Custom call IC for Math.floor.

src/ia32/stub-cache-ia32.cc

Index: src/ia32/stub-cache-ia32.cc
diff --git a/src/ia32/stub-cache-ia32.cc b/src/ia32/stub-cache-ia32.cc
index 828e71a8fbbc839ac93c0d73ca4c4a9d235d864e..d40b51eee18c33e0209d0a7dd2071e4dd8f324dd 100644
--- a/src/ia32/stub-cache-ia32.cc
+++ b/src/ia32/stub-cache-ia32.cc
@@ -1813,6 +1813,131 @@ Object* CallStubCompiler::CompileStringFromCharCodeCall(
 }
 
 
+Object* CallStubCompiler::CompileMathFloorCall(Object* object,
+                                               JSObject* holder,
+                                               JSGlobalPropertyCell* cell,
+                                               JSFunction* function,
+                                               String* name) {
+  // ----------- S t a t e -------------
+  //  -- ecx                 : name
+  //  -- esp[0]              : return address
+  //  -- esp[(argc - n) * 4] : arg[n] (zero-based)
+  //  -- ...
+  //  -- esp[(argc + 1) * 4] : receiver
+  // -----------------------------------
+
+  if (!CpuFeatures::IsSupported(SSE2)) return Heap::undefined_value();
+  CpuFeatures::Scope use_sse2(SSE2);
+
+  const int argc = arguments().immediate();
+
+  // If the object is not a JSObject or we got an unexpected number of
+  // arguments, bail out to the regular call.
+  if (!object->IsJSObject() || argc != 1) return Heap::undefined_value();
+
+  Label miss;
+  GenerateNameCheck(name, &miss);
+
+  if (cell == NULL) {
+    __ mov(edx, Operand(esp, 2 * kPointerSize));
+
+    STATIC_ASSERT(kSmiTag == 0);
+    __ test(edx, Immediate(kSmiTagMask));
+    __ j(zero, &miss);
+
+    CheckPrototypes(JSObject::cast(object), edx, holder, ebx, eax, edi, name,
+                    &miss);
+  } else {
+    ASSERT(cell->value() == function);
+    GenerateGlobalReceiverCheck(JSObject::cast(object), holder, name, &miss);
+    GenerateLoadFunctionFromCell(cell, function, &miss);
+  }
+
+  // Load the (only) argument into eax.
+  __ mov(eax, Operand(esp, 1 * kPointerSize));
+
+  // Check if the argument is a smi.
+  Label smi;
+  STATIC_ASSERT(kSmiTag == 0);
+  __ test(eax, Immediate(kSmiTagMask));
+  __ j(zero, &smi);
+
+  // Check if the argument is a heap number and load its value into xmm0.
+  Label slow;
+  __ CheckMap(eax, Factory::heap_number_map(), &slow, true);
+  __ movdbl(xmm0, FieldOperand(eax, HeapNumber::kValueOffset));
+
+  // Check if the argument is strictly positive. Note this also
+  // discards NaN.

[Erik Corry, 2010/09/20 11:56:50]

It might be nice to detect +- zero and pass it through unchanged.  Zero is
probably reasonably common.  Once you have done that then negative numbers are
perhaps not so hard?  It seems like it's the same except you want to subtract
then add instead of adding then subtracting below and then you need to reverse
the rest too.  You can save this for another change or not do it at all :-)

[Vitaly Repeshko, 2010/09/21 12:54:49]

I filed a bug to consider extending it.

+  __ xorpd(xmm1, xmm1);
+  __ ucomisd(xmm0, xmm1);
+  __ j(below_equal, &slow);
+
+  // Do a truncating conversion.
+  __ cvttsd2si(eax, Operand(xmm0));
+
+  // Check if the result fits into a smi. Note this also checks for
+  // 0x80000000 which signals a failed conversion.
+  Label wont_fit_into_smi;
+  __ test(eax, Immediate(0xc0000000));
+  __ j(not_zero, &wont_fit_into_smi);
+
+  // Smi tag and return.
+  __ SmiTag(eax);
+  __ bind(&smi);
+  __ ret(2 * kPointerSize);
+
+  // Check if the argument is < 2^kMantissaBits.
+  Label already_round;
+  __ bind(&wont_fit_into_smi);
+  __ LoadPowerOf2(xmm1, ebx, HeapNumber::kMantissaBits);
+  __ ucomisd(xmm0, xmm1);
+  __ j(above_equal, &already_round);
+
+  // Save a copy of the argument.
+  __ movaps(xmm2, Operand(xmm0));
+
+  // Compute (argument + 2^kMantissaBits) - 2^kMantissaBits.
+  __ addsd(xmm0, xmm1);
+  __ subsd(xmm0, xmm1);
+
+  // Compare the argument and the tentative result to get the right mask:
+  //   if xmm2 < xmm0:
+  //     xmm2 = 1...1
+  //   else:
+  //     xmm2 = 0...0
+  __ cmpltsd(xmm2, xmm0);
+
+  // Subtract 1 if the argument was less than the tentative result.
+  __ LoadPowerOf2(xmm1, ebx, 0);
+  __ andpd(xmm1, Operand(xmm2));
+  __ subsd(xmm0, xmm1);
+
+  // Return a new heap number.
+  __ AllocateHeapNumber(eax, ebx, edx, &slow);
+  __ movdbl(FieldOperand(eax, HeapNumber::kValueOffset), xmm0);
+  __ ret(2 * kPointerSize);
+
+  // Return the argument (when it's an already round heap number).
+  __ bind(&already_round);
+  __ mov(eax, Operand(esp, 1 * kPointerSize));
+  __ ret(2 * kPointerSize);
+
+  // Tail call the full function. We do not have to patch the receiver
+  // because the function makes no use of it.
+  __ bind(&slow);
+  __ InvokeFunction(function, arguments(), JUMP_FUNCTION);
+
+  __ bind(&miss);
+  // ecx: function name.
+  Object* obj = GenerateMissBranch();
+  if (obj->IsFailure()) return obj;
+
+  // Return the generated code.
+  return (cell == NULL) ? GetCode(function) : GetCode(NORMAL, name);
+}
+
+
 Object* CallStubCompiler::CompileCallConstant(Object* object,
                                               JSObject* holder,
                                               JSFunction* function,