Detect simple tail calls

src/compiler/linkage.h

Index: src/compiler/linkage.h
diff --git a/src/compiler/linkage.h b/src/compiler/linkage.h
index fa34adb7c2e0926f9579eecaac86a22efe2f76ff..6926ffb64e344ae9d9742b78d11cc18d455ee5c9 100644
--- a/src/compiler/linkage.h
+++ b/src/compiler/linkage.h
@@ -27,6 +27,10 @@ class LinkageLocation {
  public:
   explicit LinkageLocation(int location) : location_(location) {}
 
+  bool is_register() const {
+    return 0 <= location_ && location_ <= ANY_REGISTER;
+  }
+
   static const int16_t ANY_REGISTER = 1023;
   static const int16_t MAX_STACK_SLOT = 32767;
 
@@ -61,6 +65,7 @@ class CallDescriptor final : public ZoneObject {
     kPatchableCallSite = 1u << 1,
     kNeedsNopAfterCall = 1u << 2,
     kHasExceptionHandler = 1u << 3,
+    kIsTailCallAllowed = 1u << 4,

[Benedikt Meurer, 2015/04/29 04:06:05]

Can we rename this to kSupportsTailCalls?

[Sven Panne, 2015/04/29 10:24:18]

Done.

     kPatchableCallSiteWithNop = kPatchableCallSite | kNeedsNopAfterCall
   };
   typedef base::Flags<Flag> Flags;
@@ -108,6 +113,7 @@ class CallDescriptor final : public ZoneObject {
   Flags flags() const { return flags_; }
 
   bool NeedsFrameState() const { return flags() & kNeedsFrameState; }
+  bool IsTailCallAllowed() const { return flags() & kIsTailCallAllowed; }

[Benedikt Meurer, 2015/04/29 04:06:05]

SupportsTailCalls?

[Sven Panne, 2015/04/29 10:24:18]

Done.

 
   LinkageLocation GetReturnLocation(size_t index) const {
     return location_sig_->GetReturn(index);
@@ -137,6 +143,8 @@ class CallDescriptor final : public ZoneObject {
 
   const char* debug_name() const { return debug_name_; }
 
+  bool UsesOnlyRegisters() const;
+
  private:
   friend class Linkage;