[VM] Fix ref ownership in branch remaps - #24781
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Branch remaps selected MOVE using `isLastRealValueUse`, whose result accounts for uses across all successors. A use on one successor therefore prevented ownership transfer on another mutually exclusive successor, leaving an extra owning reference on the taken path. Use target-block liveness to select MOVE independently for each successor. If one occurrence of a repeated operand is coalesced with its destination, prevent the other remaps from using MOVE; otherwise a MOVE would clear the coalesced register. Add register allocation tests for both cases and an LLVM CPU end-to-end regression that executes both selector paths with indirect command buffers disabled. Fixes iree-org#24753 Co-authored-by: OpenAI <noreply@openai.com> Signed-off-by: zhangpan <98025960+zhangpan2001@users.noreply.github.com>
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need to take a closer look, at first glance this seems eerily close to #24841 |
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Branch remaps selected MOVE using
isLastRealValueUse, whose result accounts for uses across all successors. A use on one successor therefore prevented ownership transfer on another mutually exclusive successor, leaving an extra owning reference on the taken path.Use target-block liveness to select MOVE independently for each successor. If one occurrence of a repeated operand is coalesced with its destination, prevent the other remaps from using MOVE; otherwise a MOVE would clear the coalesced register.
Add register allocation tests for both cases and an LLVM CPU end-to-end regression that executes both selector paths with indirect command buffers disabled.
Fixes #24753