Change ARM exit frame layout and alingment handling...

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
===================================================================
--- src/arm/code-stubs-arm.cc	(revision 6435)
+++ src/arm/code-stubs-arm.cc	(working copy)
@@ -1,4 +1,4 @@
-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -2557,8 +2557,7 @@
                               Label* throw_termination_exception,
                               Label* throw_out_of_memory_exception,
                               bool do_gc,
-                              bool always_allocate,
-                              int frame_alignment_skew) {
+                              bool always_allocate) {
   // r0: result parameter for PerformGC, if any
   // r4: number of arguments including receiver  (C callee-saved)
   // r5: pointer to builtin function  (C callee-saved)
@@ -2584,14 +2583,13 @@
   __ mov(r0, Operand(r4));
   __ mov(r1, Operand(r6));
 
+#if defined(V8_HOST_ARCH_ARM)
   int frame_alignment = MacroAssembler::ActivationFrameAlignment();
   int frame_alignment_mask = frame_alignment - 1;
-#if defined(V8_HOST_ARCH_ARM)
   if (FLAG_debug_code) {
     if (frame_alignment > kPointerSize) {
       Label alignment_as_expected;
       ASSERT(IsPowerOf2(frame_alignment));
-      __ sub(r2, sp, Operand(frame_alignment_skew));
       __ tst(r2, Operand(frame_alignment_mask));
       __ b(eq, &alignment_as_expected);
       // Don't use Check here, as it will call Runtime_Abort re-entering here.
@@ -2601,36 +2599,17 @@
   }
 #endif
 
-  // Just before the call (jump) below lr is pushed, so the actual alignment is
-  // adding one to the current skew.
-  int alignment_before_call =
-      (frame_alignment_skew + kPointerSize) & frame_alignment_mask;
-  if (alignment_before_call > 0) {
-    // Push until the alignment before the call is met.
-    __ mov(r2, Operand(0, RelocInfo::NONE));
-    for (int i = alignment_before_call;
-        (i & frame_alignment_mask) != 0;
-        i += kPointerSize) {
-      __ push(r2);
-    }
-  }
-
   // TODO(1242173): To let the GC traverse the return address of the exit
   // frames, we need to know where the return address is. Right now,
-  // we push it on the stack to be able to find it again, but we never
+  // we store it on the stack to be able to find it again, but we never
   // restore from it in case of changes, which makes it impossible to
   // support moving the C entry code stub. This should be fixed, but currently
   // this is OK because the CEntryStub gets generated so early in the V8 boot
   // sequence that it is not moving ever.
   masm->add(lr, pc, Operand(4));  // Compute return address: (pc + 8) + 4

[Mads Ager (chromium), 2011/01/24 18:21:08]

You haven't changed this, but where is the '+ 8'?

[Søren Thygesen Gjesse, 2011/01/25 07:48:39]

The '+ 8' refers to that the pc is already at '+ 8' from the current
instruction. Rephrased the comment.

-  masm->push(lr);
+  __ str(lr, MemOperand(sp, 0));
   masm->Jump(r5);
 
-  // Restore sp back to before aligning the stack.
-  if (alignment_before_call > 0) {
-    __ add(sp, sp, Operand(alignment_before_call));
-  }
-
   if (always_allocate) {
     // It's okay to clobber r2 and r3 here. Don't mess with r0 and r1
     // though (contain the result).
@@ -2717,8 +2696,7 @@
                &throw_termination_exception,
                &throw_out_of_memory_exception,
                false,
-               false,
-               -kPointerSize);
+               false);
 
   // Do space-specific GC and retry runtime call.
   GenerateCore(masm,
@@ -2726,8 +2704,7 @@
                &throw_termination_exception,
                &throw_out_of_memory_exception,
                true,
-               false,
-               0);
+               false);
 
   // Do full GC and retry runtime call one final time.
   Failure* failure = Failure::InternalError();
@@ -2737,8 +2714,7 @@
                &throw_termination_exception,
                &throw_out_of_memory_exception,
                true,
-               true,
-               kPointerSize);
+               true);
 
   __ bind(&throw_out_of_memory_exception);
   GenerateThrowUncatchable(masm, OUT_OF_MEMORY);