[crankshaft] Fragmentation-free allocation folding.

src/ia32/macro-assembler-ia32.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_IA32
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 1509 matching lines @@
 
 
 void MacroAssembler::Allocate(int object_size,
                               Register result,
                               Register result_end,
                               Register scratch,
                               Label* gc_required,
                               AllocationFlags flags) {
   DCHECK((flags & (RESULT_CONTAINS_TOP | SIZE_IN_WORDS)) == 0);
   DCHECK(object_size <= Page::kMaxRegularHeapObjectSize);
+  DCHECK((flags & ALLOCATION_FOLDED) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       mov(result, Immediate(0x7091));
       if (result_end.is_valid()) {
         mov(result_end, Immediate(0x7191));
       }
       if (scratch.is_valid()) {
         mov(scratch, Immediate(0x7291));
       }
@@ skipping 21 matching lines @@
       j(above_equal, gc_required);
     }
     mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   // Calculate new top and bail out if space is exhausted.
   Register top_reg = result_end.is_valid() ? result_end : result;
+
   if (!top_reg.is(result)) {
     mov(top_reg, result);
   }
   add(top_reg, Immediate(object_size));
   cmp(top_reg, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
-  // Update allocation top.
-  UpdateAllocationTopHelper(top_reg, scratch, flags);
+  if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
+    // The top pointer is not updated for allocation folding dominators.
+    UpdateAllocationTopHelper(top_reg, scratch, flags);
+  }
 
   if (top_reg.is(result)) {
     sub(result, Immediate(object_size - kHeapObjectTag));
   } else {
     // Tag the result.
     DCHECK(kHeapObjectTag == 1);
     inc(result);
   }
 }
 
 
 void MacroAssembler::Allocate(int header_size,
                               ScaleFactor element_size,
                               Register element_count,
                               RegisterValueType element_count_type,
                               Register result,
                               Register result_end,
                               Register scratch,
                               Label* gc_required,
                               AllocationFlags flags) {
   DCHECK((flags & SIZE_IN_WORDS) == 0);
+  DCHECK((flags & ALLOCATION_FOLDING_DOMINATOR) == 0);
+  DCHECK((flags & ALLOCATION_FOLDED) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       mov(result, Immediate(0x7091));
       mov(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         mov(scratch, Immediate(0x7291));
       }
       // Register element_count is not modified by the function.
     }
@@ skipping 31 matching lines @@
   if (element_count_type == REGISTER_VALUE_IS_SMI) {
     STATIC_ASSERT(static_cast<ScaleFactor>(times_2 - 1) == times_1);
     STATIC_ASSERT(static_cast<ScaleFactor>(times_4 - 1) == times_2);
     STATIC_ASSERT(static_cast<ScaleFactor>(times_8 - 1) == times_4);
     DCHECK(element_size >= times_2);
     DCHECK(kSmiTagSize == 1);
     element_size = static_cast<ScaleFactor>(element_size - 1);
   } else {
     DCHECK(element_count_type == REGISTER_VALUE_IS_INT32);
   }
+
   lea(result_end, Operand(element_count, element_size, header_size));
   add(result_end, result);
-  j(carry, gc_required);
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
   // Tag result.
   DCHECK(kHeapObjectTag == 1);
   inc(result);
 
-  // Update allocation top.
   UpdateAllocationTopHelper(result_end, scratch, flags);
 }
 
 
 void MacroAssembler::Allocate(Register object_size,
                               Register result,
                               Register result_end,
                               Register scratch,
                               Label* gc_required,
                               AllocationFlags flags) {
   DCHECK((flags & (RESULT_CONTAINS_TOP | SIZE_IN_WORDS)) == 0);
+  DCHECK((flags & ALLOCATION_FOLDED) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       mov(result, Immediate(0x7091));
       mov(result_end, Immediate(0x7191));
       if (scratch.is_valid()) {
         mov(scratch, Immediate(0x7291));
       }
       // object_size is left unchanged by this function.
     }
     jmp(gc_required);
     return;
   }
   DCHECK(!result.is(result_end));
 
