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internal: Sync from downstream #15494
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stabilize abi_thiscall Closes rust-lang/rust#42202, stabilizing the use of the "thiscall" ABI. FCP was substituted by a poll, and the poll has been accepted.
Similar to prior support added for the mips430, avr, and x86 targets this change implements the rough equivalent of clang's [`__attribute__((interrupt))`][clang-attr] for riscv targets, enabling e.g. ```rust static mut CNT: usize = 0; pub extern "riscv-interrupt-m" fn isr_m() { unsafe { CNT += 1; } } ``` to produce highly effective assembly like: ```asm pub extern "riscv-interrupt-m" fn isr_m() { 420003a0: 1141 addi sp,sp,-16 unsafe { CNT += 1; 420003a2: c62a sw a0,12(sp) 420003a4: c42e sw a1,8(sp) 420003a6: 3fc80537 lui a0,0x3fc80 420003aa: 63c52583 lw a1,1596(a0) # 3fc8063c <_ZN12esp_riscv_rt3CNT17hcec3e3a214887d53E.0> 420003ae: 0585 addi a1,a1,1 420003b0: 62b52e23 sw a1,1596(a0) } } 420003b4: 4532 lw a0,12(sp) 420003b6: 45a2 lw a1,8(sp) 420003b8: 0141 addi sp,sp,16 420003ba: 30200073 mret ``` (disassembly via `riscv64-unknown-elf-objdump -C -S --disassemble ./esp32c3-hal/target/riscv32imc-unknown-none-elf/release/examples/gpio_interrupt`) This outcome is superior to hand-coded interrupt routines which, lacking visibility into any non-assembly body of the interrupt handler, have to be very conservative and save the [entire CPU state to the stack frame][full-frame-save]. By instead asking LLVM to only save the registers that it uses, we defer the decision to the tool with the best context: it can more accurately account for the cost of spills if it knows that every additional register used is already at the cost of an implicit spill. At the LLVM level, this is apparently [implemented by] marking every register as "[callee-save]," matching the semantics of an interrupt handler nicely (it has to leave the CPU state just as it found it after its `{m|s}ret`). This approach is not suitable for every interrupt handler, as it makes no attempt to e.g. save the state in a user-accessible stack frame. For a full discussion of those challenges and tradeoffs, please refer to [the interrupt calling conventions RFC][rfc]. Inside rustc, this implementation differs from prior art because LLVM does not expose the "all-saved" function flavor as a calling convention directly, instead preferring to use an attribute that allows for differentiating between "machine-mode" and "superivsor-mode" interrupts. Finally, some effort has been made to guide those who may not yet be aware of the differences between machine-mode and supervisor-mode interrupts as to why no `riscv-interrupt` calling convention is exposed through rustc, and similarly for why `riscv-interrupt-u` makes no appearance (as it would complicate future LLVM upgrades). [clang-attr]: https://clang.llvm.org/docs/AttributeReference.html#interrupt-risc-v [full-frame-save]: https://github.com/esp-rs/esp-riscv-rt/blob/9281af2ecffe13e40992917316f36920c26acaf3/src/lib.rs#L440-L469 [implemented by]: https://github.com/llvm/llvm-project/blob/b7fb2a3fec7c187d58a6d338ab512d9173bca987/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp#L61-L67 [callee-save]: https://github.com/llvm/llvm-project/blob/973f1fe7a8591c7af148e573491ab68cc15b6ecf/llvm/lib/Target/RISCV/RISCVCallingConv.td#L30-L37 [rfc]: rust-lang/rfcs#3246
Not sure what's happening here. The two tests ( |
Huh, it's now working for me after upgrading to the latest nightly. |
@bors try |
💔 Test failed - checks-actions |
It looks like |
This is the one part thats annoying about upstream CI not running r-a tests, because this is the one integration test we do want to run ... |
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@bors r+ |
💥 Test timed out |
I can reproduce the hang on It's in const eval, looks like it's not a real hang, but each const takes about 4s. CC @HKalbasi |
@bors r+ |
☀️ Test successful - checks-actions |
@@ -86,6 +86,12 @@ jobs: | |||
- name: Test | |||
run: cargo test ${{ env.USE_SYSROOT_ABI }} -- --nocapture --quiet | |||
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- name: Switch to stable toolchain |
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@Veykril heads-up, just so you're aware of this change.
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