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Update asm blocks in workaround for framepointer clobber miscompilation #14

Merged
merged 3 commits into from
Jun 19, 2020
Merged

Update asm blocks in workaround for framepointer clobber miscompilation #14

merged 3 commits into from
Jun 19, 2020

Commits on Jun 17, 2020

  1. Move away from llvm_asm to new asm. 

    In my opinion, this makes the constraints a _lot_ easier to read, and
gets us things like noreturn. (Plus, it moves us off a deprecated
feature whose days are numbered.)

asm has opinions about trying to use r11. These opinions are misguided:
rust-lang/rust#73450

However, we respect them by manually moving values in and out of r11 in
the asm sequences.
    @cbiffle
    cbiffle committed Jun 17, 2020
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  2. userlib: centralize stub boilerplate in macro

    @cbiffle
    cbiffle committed Jun 17, 2020
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  3. userlib: alter handling of r7 in workaround 

    This completes the sequence of workarounds for:
rust-lang/rust#73450

r7 is the frame pointer. asm! cannot reason about clobbers of r7. It
tries to statically refuse it, but statically refuses r11 instead.

This avoids clobbering r7.
    @cbiffle
    cbiffle committed Jun 17, 2020
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