants(8).address()) == 1);
+  __ Move(double_scratch2, 1.);
+  __ add_d(result, result, double_scratch2);
+  __ srl(temp1, temp2, 11);
+  __ Ext(temp2, temp2, 0, 11);
+  __ Addu(temp1, temp1, Operand(0x3ff));
+
+  // Must not call ExpConstant() after overwriting temp3!
+  __ li(temp3, Operand(ExternalReference::math_exp_log_table()));
+  __ Lsa(temp3, temp3, temp2, 3);
+  __ lw(temp2, MemOperand(temp3, Register::kMantissaOffset));
+  __ lw(temp3, MemOperand(temp3, Register::kExponentOffset));
+  // The first word is loaded is the lower number register.
+  if (temp2.code() < temp3.code()) {
+    __ sll(at, temp1, 20);
+    __ Or(temp1, temp3, at);
+    __ Move(double_scratch1, temp2, temp1);
+  } else {
+    __ sll(at, temp1, 20);
+    __ Or(temp1, temp2, at);
+    __ Move(double_scratch1, temp3, temp1);
+  }
+  __ mul_d(result, result, double_scratch1);
+  __ BranchShort(&done);
+
+  __ bind(&zero);
+  __ Move(result, kDoubleRegZero);
+  __ BranchShort(&done);
+
+  __ bind(&infinity);
+  __ ldc1(result, ExpConstant(2, temp3));
+
+  __ bind(&done);
+}
+
 #ifdef DEBUG
 // nop(CODE_AGE_MARKER_NOP)
 static const uint32_t kCodeAgePatchFirstInstruction = 0x00010180;