Optimize bitops with non-Smi inputs. Instead of converting both inputs

to floating point and then converting back we convert directly to a
32 bit integer.  In addition the bit twiddling implementation of float-
to-integer conversion has been ported from ARM.  Testing has shown that
this runs faster than the x87 or SSE3 rounding instructions.  This change
is IA32 only.  There may be a smaller benefit from doing the same on x64.
Review URL: http://codereview.chromium.org/506052

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3492 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/codegen.h

@@ -305,7 +305,9 @@ class UnarySubStub : public CodeStub {
   int MinorKey() { return overwrite_ ? 1 : 0; }
   void Generate(MacroAssembler* masm);
 
-  const char* GetName() { return "UnarySubStub"; }
+  const char* GetName() {
+    return overwrite_ ? "UnarySubStub_Overwrite" : "UnarySubStub_Alloc";
+  }
 };
 
 

src/ia32/codegen-ia32.cc

@@ -761,6 +761,10 @@ class FloatingPointHelper : public AllStatic {
   static void CheckFloatOperands(MacroAssembler* masm,
                                  Label* non_float,
                                  Register scratch);
+  // Takes the operands in edx and eax and loads them as integers in eax
+  // and ecx.
+  static void LoadAsIntegers(MacroAssembler* masm,
+                             Label* operand_conversion_failure);
   // Test if operands are numbers (smi or HeapNumber objects), and load
   // them into xmm0 and xmm1 if they are.  Jump to label not_numbers if
   // either operand is not a number.  Operands are in edx and eax.
@@ -771,8 +775,8 @@ class FloatingPointHelper : public AllStatic {
 
 const char* GenericBinaryOpStub::GetName() {
   if (name_ != NULL) return name_;
-  const int len = 100;
-  name_ = Bootstrapper::AllocateAutoDeletedArray(len);
+  const int kMaxNameLength = 100;
+  name_ = Bootstrapper::AllocateAutoDeletedArray(kMaxNameLength);
   if (name_ == NULL) return "OOM";
   const char* op_name = Token::Name(op_);
   const char* overwrite_name;
@@ -783,7 +787,7 @@ const char* GenericBinaryOpStub::GetName() {
     default: overwrite_name = "UnknownOverwrite"; break;
   }
 
-  OS::SNPrintF(Vector<char>(name_, len),
+  OS::SNPrintF(Vector<char>(name_, kMaxNameLength),
                "GenericBinaryOpStub_%s_%s%s_%s%s",
                op_name,
                overwrite_name,
@@ -7234,42 +7238,11 @@ void GenericBinaryOpStub::Generate(MacroAssembler* masm) {
     case Token::SAR:
     case Token::SHL:
     case Token::SHR: {
-      FloatingPointHelper::CheckFloatOperands(masm, &call_runtime, ebx);
-      FloatingPointHelper::LoadFloatOperands(masm, ecx);
-
-      Label skip_allocation, non_smi_result, operand_conversion_failure;
-
-      // Reserve space for converted numbers.
-      __ sub(Operand(esp), Immediate(2 * kPointerSize));
-
-      if (use_sse3_) {
-        // Truncate the operands to 32-bit integers and check for
-        // exceptions in doing so.
-        CpuFeatures::Scope scope(SSE3);
-        __ fisttp_s(Operand(esp, 0 * kPointerSize));
-        __ fisttp_s(Operand(esp, 1 * kPointerSize));
-        __ fnstsw_ax();
-        __ test(eax, Immediate(1));
-        __ j(not_zero, &operand_conversion_failure);
-      } else {
-        // Check if right operand is int32.
-        __ fist_s(Operand(esp, 0 * kPointerSize));
-        __ fild_s(Operand(esp, 0 * kPointerSize));
-        __ FCmp();
-        __ j(not_zero, &operand_conversion_failure);
-        __ j(parity_even, &operand_conversion_failure);
-
-        // Check if left operand is int32.
-        __ fist_s(Operand(esp, 1 * kPointerSize));
-        __ fild_s(Operand(esp, 1 * kPointerSize));
-        __ FCmp();
-        __ j(not_zero, &operand_conversion_failure);
-        __ j(parity_even, &operand_conversion_failure);
-      }
-
-      // Get int32 operands and perform bitop.
-      __ pop(ecx);
-      __ pop(eax);
+      Label non_smi_result, skip_allocation;
+      Label operand_conversion_failure;
+      FloatingPointHelper::LoadAsIntegers(
+        masm,
+        &operand_conversion_failure);
       switch (op_) {
         case Token::BIT_OR:  __ or_(eax, Operand(ecx)); break;
         case Token::BIT_AND: __ and_(eax, Operand(ecx)); break;
@@ -7321,22 +7294,8 @@ void GenericBinaryOpStub::Generate(MacroAssembler* masm) {
         GenerateReturn(masm);
       }
 
