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Wasmtime+Cranelift: strip out some dead x86-32 code. (#5226)

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* Wasmtime+Cranelift: strip out some dead x86-32 code.

I was recently pointed to fastly/Viceroy#200 where it seems some folks
are trying to compile Wasmtime (via Viceroy) for Windows x86-32 and the
failures may not be loud enough. I've tried to reproduce this
cross-compiling to i686-pc-windows-gnu from Linux and hit build failures
(as expected) in several places.  Nevertheless, while trying to discern
what others may be attempting, I noticed some dead x86-32-specific code
in our repo, and figured it would be a good idea to clean this up.
Otherwise, it (i) sends some mixed messages -- "hey look, this codebase
does support x86-32" -- and (ii) keeps untested code around, which is
generally not great.

This PR removes x86-32-specific cases in traphandlers and unwind code,
and Cranelift's native feature detection. It adds helpful compile-error
messages in a few cases. If we ever support x86-32 (contributors
welcome! The big missing piece is Cranelift support; see #1980), these
compile errors and git history should be enough to recover any knowledge
we are now encoding in the source.

I left the x86-32 support in `wasmtime-fiber` alone because that seems
like a bit of a special case -- foundation library, separate from the
rest of Wasmtime, with specific care to provide a (presumably working)
full 32-bit version.

* Remove some extraneous compile_error!s, already covered by others.
This commit is contained in:
Chris Fallin
2022-11-08 15:03:17 -08:00
committed by GitHub
parent fd7b903f33
commit d59caf39b6
6 changed files with 12 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
crates/runtime/src/traphandlers/unix.rs
View File

@@ -47,16 +47,18 @@ pub unsafe fn platform_init() {
register(&mut PREV_SIGILL, libc::SIGILL);
// x86 and s390x use SIGFPE to report division by zero
if cfg!(target_arch = "x86") || cfg!(target_arch = "x86_64") || cfg!(target_arch = "s390x") {
if cfg!(target_arch = "x86_64") || cfg!(target_arch = "s390x") {
register(&mut PREV_SIGFPE, libc::SIGFPE);
}
// Sometimes we need to handle SIGBUS too:
// - On ARM, handle Unaligned Accesses.
// - On Darwin, guard page accesses are raised as SIGBUS.
if cfg!(target_arch = "arm") || cfg!(target_os = "macos") || cfg!(target_os = "freebsd") {
if cfg!(target_os = "macos") || cfg!(target_os = "freebsd") {
register(&mut PREV_SIGBUS, libc::SIGBUS);
}
// TODO(#1980): x86-32, if we support it, will also need a SIGFPE handler.
// TODO(#1173): ARM32, if we support it, will also need a SIGBUS handler.
}
unsafe extern "C" fn trap_handler(
@@ -172,12 +174,6 @@ unsafe fn get_pc_and_fp(cx: *mut libc::c_void, _signum: libc::c_int) -> (*const
cx.uc_mcontext.gregs[libc::REG_RIP as usize] as *const u8,
cx.uc_mcontext.gregs[libc::REG_RBP as usize] as usize
)
} else if #[cfg(all(target_os = "linux", target_arch = "x86"))] {
let cx = &*(cx as *const libc::ucontext_t);
(
cx.uc_mcontext.gregs[libc::REG_EIP as usize] as *const u8,
cx.uc_mcontext.gregs[libc::REG_EBP as usize] as usize,
)
} else if #[cfg(all(any(target_os = "linux", target_os = "android"), target_arch = "aarch64"))] {
let cx = &*(cx as *const libc::ucontext_t);
(
@@ -210,12 +206,6 @@ unsafe fn get_pc_and_fp(cx: *mut libc::c_void, _signum: libc::c_int) -> (*const
(*cx.uc_mcontext).__ss.__rip as *const u8,
(*cx.uc_mcontext).__ss.__rbp as usize,
)
} else if #[cfg(all(target_os = "macos", target_arch = "x86"))] {
let cx = &*(cx as *const libc::ucontext_t);
(
(*cx.uc_mcontext).__ss.__eip as *const u8,
(*cx.uc_mcontext).__ss.__ebp as usize,
)
} else if #[cfg(all(target_os = "macos", target_arch = "aarch64"))] {
let cx = &*(cx as *const libc::ucontext_t);
(