[Atomics] code stubs for atomic operations

src/arm/code-stubs-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 5534 matching lines @@
   ExternalReference thunk_ref =
       ExternalReference::invoke_accessor_getter_callback(isolate());
 
   // +3 is to skip prolog, return address and name handle.
   MemOperand return_value_operand(
       fp, (PropertyCallbackArguments::kReturnValueOffset + 3) * kPointerSize);
   CallApiFunctionAndReturn(masm, api_function_address, thunk_ref,
                            kStackUnwindSpace, NULL, return_value_operand, NULL);
 }
 
+namespace {
+
+void GetTypedArrayBackingStore(MacroAssembler* masm, Register backing_store,
+                               Register object, Register scratch,
+                               LowDwVfpRegister double_scratch) {
+  Label offset_is_not_smi, done;
+  __ ldr(scratch, FieldMemOperand(object, JSTypedArray::kBufferOffset));
+  __ ldr(backing_store,
+         FieldMemOperand(scratch, JSArrayBuffer::kBackingStoreOffset));
+  __ ldr(scratch,
+         FieldMemOperand(object, JSArrayBufferView::kByteOffsetOffset));
+  __ UntagAndJumpIfNotSmi(scratch, scratch, &offset_is_not_smi);
+  // offset is smi
+  __ add(backing_store, backing_store, scratch);
+  __ jmp(&done);
+
+  // offset is a heap number
+  __ bind(&offset_is_not_smi);
+  __ vldr(double_scratch, scratch, HeapNumber::kValueOffset - kHeapObjectTag);

[Rodolph Perfetta, 2016/04/07 14:13:50]

When you arrive here, scratch has been untagged (UntagAndJumpIfNotSmi line 5566)
so it is not a valid pointer any more.

[binji, 2016/04/08 18:21:42]

Done.

+  __ vcvt_u32_f64(double_scratch.low(), double_scratch);
+  __ vmov(scratch, double_scratch.low());
+  __ add(backing_store, backing_store, scratch);
+  __ bind(&done);
+}
+
+void TypedArrayJumpTable(MacroAssembler* masm, Register object,
+                         Register scratch, Register scratch2, Label* i8,
+                         Label* u8, Label* i16, Label* u16, Label* i32,
+                         Label* u32, Label* u8c) {
+  STATIC_ASSERT(FIXED_UINT8_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 1);
+  STATIC_ASSERT(FIXED_INT16_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 2);
+  STATIC_ASSERT(FIXED_UINT16_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 3);
+  STATIC_ASSERT(FIXED_INT32_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 4);
+  STATIC_ASSERT(FIXED_UINT32_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 5);
+  STATIC_ASSERT(FIXED_FLOAT32_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 6);
+  STATIC_ASSERT(FIXED_FLOAT64_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 7);
+  STATIC_ASSERT(FIXED_UINT8_CLAMPED_ARRAY_TYPE == FIXED_INT8_ARRAY_TYPE + 8);
+
+  __ ldr(scratch, FieldMemOperand(object, JSObject::kElementsOffset));
+  __ ldr(scratch, FieldMemOperand(scratch, HeapObject::kMapOffset));
+  __ ldrb(scratch, FieldMemOperand(scratch, Map::kInstanceTypeOffset));
+  __ mov(scratch2, Operand(static_cast<uint8_t>(FIXED_INT8_ARRAY_TYPE)));

[Rodolph Perfetta, 2016/04/07 14:13:50]

add/sub can handle any 8-bit constant directly, so remove this line, remove the
need for scratch2 and use the immediate in the sub below.

[binji, 2016/04/08 18:21:42]

Done.

+  __ sub(scratch, scratch, scratch2, SetCC);
+  __ Assert(ge, kOffsetOutOfRange);
+
+  Label abort;
+
+  {
+    Assembler::BlockConstPoolScope scope(masm);
+    __ add(pc, pc, Operand(scratch, LSL, 2));
+    __ nop();
+    __ b(i8);      // Int8Array
+    __ b(u8);      // Uint8Array
+    __ b(i16);     // Int16Array
+    __ b(u16);     // Uint16Array
+    __ b(i32);     // Int32Array
+    __ b(u32);     // Uint32Array
+    __ b(&abort);  // Float32Array
+    __ b(&abort);  // Float64Array
+    __ b(u8c);     // Uint8ClampedArray
+  }
+
+  __ bind(&abort);
+  __ Abort(kNoReason);
+}
+
+void ReturnInteger32(MacroAssembler* masm, DwVfpRegister dst, Register value,
+                     SwVfpRegister single_scratch, Label* use_heap_number) {
+  Label not_smi;
+  __ TrySmiTag(r0, value, &not_smi);
+  __ Ret();
+
+  __ bind(&not_smi);
+  __ vmov(single_scratch, value);
+  __ vcvt_f64_s32(dst, single_scratch);
+  __ jmp(use_heap_number);
+}
+
+void ReturnUnsignedInteger32(MacroAssembler* masm, DwVfpRegister dst,
+                             Register value, Register scratch,
+                             SwVfpRegister single_scratch,
+                             Label* use_heap_number) {
+  Label not_smi;
+  __ mov(scratch, Operand(0x40000000U));

