RFR(S): 8206075: add assertion for unbound assembler Labels for x86

[Hohensee, Paul]

Imo it's still good hygiene to require that Labels be bound if they're used, even if the generated code will never be executed. E.g., code that generates code for sizing purposes may be repurposed to generate executable code, in which case an unbound label may be a lurking bug. Also, I'm unaware (I may be corrected!) of any situation where bailing out happens in such a way as to both leave a Label unbound and execute its destructor. Even if there are, I'd say that'd be indicative of another real problem, such as code buffer overflow, so no harm would result.

Thanks,

Paul

On 7/11/18, 3:41 AM, "hotspot-runtime-dev on behalf of Doerr, Martin" <hotspot-runtime-dev-bounces at openjdk.java.net on behalf of martin.doerr at sap.com> wrote:

    Hi,
    
    I think the idea is good, but doesn't work in all cases.
    We may bail out from code generation and discard the generated code leaving the label unbound.
    We also may generate code with the purpose to determine its size. We don't need to bind labels because the code will never get executed.
    
    Best regards,
    Martin
    
    
    -----Original Message-----
    From: hotspot-runtime-dev [mailto:hotspot-runtime-dev-bounces at openjdk.java.net] On Behalf Of Vladimir Kozlov
    Sent: Mittwoch, 11. Juli 2018 03:34
    To: Liu Xin <navy.xliu at gmail.com>; hotspot-runtime-dev at openjdk.java.net
    Subject: Re: RFR(S): 8206075: add assertion for unbound assembler Labels for x86
    
    I hit new assert in few other tests:
    
    compiler/codegen/TestCharVect2.java
    compiler/c2/cr6340864/*
    
    Regards,
    Vladimir
    
    On 7/10/18 5:08 PM, Vladimir Kozlov wrote:
    > Fix looks reasonable. I will test it in our framework.
    > 
    > Thanks,
    > Vladimir
    > 
    > On 7/10/18 9:50 AM, Liu Xin wrote:
    >> Hi, Community,
    >> Could you please review this small patch?
    >> Bug:  https://bugs.openjdk.java.net/browse/JDK-8206075 
    >> <https://bugs.openjdk.java.net/browse/JDK-8206075>
    >> CR:  http://cr.openjdk.java.net/~phh/8206075/webrev.00/ 
    >> <http://cr.openjdk.java.net/~phh/8206075/webrev.00/>
    >> Problem:
    >> X86-32/64 will leave an unbound label if UseOnStackReplacement is OFF.
    >> This patch align up x86 with other architectures(ppc, arm).
    >> Add an assertion to the destructor of Label. It  will be wiped out in release build.
    >> Previously, hotspot cannot pass this test with assertion on x86-64.
    >> make run-test TEST=test/hotspot/jtreg/compiler/c1/Test7090976.java
    >> If this CR is approved, Paul Hohensee will push it.
    >> Thanks,
    >> --lx
    >>