[crankshaft] Fragmentation-free allocation folding.

src/crankshaft/ia32/lithium-codegen-ia32.cc

Index: src/crankshaft/ia32/lithium-codegen-ia32.cc
diff --git a/src/crankshaft/ia32/lithium-codegen-ia32.cc b/src/crankshaft/ia32/lithium-codegen-ia32.cc
index 179e6402ff673241fbe1fc4a8ff255384f71fa96..0044f414481d9ced472484986152548408e096c6 100644
--- a/src/crankshaft/ia32/lithium-codegen-ia32.cc
+++ b/src/crankshaft/ia32/lithium-codegen-ia32.cc
@@ -4870,6 +4870,14 @@ void LCodeGen::DoAllocate(LAllocate* instr) {
     flags = static_cast<AllocationFlags>(flags | PRETENURE);
   }
 
+  if (instr->hydrogen()->IsAllocationFoldingDominator()) {
+    flags = static_cast<AllocationFlags>(flags | ALLOCATION_FOLDING_DOMINATOR);
+  }
+
+  if (instr->hydrogen()->IsAllocationFolded()) {
+    flags = static_cast<AllocationFlags>(flags | ALLOCATION_FOLDED);
+  }
+
   if (instr->size()->IsConstantOperand()) {
     int32_t size = ToInteger32(LConstantOperand::cast(instr->size()));
     CHECK(size <= Page::kMaxRegularHeapObjectSize);
@@ -4899,6 +4907,30 @@ void LCodeGen::DoAllocate(LAllocate* instr) {
   }
 }
 
+void LCodeGen::DoFastAllocate(LFastAllocate* instr) {
+  DCHECK(instr->hydrogen()->IsAllocationFolded());
+  Register result = ToRegister(instr->result());
+  Register temp = ToRegister(instr->temp());
+
+  AllocationFlags flags = NO_ALLOCATION_FLAGS;
+  if (instr->hydrogen()->MustAllocateDoubleAligned()) {
+    flags = static_cast<AllocationFlags>(flags | DOUBLE_ALIGNMENT);
+  }
+  if (instr->hydrogen()->IsOldSpaceAllocation()) {
+    DCHECK(!instr->hydrogen()->IsNewSpaceAllocation());
+    flags = static_cast<AllocationFlags>(flags | PRETENURE);
+  }
+  if (!instr->hydrogen()->IsAllocationFoldingDominator()) {
+    if (instr->size()->IsConstantOperand()) {
+      int32_t size = ToInteger32(LConstantOperand::cast(instr->size()));
+      CHECK(size <= Page::kMaxRegularHeapObjectSize);
+      __ FastAllocate(size, result, temp, flags);
+    } else {
+      Register size = ToRegister(instr->size());
+      __ FastAllocate(size, result, temp, flags);
+    }
+  }
+}
 
 void LCodeGen::DoDeferredAllocate(LAllocate* instr) {
   Register result = ToRegister(instr->result());
@@ -4938,6 +4970,22 @@ void LCodeGen::DoDeferredAllocate(LAllocate* instr) {
   CallRuntimeFromDeferred(
       Runtime::kAllocateInTargetSpace, 2, instr, instr->context());
   __ StoreToSafepointRegisterSlot(result, eax);
+
+  if (instr->hydrogen()->IsAllocationFoldingDominator()) {
+    AllocationFlags allocation_flags = NO_ALLOCATION_FLAGS;
+    if (instr->hydrogen()->IsOldSpaceAllocation()) {
+      DCHECK(!instr->hydrogen()->IsNewSpaceAllocation());
+      allocation_flags = static_cast<AllocationFlags>(flags | PRETENURE);
+    }
+    // If the allocation folding dominator allocate triggered a GC, allocation
+    // happend in the runtime. We have to reset the top pointer to virtually
+    // undo the allocation.
+    ExternalReference allocation_top =
+        AllocationUtils::GetAllocationTopReference(isolate(), allocation_flags);
+    __ sub(eax, Immediate(kHeapObjectTag));
+    __ mov(Operand::StaticVariable(allocation_top), eax);

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

***~~~ landmine detected ~~~***

+    __ add(eax, Immediate(kHeapObjectTag));
+  }
 }