Backport Wasm 64-bit table fix to 19.x

[adambratschikaye]

In rustc, the wasm64-unknown-unknown target produces invalid Wasm modules due to an issue with 64-bit tables that was fixed in #107780. Would it be possible to backport that fix to the 19.x release branch so that rust can pick it up?

Here are steps to reproduce the issue with cargo/rustc:

❯ rustc +nightly --version
rustc 1.85.0-nightly (a224f3807 2024-12-09)

❯ cargo new --bin foo

❯ cd foo

❯ cargo +nightly build -Z build-std=std,panic_abort --target wasm64-unknown-unknown

❯ wasm-objdump -j Elem -x target/wasm64-unknown-unknown/debug/foo.wasm | head

foo.wasm:       file format wasm 0x1
module name: <foo-87b5668ca08bcff0.wasm>

Section Details:

Elem[1]:
 - segment[0] flags=0 table=0 count=91 - init i64=94235877441537
  - elem[94235877441537] = ref.func:3 <_ZN3foo4main17h3e4566f0ffb33d02E>
  - elem[94235877441538] = ref.func:5 <_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17ha696e16b756653ccE>

Here we can see the init expression for the table is reading uninitialized memory.

cc @sbc100 @alexcrichton @lwshang

[llvmbot]

@llvm/issue-subscribers-lld-wasm

Author: Adam Bratschi-Kaye (adambratschikaye)

In `rustc`, the `wasm64-unknown-unknown` target produces invalid Wasm modules due to an issue with 64-bit tables that was fixed in https://github.com//pull/107780. Would it be possible to backport that fix to the 19.x release branch so that rust can pick it up?

Here are steps to reproduce the issue with cargo/rustc:

❯ rustc +nightly --version
rustc 1.85.0-nightly (a224f3807 2024-12-09)

❯ cargo new --bin foo

❯ cd foo

❯ cargo +nightly build -Z build-std=std,panic_abort --target wasm64-unknown-unknown

❯ wasm-objdump -j Elem -x target/wasm64-unknown-unknown/debug/foo.wasm | head

foo.wasm:       file format wasm 0x1
module name: <foo-87b5668ca08bcff0.wasm>

Section Details:

Elem[1]:
 - segment[0] flags=0 table=0 count=91 - init i64=94235877441537
  - elem[94235877441537] = ref.func:3 <_ZN3foo4main17h3e4566f0ffb33d02E>
  - elem[94235877441538] = ref.func:5 <_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17ha696e16b756653ccE>

Here we can see the init expression for the table is reading uninitialized memory.

cc @sbc100 @alexcrichton @lwshang

[nikic]

/cherry-pick 5c8fd1e

[llvmbot]

/pull-request #119723