Fix transmutes between pointers in different address spaces (e.g. fn ptrs on AVR) #105578
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erikdesjardins
commented
Dec 11, 2022
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| // It doesn't matter precisely how this is codegenned (as a roundtrip through memory or an addrspacecast), | ||
| // as long as it doesn't cause a verifier error, e.g. by using `bitcast` (which was the case before). |
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This is codegenned as
%0 = addrspacecast ptr %x to ptr addrspace(1)I can add a check line instead if you'd prefer
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bjorn3
reviewed
Dec 13, 2022
| assert_eq!(src.layout.size, dst.layout.size); | ||
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| // NOTE(eddyb) the `from_immediate` and `to_immediate_scalar` | ||
| // conversions allow handling `bool`s the same as `u8`s. | ||
| let src = bx.from_immediate(src.immediate()); | ||
| let src_as_dst = bx.bitcast(src, bx.backend_type(dst.layout)); | ||
| // LLVM also doesn't like `bitcast`s between pointers in different address spaces. | ||
| let src_as_dst = if src_is_ptr { |
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What if the from type is a pointer and the to type is an integer? Does pointercast work for that?
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It doesn't, but that's not possible here due to src_is_ptr == dst_is_ptr above. I can change this line to src_is_ptr && dst_is_ptr if that would be clearer
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@bors r+ |
bors
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Dec 14, 2022
…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#105399 (Use more LFS functions.) - rust-lang#105578 (Fix transmutes between pointers in different address spaces (e.g. fn ptrs on AVR)) - rust-lang#105598 (explain mem::forget(env_lock) in fork/exec) - rust-lang#105624 (Fix unsoundness in bootstrap cache code) - rust-lang#105630 (Add a test for rust-lang#92481) - rust-lang#105684 (Improve rustdoc markdown variable naming) - rust-lang#105697 (Remove fee1-dead from reviewers) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Currently, this causes a verifier error (https://godbolt.org/z/YYohed4bj), since it uses
bitcast, which can't convert between address spaces.Uncovered due to #105545 (comment)
r? @bjorn3