[Rodolph Perfetta, 2016/04/07 14:13:49]

cmp can handle any 8-bit value with an even shift, so this line is not needed,
directly use the immediate in the cmp below.

[binji, 2016/04/08 18:21:42]

Done.

+  __ cmp(value, scratch);
+  __ b(cs, &not_smi);
+  __ SmiTag(r0, value);
+  __ Ret();
+
+  __ bind(&not_smi);
+  __ vmov(single_scratch, value);
+  __ vcvt_f64_u32(dst, single_scratch);
+  __ jmp(use_heap_number);
+}
+
+void ReturnAllocatedHeapNumber(MacroAssembler* masm, DwVfpRegister value,
+                               Register scratch, Register scratch2,
+                               Register scratch3) {
+  Label call_runtime;
+  __ LoadRoot(scratch3, Heap::kHeapNumberMapRootIndex);
+  __ AllocateHeapNumber(r0, scratch, scratch2, scratch3, &call_runtime);
+  __ vstr(value, FieldMemOperand(r0, HeapNumber::kValueOffset));
+  __ Ret();
+
+  __ bind(&call_runtime);
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    __ CallRuntimeSaveDoubles(Runtime::kAllocateHeapNumber);
+    __ vstr(value, FieldMemOperand(r0, HeapNumber::kValueOffset));
+  }
+  __ Ret();
+}
+
+}  // anonymous namespace
+
+void AtomicsLoadStub::Generate(MacroAssembler* masm) {
+  Register object = r1;
+  Register index = r0;  // Index is an untagged word32.
+  Register backing_store = r2;
+  Label i8, u8, i16, u16, i32, u32;
+
+  GetTypedArrayBackingStore(masm, backing_store, object, r3, d0);
+  TypedArrayJumpTable(masm, object, r3, r4, &i8, &u8, &i16, &u16, &i32, &u32,
+                      &u8);
+
+  __ bind(&i8);
+  __ ldrb(r0, MemOperand(backing_store, index));

[Rodolph Perfetta, 2016/04/07 14:13:50]

if you use ldrsb, then no need to use sxtb below

[binji, 2016/04/08 18:21:42]

Done.

+  __ dmb(ISH);
+  __ sxtb(r0, r0);
+  __ SmiTag(r0);
+  __ Ret();
+
+  __ bind(&u8);
+  __ ldrb(r0, MemOperand(backing_store, index));
+  __ dmb(ISH);
+  __ SmiTag(r0);
+  __ Ret();
+
+  __ bind(&i16);
+  __ ldrh(r0, MemOperand(backing_store, index, LSL, 1));

[Rodolph Perfetta, 2016/04/07 14:13:49]

use ldrsh to avoid the sxth below

[binji, 2016/04/08 18:21:42]

Done.

+  __ dmb(ISH);
+  __ sxth(r0, r0);
+  __ SmiTag(r0);
+  __ Ret();
+
+  __ bind(&u16);
+  __ ldrh(r0, MemOperand(backing_store, index, LSL, 1));
+  __ dmb(ISH);
+  __ SmiTag(r0);
+  __ Ret();
+
+  Label use_heap_number;
+
+  __ bind(&i32);
+  __ ldr(r0, MemOperand(backing_store, index, LSL, 2));
+  __ dmb(ISH);
+  ReturnInteger32(masm, d0, r0, s2, &use_heap_number);
+
+  __ bind(&u32);
+  __ ldr(r0, MemOperand(backing_store, index, LSL, 2));
+  __ dmb(ISH);
+  ReturnUnsignedInteger32(masm, d0, r0, r1, s2, &use_heap_number);
+
+  __ bind(&use_heap_number);
+  ReturnAllocatedHeapNumber(masm, d0, r1, r2, r3);
+}
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM