Truncate rather than round to nearest when performing float-to-integer...

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
===================================================================
--- src/x64/stub-cache-x64.cc	(revision 6406)
+++ src/x64/stub-cache-x64.cc	(working copy)
@@ -3144,6 +3144,306 @@
 }
 
 
+MaybeObject* ExternalArrayStubCompiler::CompileKeyedLoadStub(
+    ExternalArrayType array_type, Code::Flags flags) {
+  // ----------- S t a t e -------------
+  //  -- rax    : key
+  //  -- rdx    : receiver
+  //  -- rsp[0] : return address
+  // -----------------------------------
+  Label slow;
+
+  // Check that the object isn't a smi.
+  __ JumpIfSmi(rdx, &slow);
+
+  // Check that the key is a smi.
+  __ JumpIfNotSmi(rax, &slow);
+
+  // Check that the object is a JS object.
+  __ CmpObjectType(rdx, JS_OBJECT_TYPE, rcx);
+  __ j(not_equal, &slow);
+  // Check that the receiver does not require access checks.  We need
+  // to check this explicitly since this generic stub does not perform
+  // map checks.  The map is already in rdx.
+  __ testb(FieldOperand(rcx, Map::kBitFieldOffset),
+           Immediate(1 << Map::kIsAccessCheckNeeded));
+  __ j(not_zero, &slow);
+
+  // Check that the elements array is the appropriate type of
+  // ExternalArray.
+  // rax: index (as a smi)
+  // rdx: JSObject
+  __ movq(rbx, FieldOperand(rdx, JSObject::kElementsOffset));
+  __ CompareRoot(FieldOperand(rbx, HeapObject::kMapOffset),
+                 Heap::RootIndexForExternalArrayType(array_type));
+  __ j(not_equal, &slow);
+
+  // Check that the index is in range.
+  __ SmiToInteger32(rcx, rax);
+  __ cmpl(rcx, FieldOperand(rbx, ExternalArray::kLengthOffset));
+  // Unsigned comparison catches both negative and too-large values.
+  __ j(above_equal, &slow);
+
+  // rax: index (as a smi)
+  // rdx: receiver (JSObject)
+  // rcx: untagged index
+  // rbx: elements array
+  __ movq(rbx, FieldOperand(rbx, ExternalArray::kExternalPointerOffset));
+  // rbx: base pointer of external storage
+  switch (array_type) {
+    case kExternalByteArray:
+      __ movsxbq(rcx, Operand(rbx, rcx, times_1, 0));
+      break;
+    case kExternalUnsignedByteArray:
+      __ movzxbq(rcx, Operand(rbx, rcx, times_1, 0));
+      break;
+    case kExternalShortArray:
+      __ movsxwq(rcx, Operand(rbx, rcx, times_2, 0));
+      break;
+    case kExternalUnsignedShortArray:
+      __ movzxwq(rcx, Operand(rbx, rcx, times_2, 0));
+      break;
+    case kExternalIntArray:
+      __ movsxlq(rcx, Operand(rbx, rcx, times_4, 0));
+      break;
+    case kExternalUnsignedIntArray:
+      __ movl(rcx, Operand(rbx, rcx, times_4, 0));
+      break;
+    case kExternalFloatArray:
+      __ cvtss2sd(xmm0, Operand(rbx, rcx, times_4, 0));
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+
+  // rax: index
+  // rdx: receiver
+  // For integer array types:
+  // rcx: value
+  // For floating-point array type:
+  // xmm0: value as double.
+
+  ASSERT(kSmiValueSize == 32);
+  if (array_type == kExternalUnsignedIntArray) {
+    // For the UnsignedInt array type, we need to see whether
+    // the value can be represented in a Smi. If not, we need to convert
+    // it to a HeapNumber.
+    NearLabel box_int;
+
+    __ JumpIfUIntNotValidSmiValue(rcx, &box_int);
+
+    __ Integer32ToSmi(rax, rcx);
+    __ ret(0);
+
+    __ bind(&box_int);
+
+    // Allocate a HeapNumber for the int and perform int-to-double
+    // conversion.
