RFR: 8370200: Crash: assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1) failed: only phis

[Roberto Castañeda Lozano]

On Fri, 5 Dec 2025 11:49:29 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> The crash occurs because verification code expects the inner and outer
> loop of a loop strip mining nest to have the same number of phis but,
> in this case, the inner loop has one more memory phis than the outer
> loop.
> 
> 1) After `OuterStripMinedLoopNode::adjust_strip_mined_loop`, inner and
> outer loops have the same number of phis, as expected.
> 
> 
>  309  MergeMem  === _ 1 306 1 1 284  [[ 429 ]]  { - - N284:instptr:java/lang/Throwable (java/io/Serializable):BotPTR+20,iid=bot [narrow] }  Memory: @ptr:BotPTR+bot, idx=Bot; !orig=205 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
> 
>  248  OuterStripMinedLoop  === 248 321 247  [[ 248 249 428 429 430 ]] 
>  429  Phi  === 248 309 205  [[ 93 ]]  #memory  Memory: @ptr:BotPTR+bot, idx=Bot; !orig=93 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
>  430  Phi  === 248 306 121  [[ 94 ]]  #memory  Memory: @instptr:TestMismatchedMemoryPhis:BotPTR+16,iid=bot, name=l, idx=4; !orig=94 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
> 
>  249  CountedLoop  === 249 248 197  [[ 249 119 96 93 94 ]] inner stride: 1  strip mined !orig=[223],[91] !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
>   93  Phi  === 249 429 205  [[ 117 97 ]]  #memory  Memory: @ptr:BotPTR+bot, idx=Bot; !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
>   94  Phi  === 249 430 121  [[ 97 ]]  #memory  Memory: @instptr:TestMismatchedMemoryPhis:BotPTR+16,iid=bot, name=l, idx=4; !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
> 
> 
> 2) Then `PhiNode::Ideal` runs for 429 and pushed the `MergeMem` 309
> through the outer loop phi:
> 
> 
>  248  OuterStripMinedLoop  === 248 321 247  [[ 248 249 428 429 430 444 446 ]] 
>  430  Phi  === 248 306 121  [[ 94 ]]  #memory  Memory: @instptr:TestMismatchedMemoryPhis:BotPTR+16,iid=bot, name=l, idx=4; !orig=94 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
>  444  Phi  === 248 306 121  [[ 445 ]]  #memory  Memory: @ptr:BotPTR+bot, idx=Bot; !orig=429,93 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
>  446  Phi  === 248 284 170  [[ 445 ]]  #memory  Memory: @instptr:java/lang/Throwable (java/io/Serializable):BotPTR+20,iid=bot [narrow], name=detailMessage, idx=5; !orig=444,429,93 !jvms: TestMismatchedMemoryPhis::mainTest @ bci:37 (line 49)
> 
>  445  MergeMem  === _ 1 444 1 1 446  [[ 93 ]]  { - - N446:instptr:java/lang/Throwable (java/io/Serializable):BotPTR+20,iid=bot [narrow] }  Memory: @ptr:BotPTR+bot, idx=Bot; !orig=[429],93 !jvms: TestMismatchedMemoryPhis::mainTe...

Changes requested by rcastanedalo (Reviewer).

test/hotspot/jtreg/compiler/loopstripmining/TestMismatchedMemoryPhis.java line 28:

> 26:  * @bug 8370200
> 27:  * @summary Crash: assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1) failed: only phis
> 28:  * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:StressSeed=36200582 -XX:CompileCommand=quiet

Suggestion:

 * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions -XX:StressSeed=36200582 -XX:CompileCommand=quiet

test/hotspot/jtreg/compiler/loopstripmining/TestMismatchedMemoryPhis.java line 31:

> 29:  *                   -XX:CompileCommand=compileonly,*TestMismatchedMemoryPhis*::mainTest -XX:-TieredCompilation
> 30:  *                   -Xcomp -XX:+StressIGVN -XX:+StressLoopPeeling -XX:PerMethodTrapLimit=0 TestMismatchedMemoryPhis
> 31:  * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:CompileCommand=quiet

Suggestion:

 * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions -XX:CompileCommand=quiet

-------------

PR Review: https://git.openjdk.org/jdk/pull/28677#pullrequestreview-3558546288
PR Review Comment: https://git.openjdk.org/jdk/pull/28677#discussion_r2603519906
PR Review Comment: https://git.openjdk.org/jdk/pull/28677#discussion_r2603520959