-      // Clear the FPU exception flag and reset the stack before calling
-      // the runtime system.
+      // Go to runtime for non-number inputs.
       __ bind(&operand_conversion_failure);
-      __ add(Operand(esp), Immediate(2 * kPointerSize));
-      if (use_sse3_) {
-        // If we've used the SSE3 instructions for truncating the
-        // floating point values to integers and it failed, we have a
-        // pending #IA exception. Clear it.
-        __ fnclex();
-      } else {
-        // The non-SSE3 variant does early bailout if the right
-        // operand isn't a 32-bit integer, so we may have a single
-        // value on the FPU stack we need to get rid of.
-        __ ffree(0);
-      }
-
       // SHR should return uint32 - go to runtime for non-smi/negative result.
       if (op_ == Token::SHR) {
         __ bind(&non_smi_result);
@@ -7460,6 +7419,162 @@ void GenericBinaryOpStub::GenerateReturn(MacroAssembler* masm) {
 }
 
 
+// Get the integer part of a heap number.  Surprisingly, all this bit twiddling
+// is faster than using the built-in instructions on floating point registers.
+// Trashes edi and ebx.  Dest is ecx.  Source cannot be ecx or one of the
+// trashed registers.
+void IntegerConvert(MacroAssembler* masm,
+                    Register source,
+                    Label* conversion_failure) {
+  Label done, right_exponent, normal_exponent;
+  Register scratch = ebx;
+  Register scratch2 = edi;
+  // Get exponent word.
+  __ mov(scratch, FieldOperand(source, HeapNumber::kExponentOffset));
+  // Get exponent alone in scratch2.
+  __ mov(scratch2, scratch);
+  __ and_(scratch2, HeapNumber::kExponentMask);
+  // Load ecx with zero.  We use this either for the final shift or
+  // for the answer.
+  __ xor_(ecx, Operand(ecx));
+  // Check whether the exponent matches a 32 bit signed int that cannot be
+  // represented by a Smi.  A non-smi 32 bit integer is 1.xxx * 2^30 so the
+  // exponent is 30 (biased).  This is the exponent that we are fastest at and
+  // also the highest exponent we can handle here.
+  const uint32_t non_smi_exponent =
+      (HeapNumber::kExponentBias + 30) << HeapNumber::kExponentShift;
+  __ cmp(Operand(scratch2), Immediate(non_smi_exponent));
+  // If we have a match of the int32-but-not-Smi exponent then skip some logic.
+  __ j(equal, &right_exponent);
+  // If the exponent is higher than that then go to slow case.  This catches
+  // numbers that don't fit in a signed int32, infinities and NaNs.
+  __ j(less, &normal_exponent);
+
+  {
+    // Handle a big exponent.  The only reason we have this code is that the >>>
+    // operator has a tendency to generate numbers with an exponent of 31.
+    const uint32_t big_non_smi_exponent =
+        (HeapNumber::kExponentBias + 31) << HeapNumber::kExponentShift;
+    __ cmp(Operand(scratch2), Immediate(big_non_smi_exponent));
+    __ j(not_equal, conversion_failure);
+    // We have the big exponent, typically from >>>.  This means the number is
+    // in the range 2^31 to 2^32 - 1.  Get the top bits of the mantissa.
+    __ mov(scratch2, scratch);
+    __ and_(scratch2, HeapNumber::kMantissaMask);
+    // Put back the implicit 1.
+    __ or_(scratch2, 1 << HeapNumber::kExponentShift);
+    // Shift up the mantissa bits to take up the space the exponent used to
+    // take. We just orred in the implicit bit so that took care of one and
+    // we want to use the full unsigned range so we subtract 1 bit from the
+    // shift distance.
+    const int big_shift_distance = HeapNumber::kNonMantissaBitsInTopWord - 1;
+    __ shl(scratch2, big_shift_distance);
+    // Get the second half of the double.
+    __ mov(ecx, FieldOperand(source, HeapNumber::kMantissaOffset));
+    // Shift down 21 bits to get the most significant 11 bits or the low
+    // mantissa word.
+    __ shr(ecx, 32 - big_shift_distance);
+    __ or_(ecx, Operand(scratch2));