   // Load address of new object into result.
   LoadAllocationTopHelper(result, scratch, flags);
 
   ExternalReference allocation_limit =
       AllocationUtils::GetAllocationLimitReference(isolate(), flags);
 
   // Align the next allocation. Storing the filler map without checking top is
   // safe in new-space because the limit of the heap is aligned there.
   if ((flags & DOUBLE_ALIGNMENT) != 0) {
     DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
     Label aligned;
     test(result, Immediate(kDoubleAlignmentMask));
     j(zero, &aligned, Label::kNear);
-    if ((flags & PRETENURE) != 0) {
+    if (((flags & ALLOCATION_FOLDED) == 0) && ((flags & PRETENURE) != 0)) {

[Michael Lippautz, 2016/05/10 08:32:58]

This does not make sense. We should never be in Allocate with ALLOCATION_FOLDED
== 1.

[Hannes Payer (out of office), 2016/05/10 09:04:45]

leftover, removed.

       cmp(result, Operand::StaticVariable(allocation_limit));
       j(above_equal, gc_required);
     }
     mov(Operand(result, 0),
         Immediate(isolate()->factory()->one_pointer_filler_map()));
     add(result, Immediate(kDoubleSize / 2));
     bind(&aligned);
   }
 
   // Calculate new top and bail out if space is exhausted.
   if (!object_size.is(result_end)) {
     mov(result_end, object_size);
   }
   add(result_end, result);
-  j(carry, gc_required);
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
   // Tag result.
   DCHECK(kHeapObjectTag == 1);
   inc(result);
 
-  // Update allocation top.
-  UpdateAllocationTopHelper(result_end, scratch, flags);
+  if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
+    // The top pointer is not updated for allocation folding dominators.
+    UpdateAllocationTopHelper(result_end, scratch, flags);
+  }
+}
+
+void MacroAssembler::FastAllocate(int object_size, Register result,
+                                  Register result_end, AllocationFlags flags) {
+  DCHECK(!result.is(result_end));
+  // Load address of new object into result.
+  LoadAllocationTopHelper(result, no_reg, flags);
+
+  if ((flags & DOUBLE_ALIGNMENT) != 0) {
+    DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
+    Label aligned;
+    test(result, Immediate(kDoubleAlignmentMask));
+    j(zero, &aligned, Label::kNear);
+    mov(Operand(result, 0),
+        Immediate(isolate()->factory()->one_pointer_filler_map()));
+    add(result, Immediate(kDoubleSize / 2));
+    bind(&aligned);
+  }
+
+  lea(result_end, Operand(result, object_size));
+  UpdateAllocationTopHelper(result_end, no_reg, flags);
+
+  DCHECK(kHeapObjectTag == 1);
+  inc(result);
+}
+
+void MacroAssembler::FastAllocate(Register object_size, Register result,
+                                  Register result_end, AllocationFlags flags) {
+  DCHECK(!result.is(result_end));
+  // Load address of new object into result.
+  LoadAllocationTopHelper(result, no_reg, flags);
+
+  if ((flags & DOUBLE_ALIGNMENT) != 0) {
+    DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
+    Label aligned;
+    test(result, Immediate(kDoubleAlignmentMask));
+    j(zero, &aligned, Label::kNear);
+    mov(Operand(result, 0),
+        Immediate(isolate()->factory()->one_pointer_filler_map()));
+    add(result, Immediate(kDoubleSize / 2));
+    bind(&aligned);
+  }
+
+  lea(result_end, Operand(result, object_size, times_1, 0));
+  UpdateAllocationTopHelper(result_end, no_reg, flags);
+
+  DCHECK(kHeapObjectTag == 1);
+  inc(result);
 }
 
 
 void MacroAssembler::AllocateHeapNumber(Register result,
                                         Register scratch1,
                                         Register scratch2,
                                         Label* gc_required,
                                         MutableMode mode) {
   // Allocate heap number in new space.
   Allocate(HeapNumber::kSize, result, scratch1, scratch2, gc_required,
@@ skipping 1663 matching lines @@
   mov(eax, dividend);
   shr(eax, 31);
   add(edx, eax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32