+    // The value is zero-extended since we loaded the value from memory
+    // with movl.
+    __ cvtqsi2sd(xmm0, rcx);
+
+    __ AllocateHeapNumber(rcx, rbx, &slow);
+    // Set the value.
+    __ movsd(FieldOperand(rcx, HeapNumber::kValueOffset), xmm0);
+    __ movq(rax, rcx);
+    __ ret(0);
+  } else if (array_type == kExternalFloatArray) {
+    // For the floating-point array type, we need to always allocate a
+    // HeapNumber.
+    __ AllocateHeapNumber(rcx, rbx, &slow);
+    // Set the value.
+    __ movsd(FieldOperand(rcx, HeapNumber::kValueOffset), xmm0);
+    __ movq(rax, rcx);
+    __ ret(0);
+  } else {
+    __ Integer32ToSmi(rax, rcx);
+    __ ret(0);
+  }
+
+  // Slow case: Jump to runtime.
+  __ bind(&slow);
+  __ IncrementCounter(&Counters::keyed_load_external_array_slow, 1);
+
+  // ----------- S t a t e -------------
+  //  -- rax    : key
+  //  -- rdx    : receiver
+  //  -- rsp[0]  : return address
+  // -----------------------------------
+
+  __ pop(rbx);
+  __ push(rdx);  // receiver
+  __ push(rax);  // name
+  __ push(rbx);  // return address
+
+  // Perform tail call to the entry.
+  __ TailCallRuntime(Runtime::kKeyedGetProperty, 2, 1);
+
+  // Return the generated code.
+  return GetCode(flags);
+}
+
+
+MaybeObject* ExternalArrayStubCompiler::CompileKeyedStoreStub(
+    ExternalArrayType array_type, Code::Flags flags) {
+  // ----------- S t a t e -------------
+  //  -- rax     : value
+  //  -- rcx     : key
+  //  -- rdx     : receiver
+  //  -- rsp[0]  : return address
+  // -----------------------------------
+  Label slow;
+
+  // Check that the object isn't a smi.
+  __ JumpIfSmi(rdx, &slow);
+  // Get the map from the receiver.
+  __ movq(rbx, FieldOperand(rdx, HeapObject::kMapOffset));
+  // Check that the receiver does not require access checks.  We need
+  // to do this because this generic stub does not perform map checks.
+  __ testb(FieldOperand(rbx, Map::kBitFieldOffset),
+           Immediate(1 << Map::kIsAccessCheckNeeded));
+  __ j(not_zero, &slow);
+  // Check that the key is a smi.
+  __ JumpIfNotSmi(rcx, &slow);
+
+  // Check that the object is a JS object.
+  __ CmpInstanceType(rbx, JS_OBJECT_TYPE);
+  __ j(not_equal, &slow);
+
+  // Check that the elements array is the appropriate type of
+  // ExternalArray.
+  // rax: value
+  // rcx: key (a smi)
+  // rdx: receiver (a JSObject)
+  __ movq(rbx, FieldOperand(rdx, JSObject::kElementsOffset));
+  __ CompareRoot(FieldOperand(rbx, HeapObject::kMapOffset),
+                 Heap::RootIndexForExternalArrayType(array_type));
+  __ j(not_equal, &slow);
+
+  // Check that the index is in range.
+  __ SmiToInteger32(rdi, rcx);  // Untag the index.
+  __ cmpl(rdi, FieldOperand(rbx, ExternalArray::kLengthOffset));
+  // Unsigned comparison catches both negative and too-large values.
+  __ j(above_equal, &slow);
+
+  // Handle both smis and HeapNumbers in the fast path. Go to the
+  // runtime for all other kinds of values.
+  // rax: value
+  // rcx: key (a smi)
+  // rdx: receiver (a JSObject)
+  // rbx: elements array
+  // rdi: untagged key
+  NearLabel check_heap_number;
+  __ JumpIfNotSmi(rax, &check_heap_number);
+  // No more branches to slow case on this path.  Key and receiver not needed.
+  __ SmiToInteger32(rdx, rax);
+  __ movq(rbx, FieldOperand(rbx, ExternalArray::kExternalPointerOffset));
+  // rbx: base pointer of external storage
+  switch (array_type) {
+    case kExternalByteArray:
+    case kExternalUnsignedByteArray:
+      __ movb(Operand(rbx, rdi, times_1, 0), rdx);
+      break;
+    case kExternalShortArray:
+    case kExternalUnsignedShortArray:
+      __ movw(Operand(rbx, rdi, times_2, 0), rdx);
+      break;
+    case kExternalIntArray:
+    case kExternalUnsignedIntArray:
+      __ movl(Operand(rbx, rdi, times_4, 0), rdx);
+      break;
+    case kExternalFloatArray:
+      // Need to perform int-to-float conversion.
+      __ cvtlsi2ss(xmm0, rdx);
+      __ movss(Operand(rbx, rdi, times_4, 0), xmm0);
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+  __ ret(0);
+
+  __ bind(&check_heap_number);
+  // rax: value
+  // rcx: key (a smi)
+  // rdx: receiver (a JSObject)
+  // rbx: elements array
+  // rdi: untagged key
+  __ CmpObjectType(rax, HEAP_NUMBER_TYPE, kScratchRegister);
+  __ j(not_equal, &slow);
+  // No more branches to slow case on this path.
+
+  // The WebGL specification leaves the behavior of storing NaN and
+  // +/-Infinity into integer arrays basically undefined. For more
+  // reproducible behavior, convert these to zero.
+  __ movsd(xmm0, FieldOperand(rax, HeapNumber::kValueOffset));
+  __ movq(rbx, FieldOperand(rbx, ExternalArray::kExternalPointerOffset));
+  // rdi: untagged index
+  // rbx: base pointer of external storage
+  // top of FPU stack: value
+  if (array_type == kExternalFloatArray) {
+    __ cvtsd2ss(xmm0, xmm0);
+    __ movss(Operand(rbx, rdi, times_4, 0), xmm0);
+    __ ret(0);
+  } else {
+    // Perform float-to-int conversion with truncation (round-to-zero)
+    // behavior.
+
+    // Convert to int32 and store the low byte/word.
+    // If the value is NaN or +/-infinity, the result is 0x80000000,
+    // which is automatically zero when taken mod 2^n, n < 32.
+    // rdx: value (converted to an untagged integer)
+    // rdi: untagged index
+    // rbx: base pointer of external storage
+    switch (array_type) {
+      case kExternalByteArray:
+      case kExternalUnsignedByteArray:
+        __ cvttsd2si(rdx, xmm0);
+        __ movb(Operand(rbx, rdi, times_1, 0), rdx);
+        break;
+      case kExternalShortArray:
+      case kExternalUnsignedShortArray:
+        __ cvttsd2si(rdx, xmm0);
+        __ movw(Operand(rbx, rdi, times_2, 0), rdx);
+        break;
+      case kExternalIntArray:
+      case kExternalUnsignedIntArray: {
+        // Convert to int64, so that NaN and infinities become
+        // 0x8000000000000000, which is zero mod 2^32.
+        __ cvttsd2siq(rdx, xmm0);
+        __ movl(Operand(rbx, rdi, times_4, 0), rdx);
+        break;
+      }
+      default:
+        UNREACHABLE();
+        break;
+    }
+    __ ret(0);
+  }
+
+  // Slow case: call runtime.
+  __ bind(&slow);
+
+  // ----------- S t a t e -------------
+  //  -- rax     : value
+  //  -- rcx     : key
+  //  -- rdx     : receiver
+  //  -- rsp[0]  : return address
+  // -----------------------------------
+
+  __ pop(rbx);
+  __ push(rdx);  // receiver
+  __ push(rcx);  // key
+  __ push(rax);  // value
+  __ push(rbx);  // return address
+
+  // Do tail-call to runtime routine.
+  __ TailCallRuntime(Runtime::kSetProperty, 3, 1);
+
+  return GetCode(flags);
+}
+
 #undef __
 
 } }  // namespace v8::internal