RFR: 8375311: Some builds are missing debug helpers

[Andrew Haley]

On Wed, 14 Jan 2026 15:32:28 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> [JDK-8318834](https://bugs.openjdk.org/browse/JDK-8318834) pointed out that on linux s390x, debug builds were missing debug helpers .
> This happened because we enabled some time ago linktime gc (-Wl,--gc-sections in the linker flags, plus -ffunction-sections -fdata-sections in compile flags) for linux x390x by default.
> But potentially ltgc or similar size-optimizing options could be enabled on other platforms too, and not only debug builds could lose the debug helpers (however in non-debug builds they might be not that important).
> 
> On Windows we already export the debug helper symbols, so it might be good to do this on other platforms, especially Linux, too.

This is a string of volatile stores. It'd be nice to get it fixed too.


   2.94%      │   │   ↘↘↘│││  0x0000ffff35382988:   movz		w0, #0, lsl #16
   1.26%      │   │      │││  0x0000ffff3538298c:   dmb		ish
   4.04%      │   │      │││  0x0000ffff35382990:   str		w0, [x1, #0xc]
              │   │      │││  0x0000ffff35382994:   dmb		ish                 ;*putfield intField1 {reexecute=0 rethrow=0 return_oop=0}
              │   │      │││                                                            ; - org.openjdk.bench.vm.compiler.PostAllocationStores$TestWithNullVolatileStores::<init>@21 (line 120)
   4.41%      │   │      │││  0x0000ffff35382998:   movz		w0, #0, lsl #16
              │   │      │││  0x0000ffff3538299c:   dmb		ish
   3.14%      │   │      │││  0x0000ffff353829a0:   str		w0, [x1, #0x18]
              │   │      │││  0x0000ffff353829a4:   dmb		ish                 ;*putfield intField2 {reexecute=0 rethrow=0 return_oop=0}
              │   │      │││                                                            ; - org.openjdk.bench.vm.compiler.PostAllocationStores$TestWithNullVolatileStores::<init>@26 (line 121)
   2.91%      │   │      │││  0x0000ffff353829a8:   mov		x0, #0
              │   │      │││  0x0000ffff353829ac:   dmb		ish
   1.75%      │   │      │││  0x0000ffff353829b0:   str		x0, [x1, #0x10]
              │   │      │││  0x0000ffff353829b4:   dmb		ish                 ;*putfield longField1 {reexecute=0 rethrow=0 return_oop=0}
              │   │      │││                                                            ; - org.openjdk.bench.vm.compiler.PostAllocationStores$TestWithNullVolatileStores::<in

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PR Comment: https://git.openjdk.org/jdk/pull/29232#issuecomment-3751164654