PPC: [turbofan] Enable tail calls for %_CallRuntime.

Port 1fa4285e

Original commit message:
    This involves:
    - Enabling the tail call optimization reducer in all cases.
    - Adding an addition flag to CallFunctionParameters to mark call sites
      that can be tail-called enabled.
    - Only set the tail-call flag for %_CallFunction.

R=danno@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1224533002

Cr-Commit-Position: refs/heads/master@{#29453}

src/compiler/ppc/code-generator-ppc.cc

@@ -585,10 +585,7 @@ void CodeGenerator::AssembleDeconstructActivationRecord() {
   CallDescriptor* descriptor = linkage()->GetIncomingDescriptor();
   int stack_slots = frame()->GetSpillSlotCount();
   if (descriptor->IsJSFunctionCall() || stack_slots > 0) {
-    int pop_count = descriptor->IsJSFunctionCall()
-                        ? static_cast<int>(descriptor->JSParameterCount())
-                        : 0;
-    __ LeaveFrame(StackFrame::MANUAL, pop_count * kPointerSize);
+    __ LeaveFrame(StackFrame::MANUAL);
   }
 }
 
@@ -620,6 +617,9 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
                 Operand(Code::kHeaderSize - kHeapObjectTag));
         __ Jump(ip);
       } else {
+        // We cannot use the constant pool to load the target since
+        // we've already restored the caller's frame.
+        ConstantPoolUnavailableScope constant_pool_unavailable(masm());
         __ Jump(Handle<Code>::cast(i.InputHeapObject(0)),
                 RelocInfo::CODE_TARGET);
       }
@@ -1379,7 +1379,9 @@ void CodeGenerator::AssembleReturn() {
       __ bind(&return_label_);
       int pop_count = descriptor->IsJSFunctionCall()
                           ? static_cast<int>(descriptor->JSParameterCount())
-                          : 0;
+                          : (info()->IsStub()
+                                 ? info()->code_stub()->GetStackParameterCount()
+                                 : 0);
       __ LeaveFrame(StackFrame::MANUAL, pop_count * kPointerSize);
       __ Ret();
     }

src/compiler/ppc/instruction-selector-ppc.cc

@@ -1520,9 +1520,7 @@ void InstructionSelector::VisitTailCall(Node* node) {
   DCHECK_EQ(0, descriptor->flags() & CallDescriptor::kNeedsNopAfterCall);
 
   // TODO(turbofan): Relax restriction for stack parameters.
-  if (descriptor->UsesOnlyRegisters() &&
-      descriptor->HasSameReturnLocationsAs(
-          linkage()->GetIncomingDescriptor())) {
+  if (linkage()->GetIncomingDescriptor()->CanTailCall(node)) {
     CallBuffer buffer(zone(), descriptor, nullptr);
 
     // Compute InstructionOperands for inputs and outputs.
@@ -1531,8 +1529,6 @@ void InstructionSelector::VisitTailCall(Node* node) {
     // heuristics in the register allocator for where to emit constants.
     InitializeCallBuffer(node, &buffer, true, false);
 
-    DCHECK_EQ(0u, buffer.pushed_nodes.size());
-
     // Select the appropriate opcode based on the call type.
     InstructionCode opcode;
     switch (descriptor->kind()) {