Auto merge of #37994 - upsuper:msvc-link-opt, r=alexcrichton
Don't apply msvc link opts for non-opt build `/OPT:REF,ICF` sometimes takes lots of time. It makes no sense to apply them when doing debug build. MSVC's linker by default disables these optimizations when `/DEBUG` is specified, unless they are explicitly passed.
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commit
1842efbae4
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@ -321,7 +321,16 @@ impl<'a> Linker for MsvcLinker<'a> {
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}
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fn gc_sections(&mut self, _keep_metadata: bool) {
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self.cmd.arg("/OPT:REF,ICF");
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// MSVC's ICF (Identical COMDAT Folding) link optimization is
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// slow for Rust and thus we disable it by default when not in
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// optimization build.
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if self.sess.opts.optimize != config::OptLevel::No {
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self.cmd.arg("/OPT:REF,ICF");
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} else {
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// It is necessary to specify NOICF here, because /OPT:REF
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// implies ICF by default.
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self.cmd.arg("/OPT:REF,NOICF");
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}
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}
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fn link_dylib(&mut self, lib: &str) {
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@ -25,7 +25,7 @@ all:
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# Should not link dead code...
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$(RUSTC) -Z print-link-args dummy.rs 2>&1 | \
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grep -e '--gc-sections' -e '-dead_strip' -e '/OPT:REF,ICF'
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grep -e '--gc-sections' -e '-dead_strip' -e '/OPT:REF'
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# ... unless you specifically ask to keep it
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$(RUSTC) -Z print-link-args -C link-dead-code dummy.rs 2>&1 | \
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(! grep -e '--gc-sections' -e '-dead_strip' -e '/OPT:REF,ICF')
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(! grep -e '--gc-sections' -e '-dead_strip' -e '/OPT:REF')
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