Add dynamic stack frame alignment to optimized functions with untagged doubles on the stack.

src/ia32/deoptimizer-ia32.cc

Index: src/ia32/deoptimizer-ia32.cc
diff --git a/src/ia32/deoptimizer-ia32.cc b/src/ia32/deoptimizer-ia32.cc
index 313b65f6e2168fe4fd0371083d103a90f493b83b..7779be389beb870f2886c4a131a13e568fc5baf3 100644
--- a/src/ia32/deoptimizer-ia32.cc
+++ b/src/ia32/deoptimizer-ia32.cc
@@ -440,6 +440,14 @@ void Deoptimizer::DoComputeOsrOutputFrame() {
   output_[0]->SetContinuation(
       reinterpret_cast<uint32_t>(continuation->entry()));
 
+  // All OSR stack frames are dynamically aligned to an 8-byte boundary.
+  int frame_pointer = output_[0]->GetRegister(ebp.code());

[Kevin Millikin (Chromium), 2011/09/23 09:38:49]

Don't put this here (i.e., don't set ebp register and then patch it up just
later).  It's too easy to miss what's going on.

Please just set it to the value you want in the first place, about 8 lines
above.

+  if ((frame_pointer & 0x4) == 0) {
+    // Return address at FP + 4 should be aligned, so FP mod 8 should be 4.
+    output_[0]->SetRegister(ebp.code(), frame_pointer - kPointerSize);
+    has_alignment_padding_ = 1;
+  }
+
   if (FLAG_trace_osr) {
     PrintF("[on-stack replacement translation %s: 0x%08" V8PRIxPTR " ",
            ok ? "finished" : "aborted",
@@ -490,6 +498,15 @@ void Deoptimizer::DoComputeFrame(TranslationIterator* iterator,
   // the input frame pointer and the output frame's height.  For all
   // subsequent output frames, it can be computed from the previous one's
   // top address and the current frame's size.
+
+  // If the optimized frame had alignment padding, adjust the frame pointer

[Kevin Millikin (Chromium), 2011/09/23 09:38:49]

I also don't like this here.  First, it breaks up the comment about setting the
top address so it's now far from the code that sets the top address.

Worse, I think it's a bug waiting to happen to just spoof the value in the input
ebp register.  I'd rather leave the correct value there and adjust for padding
in a couple of places.

[William Hesse, 2011/09/23 12:50:11]

Done.

+  // to point to the new position of the old frame pointer after padding
+  // is removed.
+  if (has_alignment_padding_ == 1) {
+    input_->SetRegister(ebp.code(),
+                        input_->GetRegister(ebp.code()) + kPointerSize);
+  }
+
   uint32_t top_address;
   if (is_bottommost) {
     // 2 = context and function in the frame.
@@ -734,6 +751,17 @@ void Deoptimizer::EntryGenerator::Generate() {
   __ cmp(ecx, Operand(esp));
   __ j(not_equal, &pop_loop);
 
+  // If frame was dynamically aligned, pop padding.
+  Label sentinel, sentinel_done;
+  __ pop(Operand(ecx));
+  __ cmp(ecx, Operand(eax, Deoptimizer::frame_alignment_marker_offset()));
+  __ j(equal, &sentinel);
+  __ push(Operand(ecx));
+  __ jmp(&sentinel_done);
+  __ bind(&sentinel);
+  __ mov(Operand(eax, Deoptimizer::has_alignment_padding_offset()),
+         Immediate(1));
+  __ bind(&sentinel_done);
   // Compute the output frame in the deoptimizer.
   __ push(eax);
   __ PrepareCallCFunction(1, ebx);
@@ -745,6 +773,17 @@ void Deoptimizer::EntryGenerator::Generate() {
   }
   __ pop(eax);
 
+  if (type() == OSR) {
+    // If alignment padding is added, push the sentinel.
+    Label no_osr_padding;
+    __ cmp(Operand(eax, Deoptimizer::has_alignment_padding_offset()),
+           Immediate(0));
+    __ j(equal, &no_osr_padding, Label::kNear);
+    __ push(Operand(eax, Deoptimizer::frame_alignment_marker_offset()));
+    __ bind(&no_osr_padding);
+  }
+
+
   // Replace the current frame with the output frames.
   Label outer_push_loop, inner_push_loop;
   // Outer loop state: eax = current FrameDescription**, edx = one past the