Add a trap_on_abort flag

By setting this flag assertions behind --debug-code will trigger a
breakpoint instead of a call into Abort. This eases debugging, as the
call site is less cluttered and the backtrace starts where it should.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23352004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16319 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/macro-assembler-arm.cc

@@ -2847,6 +2847,11 @@ void MacroAssembler::Abort(BailoutReason reason) {
     RecordComment("Abort message: ");
     RecordComment(msg);
   }
+
+  if (FLAG_trap_on_abort) {
+    stop(msg);
+    return;
+  }
 #endif
 
   mov(r0, Operand(p0));

src/flag-definitions.h

@@ -703,13 +703,14 @@ DEFINE_bool(stress_compaction, false,
 DEFINE_bool(enable_slow_asserts, false,
             "enable asserts that are slow to execute")
 
-// codegen-ia32.cc / codegen-arm.cc
+// codegen-ia32.cc / codegen-arm.cc / macro-assembler-*.cc
 DEFINE_bool(print_source, false, "pretty print source code")
 DEFINE_bool(print_builtin_source, false,
             "pretty print source code for builtins")
 DEFINE_bool(print_ast, false, "print source AST")
 DEFINE_bool(print_builtin_ast, false, "print source AST for builtins")
 DEFINE_string(stop_at, "", "function name where to insert a breakpoint")
+DEFINE_bool(trap_on_abort, false, "replace aborts by breakpoints")
 
 // compiler.cc
 DEFINE_bool(print_builtin_scopes, false, "print scopes for builtins")

src/ia32/macro-assembler-ia32.cc

@@ -2774,6 +2774,11 @@ void MacroAssembler::Abort(BailoutReason reason) {
     RecordComment("Abort message: ");
     RecordComment(msg);
   }
+
+  if (FLAG_trap_on_abort) {
+    int3();
+    return;
+  }
 #endif
 
   push(eax);

src/x64/macro-assembler-x64.cc

@@ -524,7 +524,13 @@ void MacroAssembler::Abort(BailoutReason reason) {
     RecordComment("Abort message: ");
     RecordComment(msg);
   }
+
+  if (FLAG_trap_on_abort) {
+    int3();
+    return;
+  }
 #endif
+
   push(rax);
   movq(kScratchRegister, p0, RelocInfo::NONE64);
   push(kScratchRegister);