+    // We have the answer in ecx, but we may need to negate it.
+    __ test(scratch, Operand(scratch));
+    __ j(positive, &done);
+    __ neg(ecx);
+    __ jmp(&done);
+  }
+
+  __ bind(&normal_exponent);
+  // Exponent word in scratch, exponent part of exponent word in scratch2.
+  // Zero in ecx.
+  // We know the exponent is smaller than 30 (biased).  If it is less than
+  // 0 (biased) then the number is smaller in magnitude than 1.0 * 2^0, ie
+  // it rounds to zero.
+  const uint32_t zero_exponent =
+      (HeapNumber::kExponentBias + 0) << HeapNumber::kExponentShift;
+  __ sub(Operand(scratch2), Immediate(zero_exponent));
+  // ecx already has a Smi zero.
+  __ j(less, &done);
+
+  // We have a shifted exponent between 0 and 30 in scratch2.
+  __ shr(scratch2, HeapNumber::kExponentShift);
+  __ mov(ecx, Immediate(30));
+  __ sub(ecx, Operand(scratch2));
+
+  __ bind(&right_exponent);
+  // Here ecx is the shift, scratch is the exponent word.
+  // Get the top bits of the mantissa.
+  __ and_(scratch, HeapNumber::kMantissaMask);
+  // Put back the implicit 1.
+  __ or_(scratch, 1 << HeapNumber::kExponentShift);
+  // Shift up the mantissa bits to take up the space the exponent used to
+  // take. We have kExponentShift + 1 significant bits int he low end of the
+  // word.  Shift them to the top bits.
+  const int shift_distance = HeapNumber::kNonMantissaBitsInTopWord - 2;
+  __ shl(scratch, shift_distance);
+  // Get the second half of the double. For some exponents we don't
+  // actually need this because the bits get shifted out again, but
+  // it's probably slower to test than just to do it.
+  __ mov(scratch2, FieldOperand(source, HeapNumber::kMantissaOffset));
+  // Shift down 22 bits to get the most significant 10 bits or the low mantissa
+  // word.
+  __ shr(scratch2, 32 - shift_distance);
+  __ or_(scratch2, Operand(scratch));
+  // Move down according to the exponent.
+  __ shr_cl(scratch2);
+  // Now the unsigned answer is in scratch2.  We need to move it to ecx and
+  // we may need to fix the sign.
+  Label negative;
+  __ xor_(ecx, Operand(ecx));
+  __ cmp(ecx, FieldOperand(source, HeapNumber::kExponentOffset));
+  __ j(greater, &negative);
+  __ mov(ecx, scratch2);
+  __ jmp(&done);
+  __ bind(&negative);
+  __ sub(ecx, Operand(scratch2));
+  __ bind(&done);
+}
+
+
+// Input: edx, eax are the left and right objects of a bit op.
+// Output: eax, ecx are left and right integers for a bit op.
+void FloatingPointHelper::LoadAsIntegers(MacroAssembler* masm,
+                                         Label* conversion_failure) {
+  // Check float operands.
+  Label arg1_is_object, arg2_is_object, load_arg2;
+  Label done;
+
+  __ test(edx, Immediate(kSmiTagMask));
+  __ j(not_zero, &arg1_is_object);
+  __ sar(edx, kSmiTagSize);
+  __ jmp(&load_arg2);
+
+  __ bind(&arg1_is_object);
+  __ mov(ebx, FieldOperand(edx, HeapObject::kMapOffset));
+  __ cmp(ebx, Factory::heap_number_map());
+  __ j(not_equal, conversion_failure);
+  // Get the untagged integer version of the edx heap number in ecx.
+  IntegerConvert(masm, edx, conversion_failure);
+  __ mov(edx, ecx);
+
+  // Here edx has the untagged integer, eax has a Smi or a heap number.
+  __ bind(&load_arg2);
+  // Test if arg2 is a Smi.
+  __ test(eax, Immediate(kSmiTagMask));
+  __ j(not_zero, &arg2_is_object);
+  __ sar(eax, kSmiTagSize);
+  __ mov(ecx, eax);
+  __ jmp(&done);
+
+  __ bind(&arg2_is_object);
+  __ mov(ebx, FieldOperand(eax, HeapObject::kMapOffset));
+  __ cmp(ebx, Factory::heap_number_map());
+  __ j(not_equal, conversion_failure);
+  // Get the untagged integer version of the eax heap number in ecx.
+  IntegerConvert(masm, eax, conversion_failure);
+  __ bind(&done);
+  __ mov(eax, edx);
+}
+
+
 void FloatingPointHelper::LoadFloatOperand(MacroAssembler* masm,
                                            Register number) {
   Label load_smi, done;