S390: [crankshaft] Fragmentation-free allocation folding.

src/s390/macro-assembler-s390.cc

 // Copyright 2014 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.
 
 #include <assert.h>  // For assert
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #if V8_TARGET_ARCH_S390
 
 #include "src/base/bits.h"
@@ skipping 1688 matching lines @@
   // Get the value at the masked, scaled index and return.
   const int kValueOffset =
       SeededNumberDictionary::kElementsStartOffset + kPointerSize;
   LoadP(result, FieldMemOperand(t2, kValueOffset));
 }
 
 void MacroAssembler::Allocate(int object_size, Register result,
                               Register scratch1, Register scratch2,
                               Label* gc_required, AllocationFlags flags) {
   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.
       LoadImmP(result, Operand(0x7091));
       LoadImmP(scratch1, Operand(0x7191));
       LoadImmP(scratch2, Operand(0x7291));
     }
     b(gc_required);
     return;
   }
@@ skipping 66 matching lines @@
   if (is_int16(object_size)) {
     CmpP(r0, Operand(object_size));
     blt(gc_required);
     AddP(result_end, result, Operand(object_size));
   } else {
     mov(result_end, Operand(object_size));
     CmpP(r0, result_end);
     blt(gc_required);
     AddP(result_end, result, result_end);
   }
-  StoreP(result_end, MemOperand(top_address));
+
+  if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
+    // The top pointer is not updated for allocation folding dominators.
+    StoreP(result_end, MemOperand(top_address));
+  }
 
   // Tag object.
   AddP(result, result, Operand(kHeapObjectTag));
 }
 
 void MacroAssembler::Allocate(Register object_size, Register result,
                               Register result_end, Register scratch,
                               Label* gc_required, AllocationFlags flags) {
+  DCHECK((flags & ALLOCATION_FOLDED) == 0);
   if (!FLAG_inline_new) {
     if (emit_debug_code()) {
       // Trash the registers to simulate an allocation failure.
       LoadImmP(result, Operand(0x7091));
       LoadImmP(scratch, Operand(0x7191));
       LoadImmP(result_end, Operand(0x7291));
     }
     b(gc_required);
     return;
   }
@@ skipping 69 matching lines @@
     CmpP(r0, object_size);
     blt(gc_required);
     AddP(result_end, result, object_size);
   }
 
   // Update allocation top. result temporarily holds the new top.
   if (emit_debug_code()) {
     AndP(r0, result_end, Operand(kObjectAlignmentMask));
     Check(eq, kUnalignedAllocationInNewSpace, cr0);
   }
+  if ((flags & ALLOCATION_FOLDING_DOMINATOR) == 0) {
+    // The top pointer is not updated for allocation folding dominators.
+    StoreP(result_end, MemOperand(top_address));
+  }
+
+  // Tag object.
+  AddP(result, result, Operand(kHeapObjectTag));
+}
+
+void MacroAssembler::FastAllocate(Register object_size, Register result,
+                                  Register result_end, Register scratch,
+                                  AllocationFlags flags) {
+  // |object_size| and |result_end| may overlap if the DOUBLE_ALIGNMENT flag
+  // is not specified. Other registers must not overlap.
+  DCHECK(!AreAliased(object_size, result, scratch, ip));
+  DCHECK(!AreAliased(result_end, result, scratch, ip));
+  DCHECK((flags & DOUBLE_ALIGNMENT) == 0 || !object_size.is(result_end));
+
+  ExternalReference allocation_top =
+      AllocationUtils::GetAllocationTopReference(isolate(), flags);
+
+  Register top_address = scratch;
+  mov(top_address, Operand(allocation_top));
+  LoadP(result, MemOperand(top_address));
+
+  if ((flags & DOUBLE_ALIGNMENT) != 0) {
+// 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 V8_TARGET_ARCH_S390X
+    STATIC_ASSERT(kPointerAlignment == kDoubleAlignment);
+#else
+    DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
+    AndP(result_end, result, Operand(kDoubleAlignmentMask));
+    Label aligned;
+    beq(&aligned);

[JoranSiu, 2016/05/13 00:53:59]

CAn you add a Label::kNear here?

+    mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
+    StoreW(result_end, MemOperand(result));
+    AddP(result, result, Operand(kDoubleSize / 2));
+    bind(&aligned);
+#endif
+  }
+
+  // Calculate new top using result. Object size may be in words so a shift is
+  // required to get the number of bytes.
+  if ((flags & SIZE_IN_WORDS) != 0) {
+    ShiftLeftP(result_end, object_size, Operand(kPointerSizeLog2));
+    AddP(result_end, result, result_end);
+  } else {
+    AddP(result_end, result, object_size);
+  }
+
+  // Update allocation top. result temporarily holds the new top.
+  if (emit_debug_code()) {
+    AndP(r0, result_end, Operand(kObjectAlignmentMask));
+    Check(eq, kUnalignedAllocationInNewSpace, cr0);
+  }
   StoreP(result_end, MemOperand(top_address));
 
   // Tag object.
+  AddP(result, result, Operand(kHeapObjectTag));
+}
+
+void MacroAssembler::FastAllocate(int object_size, Register result,
+                                  Register scratch1, Register scratch2,
+                                  AllocationFlags flags) {
+  DCHECK(object_size <= Page::kMaxRegularHeapObjectSize);
+  DCHECK(!AreAliased(result, scratch1, scratch2, ip));
+
+  // Make object size into bytes.
+  if ((flags & SIZE_IN_WORDS) != 0) {
+    object_size *= kPointerSize;
+  }
+  DCHECK_EQ(0, object_size & kObjectAlignmentMask);
+
+  ExternalReference allocation_top =
+      AllocationUtils::GetAllocationTopReference(isolate(), flags);
+
+  // Set up allocation top address register.
+  Register top_address = scratch1;
+  Register result_end = scratch2;
+  mov(top_address, Operand(allocation_top));
+  LoadP(result, MemOperand(top_address));
+
+  if ((flags & DOUBLE_ALIGNMENT) != 0) {
+// 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 V8_TARGET_ARCH_S390X
+    STATIC_ASSERT(kPointerAlignment == kDoubleAlignment);
+#else
+    DCHECK(kPointerAlignment * 2 == kDoubleAlignment);
+    AndP(result_end, result, Operand(kDoubleAlignmentMask));
+    Label aligned;
+    beq(&aligned);

[JoranSiu, 2016/05/13 00:53:59]

Label::kNear here too.

+    mov(result_end, Operand(isolate()->factory()->one_pointer_filler_map()));
+    StoreW(result_end, MemOperand(result));
+    AddP(result, result, Operand(kDoubleSize / 2));
+    bind(&aligned);
+#endif
+  }
+
+  // Calculate new top using result.
+  AddP(result_end, result, Operand(object_size));
+
+  // The top pointer is not updated for allocation folding dominators.
+  StoreP(result_end, MemOperand(top_address));
+
+  // Tag object.
   AddP(result, result, Operand(kHeapObjectTag));
 }
 
 void MacroAssembler::AllocateTwoByteString(Register result, Register length,
                                            Register scratch1, Register scratch2,
                                            Register scratch3,
                                            Label* gc_required) {
   // Calculate the number of bytes needed for the characters in the string while
   // observing object alignment.
   DCHECK((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) == 0);
@@ skipping 3508 matching lines @@
   }
   if (mag.shift > 0) ShiftRightArith(result, result, Operand(mag.shift));
   ExtractBit(r0, dividend, 31);
   AddP(result, r0);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_S390