RFR [XS] 8041658: Use of -fdevirtualize on macroAssembler_x86.o (via -O2) with gcc 4.9.0 creates broken VM

[Andrew Haley]

On 04/24/2014 10:42 AM, Volker Simonis wrote:

> could you pleas hold on a little bit.
> 
> I just found out that for x86_64 we additionally need -fno-devirtualize
> when compiling 'assembler_x86.cpp'. Without the option, the compilation of
> "Assembler::reachable(AddressLiteral adr)" is totally broken:
> 
>    0x7ffff6046910 <_ZN9Assembler9reachableE14AddressLiteral>:    push   %rbp
>    0x7ffff6046911 <_ZN9Assembler9reachableE14AddressLiteral+1>:    mov
> %rsp,%rbp
>    0x7ffff6046914:    data32 data32 nopw %cs:0x0(%rax,%rax,1)
>    0x7ffff6046920 <_ZN9Assembler19is_polling_page_farEv>:    mov
> 0x12d7e69(%rip),%rax
> 
> As you can see it only contains two instructions before it unconditionally
> falls into 'Assembler::is_polling_page_far()'
> 
> Maybe we should do some more thorough tests on both, x86 and x86_64 with
> these settings to avoid follow-up changes.
> 
> What bothers me however is the fact that we now get this sever error at
> several places in the OpenJDK while it doesn't seem to affect others and I
> can not see what's special in the coding that triggers the misbehavior?

I think I might be able to.  I'm debugging GCC now.

Andrew.