Fix fp problems in runtime code on ARM EABI by 8-byte aligning...

src/arm/macro-assembler-arm.cc

 // Copyright 2006-2008 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 273 matching lines @@
 
   // Drop the execution stack down to the frame pointer and restore
   // the caller frame pointer and return address.
   mov(sp, fp);
   ldm(ia_w, sp, fp.bit() | lr.bit());
 }
 
 
 void MacroAssembler::EnterExitFrame(StackFrame::Type type) {
   ASSERT(type == StackFrame::EXIT || type == StackFrame::EXIT_DEBUG);
+
+  // Compute the argv pointer and keep it in a callee-saved register.
+  // r0 is argc.
+  add(r6, sp, Operand(r0, LSL, kPointerSizeLog2));
+  sub(r6, r6, Operand(kPointerSize));
+
   // Compute parameter pointer before making changes and save it as ip
   // register so that it is restored as sp register on exit, thereby
   // popping the args.
 
   // ip = sp + kPointerSize * #args;
   add(ip, sp, Operand(r0, LSL, kPointerSizeLog2));

[Mark Lam, 2009/05/21 22:55:36]

This "add" instruction is functionally equivalent to the "add" at line 297.  You
can optimize the above 3 instructions slightly into the following 2
instructions:

add(ip, sp, Operand(r0, LSL, kPointerSizeLog2));
sub(r6, ip, Operand(kPointerSize));

 
+  // Align the stack at this point.  After this point we have 5 pushes,
+  // so in fact we have to unalign here!  See also the assert on the
+  // alignment immediately below.
+  if (OS::ActivationFrameAlignment() != kPointerSize) {
+    // This code needs to be made more general if this assert doesn't hold.
+    ASSERT(OS::ActivationFrameAlignment() == 2 * kPointerSize);
+    mov(r7, Operand(Smi::FromInt(0)));
+    tst(sp, Operand(OS::ActivationFrameAlignment() - 1));
+    push(r7, eq);  // Conditional push instruction.
+  }
+
   // Push in reverse order: caller_fp, sp_on_exit, and caller_pc.
   stm(db_w, sp, fp.bit() | ip.bit() | lr.bit());
   mov(fp, Operand(sp));  // setup new frame pointer
 
   // Push debug marker.
   mov(ip, Operand(type == StackFrame::EXIT_DEBUG ? 1 : 0));
   push(ip);
 
   // Save the frame pointer and the context in top.
   mov(ip, Operand(ExternalReference(Top::k_c_entry_fp_address)));
   str(fp, MemOperand(ip));
   mov(ip, Operand(ExternalReference(Top::k_context_address)));
   str(cp, MemOperand(ip));
 
   // Setup argc and the builtin function in callee-saved registers.
   mov(r4, Operand(r0));
   mov(r5, Operand(r1));
 
-  // Compute the argv pointer and keep it in a callee-saved register.
-  add(r6, fp, Operand(r4, LSL, kPointerSizeLog2));
-  add(r6, r6, Operand(ExitFrameConstants::kPPDisplacement - kPointerSize));
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
   // Save the state of all registers to the stack from the memory
   // location. This is needed to allow nested break points.
   if (type == StackFrame::EXIT_DEBUG) {
     // Use sp as base to push.
     CopyRegistersFromMemoryToStack(sp, kJSCallerSaved);
   }
 #endif
 }
@@ skipping 600 matching lines @@
 #endif
   mov(r0, Operand(p0));
   push(r0);
   mov(r0, Operand(Smi::FromInt(p1 - p0)));
   push(r0);
   CallRuntime(Runtime::kAbort, 2);
   // will not return here
 }
 
 } }  // namespace v8::internal