libunwind changes needed to run code in sgx environment via rust-sgx. - #63
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Code is guarded via defines to enable only if 'RUST_SGX' is present. Main logic is in libunwind/src/AddressSpace.hpp We use 6 symbols to figure out where eh_frame / eh_frame_hdr is at runtime when loaded in an SGX enclave. (EH symbols + IMAGE base) These are set by 'fortanix-sgx-tools'. As notes: - Target above at the moment uses a pre-compiled libunwind.a from forked repo. - Goal of these changes is to use official llvm with patch. - Changes in rust-lang to use this are planned if/when this is accepted. - Ticket: fortanix/rust-sgx#174 - Original ported changes: llvm/llvm-project@release/5.x...fortanix:release/5.x
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63: Kill some dead code in the control point pass. r=ltratt a=vext01 Co-authored-by: Edd Barrett <vext01@gmail.com>
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…SHL (llvm#207628) `select(icmp ult(amt, EltSize), shl(x, amt), 0)`, where EltSize is the {8, 16, 32, 64} lane size, is the usual way to guard a variable vector shift against shl poison. On AArch64 the guard is unnecessary because USHL already returns zero once the shift amount reaches the lane size. For v4i32: Before: ``` movi v2.4s, rust-lang#63 movi v3.4s, rust-lang#32 and v1.16b, v1.16b, v2.16b ushl v0.4s, v0.4s, v1.4s cmhi v1.4s, v3.4s, v1.4s and v0.16b, v1.16b, v0.16b ``` After: ``` movi v2.4s, rust-lang#63 and v1.16b, v1.16b, v2.16b ushl v0.4s, v0.4s, v1.4s ``` USHL reads each lane's shift amount as a signed value from its low byte so amounts above 127 would be misread. The fold applies directly when known bits can prove the amounts are at most 127 and otherwise the amounts are clamped to EltSize with umin first, which is still one instruction cheaper than the select. NEON has no umin for 64-bit lanes so unbounded v2i64 amounts use the SVE umin when available and otherwise keep the select. lshr gets the same fold since it already lowers to ushl with a negated amount. This is the AArch64 counterpart of llvm#86922, which added the same folds for AVX2's variable shifts. This does the select(shift) half; the shift(select) form will be a follow-up. Closes llvm#200698.
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Updated branch in response to: #57 (comment)
Please advise on process as this is the first PR against rust-lang's llvm and I tried to follow instructions as close as possible..
Ticket: fortanix/rust-sgx#174
Description: libunwind changes needed to run code in sgx environment via rust-sgx.
Target that uses this in rust: x86_64-fortanix-unknown-sgx.
Rust-lang PR depends on this - plan is to raise it if this PR is accepted.
Without this change, rust std for this toolchain is forced to use a precompiled library loaded via environment variable.
Code is guarded via defines to enable only if 'RUST_SGX' is present.
Main logic is in libunwind/src/AddressSpace.hpp
We use 6 symbols to figure out where eh_frame / eh_frame_hdr is at runtime when loaded in an SGX enclave. (EH symbols + IMAGE base)
These are set when elf is converged to sgx format by 'fortanix-sgx-tools'.
Original ported changes: llvm/llvm-project@release/5.x...fortanix:release/5.x