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Rollup merge of #85920 - luqmana:wasm-linker-tweaks, r=petrochenkov

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Tweak wasm_base target spec to indicate linker is not GNU and update linker inferring logic for wasm-ld.

Reported via [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/wasi.20linker.20unknown.20argument.3A.20--as-needed): we try passing `--as-needed` to the linker if it's GNU ld which `wasm-ld` is not. Usually this isn't an issue for wasm as we would use the WasmLd linker driver but because the linker in question (`wasm32-unknown-wasi-wasm-ld`) ended with `-ld` our linker inferring [logic](f64503eb55/compiler/rustc_codegen_ssa/src/back/link.rs (L957-L1040)) used the `GccLinker` implementations. (UPD: The linker inferring logic actually didn't apply in this case because the linker is actually invoked through gcc in the reported issue. But it's still worth updating the logic I think.)

This change then has 2 parts:
1. Update wasm_base target spec to indicate `linker_is_gnu: false` plus a few additions of `target.is_like_wasm` to handle flags `wasm-ld` does in fact support.
2. Improve the linker detection logic to properly determine the correct flavor of wasm linker we're using when we can.

We need to add the new `target.is_like_wasm` branches to handle the case where the "linker" used could be something like clang which would then under the hood call wasm-ld.
This commit is contained in:
Yuki Okushi 2021-06-06 19:11:18 +09:00 • committed by GitHub
commit 679a1d1ac1
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3 changed files with 8 additions and 3 deletions
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8
compiler/rustc_codegen_ssa/src/back/linker.rs
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@ -476,7 +476,9 @@ impl<'a> Linker for GccLinker<'a> {
// eliminate the metadata. If we're building an executable, however,
// --gc-sections drops the size of hello world from 1.8MB to 597K, a 67%
// reduction.
} else if self.sess.target.linker_is_gnu && !keep_metadata {
} else if (self.sess.target.linker_is_gnu || self.sess.target.is_like_wasm)
&& !keep_metadata
{
self.linker_arg("--gc-sections");
}
}
@ -484,13 +486,13 @@ impl<'a> Linker for GccLinker<'a> {
fn no_gc_sections(&mut self) {
if self.sess.target.is_like_osx {
self.linker_arg("-no_dead_strip");
} else if self.sess.target.linker_is_gnu {
} else if self.sess.target.linker_is_gnu || self.sess.target.is_like_wasm {
self.linker_arg("--no-gc-sections");
}
}
fn optimize(&mut self) {
if !self.sess.target.linker_is_gnu {
if !self.sess.target.linker_is_gnu && !self.sess.target.is_like_wasm {
return;
}