[crankshaft] Fragmentation-free allocation folding.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index fb15302308e6a32e89b14d76d6f0b77732f5756c..12348ced873fd9caeeeebb640e24d858fb8f80fd 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1527,6 +1527,7 @@ void MacroAssembler::Allocate(int object_size,
                               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.
@@ -1568,6 +1569,7 @@ void MacroAssembler::Allocate(int object_size,
 
   // 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);
   }
@@ -1575,8 +1577,10 @@ void MacroAssembler::Allocate(int 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));
@@ -1598,6 +1602,8 @@ void MacroAssembler::Allocate(int header_size,
                               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.
@@ -1649,9 +1655,9 @@ void MacroAssembler::Allocate(int header_size,
   } 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);
 
@@ -1659,7 +1665,6 @@ void MacroAssembler::Allocate(int header_size,
   DCHECK(kHeapObjectTag == 1);
   inc(result);
 
-  // Update allocation top.
   UpdateAllocationTopHelper(result_end, scratch, flags);
 }
 
@@ -1671,6 +1676,7 @@ void MacroAssembler::Allocate(Register object_size,
                               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.
@@ -1699,7 +1705,7 @@ void MacroAssembler::Allocate(Register object_size,
     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);
     }
@@ -1714,7 +1720,6 @@ void MacroAssembler::Allocate(Register object_size,
     mov(result_end, object_size);
   }
   add(result_end, result);
-  j(carry, gc_required);
   cmp(result_end, Operand::StaticVariable(allocation_limit));
   j(above, gc_required);
 
@@ -1722,8 +1727,58 @@ void MacroAssembler::Allocate(Register object_size,
   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);
 }