Direct call api functions (arm implementation)

src/arm/code-stubs-arm.cc

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@@ skipping 2686 matching lines @@
   // sp: stack pointer  (restored as callee's sp after C call)
   // cp: current context  (C callee-saved)
 
   // Result returned in r0 or r0+r1 by default.
 
   // NOTE: Invocations of builtins may return failure objects
   // instead of a proper result. The builtin entry handles
   // this by performing a garbage collection and retrying the
   // builtin once.
 
+  // r0 is argc.
+  // Compute callee's stack pointer before making changes and save it as
+  // ip register so that it is restored as sp register on exit, thereby
+  // popping the args.

[antonm, 2011/01/21 17:56:36]

I think you should add a reference to EnterExitFrame, something like
"EnterExitFrame below will store ip as sp on exit"---it was obvious when it was
in the same macro, but not now

[Zaheer, 2011/01/24 09:43:31]

Done.

+
+  // ip = sp + kPointerSize * #args;
+  __ add(ip, sp, Operand(r0, LSL, kPointerSizeLog2));
+
+  // Compute the argv pointer and keep it in a callee-saved register.
+  __ sub(r6, ip, Operand(kPointerSize));
+
   // Enter the exit frame that transitions from JavaScript to C++.
-  __ EnterExitFrame(save_doubles_);
+  __ EnterExitFrame(save_doubles_, 1);  // 1 pending push after this call.
+
+  // Setup argc and the builtin function in callee-saved registers.
+  __ mov(r4, Operand(r0));
+  __ mov(r5, Operand(r1));

[Erik Corry, 2011/01/21 14:28:40]

I don't see the benefit of moving this outside the EnterExitFrame, but if you
are going to do it then you should update the comment in macro-assembler-arm.h.

[Zaheer, 2011/01/24 09:43:31]

Updated comment in macro-assembler-arm.h.

 
   // r4: number of arguments (C callee-saved)
   // r5: pointer to builtin function (C callee-saved)
   // r6: pointer to first argument (C callee-saved)
 
   Label throw_normal_exception;
   Label throw_termination_exception;
   Label throw_out_of_memory_exception;
 
   // Call into the runtime system.
@@ skipping 2255 matching lines @@
   __ LeaveInternalFrame();
   // Compute the entry point of the rewritten stub.
   __ add(r2, r0, Operand(Code::kHeaderSize - kHeapObjectTag));
   // Restore registers.
   __ pop(lr);
   __ pop(r0);
   __ pop(r1);
   __ Jump(r2);
 }
 
+void DirectCEntryStub::Generate(MacroAssembler* masm) {
+  __ ldr(pc, MemOperand(fp, ExitFrameConstants::kPCOffset));
+}
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM