In cases where there is a constant in a stable object array, some IR nodes describing memory barriers are not eliminated despite the fact that access could be constant folded and the load is indeed elided.

static final List<Integer> LAZY_LIST = List.ofLazy(1, _ -> THE_VALUE);

    @Test
    @IR(failOn = { IRNode.LOAD, IRNode.MEMBAR })
    static int foldLazyList() {
        // Access should be folded.
        // No barriers expected for a folded access (as opposed to a non-folded).
        return LAZY_LIST.get(0);
    }

Compilations (2) of Failed Methods (2)
--------------------------------------
1) Compilation of "static int compiler.c2.irTests.stable.LazyConstantTest.foldLazyList()":
> Phase "PrintIdeal":
AFTER: PrintIdeal
   0 Root === 0 157 [[ 0 1 3 156 ]] inner
   1 Con === 0 [[ ]] #top
   3 Start === 3 0 [[ 3 5 6 7 8 9 ]] #{0:control, 1:abIO, 2:memory, 3:rawptr:BotPTR, 4:return_address}
   5 Parm === 3 [[ 114 ]] Control !jvms: LazyConstantTest::foldLazyList @ bci:-1 (line 78)
   6 Parm === 3 [[ 157 ]] I_O !jvms: LazyConstantTest::foldLazyList @ bci:-1 (line 78)
   7 Parm === 3 [[ 114 ]] Memory Memory: @ptr:BotPTR+bot, idx=Bot; !jvms: LazyConstantTest::foldLazyList @ bci:-1 (line 78)
   8 Parm === 3 [[ 157 ]] FramePtr !jvms: LazyConstantTest::foldLazyList @ bci:-1 (line 78)
   9 Parm === 3 [[ 157 ]] ReturnAdr !jvms: LazyConstantTest::foldLazyList @ bci:-1 (line 78)
 114 MemBarCPUOrder === 5 1 7 1 1 [[ 115 116 ]] !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 115 Proj === 114 [[ 122 ]] #0 !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 116 Proj === 114 [[ 122 ]] #2 Memory: @ptr:BotPTR+bot, idx=Bot; !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 122 MemBarCPUOrder === 115 1 116 1 1 [[ 123 124 ]] !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 123 Proj === 122 [[ 126 ]] #0 !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 124 Proj === 122 [[ 126 ]] #2 Memory: @ptr:BotPTR+bot, idx=Bot; !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 126 MemBarAcquire === 123 1 124 1 1 [[ 127 128 ]] !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 127 Proj === 126 [[ 157 ]] #0 !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 128 Proj === 126 [[ 157 ]] #2 Memory: @ptr:BotPTR+bot, idx=Bot; !jvms: LazyCollections$LazyList::contentsAcquire @ bci:8 (line 136) LazyCollections$LazyList::get @ bci:13 (line 82) LazyConstantTest::foldLazyList @ bci:4 (line 78)
 156 ConI === 0 [[ 157 ]] #int:42
 157 Return === 127 6 128 8 9 returns 156 [[ 0 ]]

It appears to be the case that such fences _do_ get eliminated if we do a stable _field access_ but not an _array access_.

A complete reproducer can be found here:

https://github.com/openjdk/jdk/blob/eb2c2974e3cf2d1d4d28f9cd935363d13e8a3b93/test/hotspot/jtreg/compiler/c2/irTests/stable/LazyConstantsIrTest.java