enable parallel codegen by default #18213
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| Subproject commit ec1fdb3b9d3b1fb9e1dae97a65dd3a13db9bfb23 | |||
| Subproject commit c9b823739d1357a058e7437c00bec6d2d0b00ed6 | |||
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Looks like this accidentally reverts the submodule?
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Awesome. r=me modulo fixing the (presumed accidental) change to llvm. |
Enable parallel codegen (2 units) by default when --opt-level is 0 or 1. This gives a minor speedup on large crates (~10%), with only a tiny slowdown (~2%) for small ones (which usually build in under a second regardless). The current default (no parallelization) is used when the user requests optimization (--opt-level 2 or 3), and when the user has enabled LTO (which is incompatible with parallel codegen). This commit also changes the rust build system to use parallel codegen when appropriate. This means codegen-units=4 for stage0 always, and also for stage1 and stage2 when configured with --disable-optimize. (Other settings use codegen-units=1 for stage1 and stage2, to get maximum performance for release binaries.) The build system also sets codegen-units=1 for compiletest tests (compiletest does its own parallelization) and uses the same setting as stage2 for crate tests.
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Enable parallel codegen (2 units) by default when --opt-level is 0 or 1. This gives a minor speedup on large crates (~10%), with only a tiny slowdown (~2%) for small ones (which usually build in under a second regardless). The current default (no parallelization) is used when the user requests optimization (--opt-level 2 or 3), and when the user has enabled LTO (which is incompatible with parallel codegen). This commit also changes the rust build system to use parallel codegen when appropriate. This means codegen-units=4 for stage0 always, and also for stage1 and stage2 when configured with --disable-optimize. (Other settings use codegen-units=1 for stage1 and stage2, to get maximum performance for release binaries.) The build system also sets codegen-units=1 for compiletest tests (compiletest does its own parallelization) and uses the same setting as stage2 for crate tests. r? @aturon
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Enable parallel codegen (2 units) by default when --opt-level is 0 or 1. This
gives a minor speedup on large crates (~10%), with only a tiny slowdown (~2%)
for small ones (which usually build in under a second regardless). The current
default (no parallelization) is used when the user requests optimization
(--opt-level 2 or 3), and when the user has enabled LTO (which is incompatible
with parallel codegen).
This commit also changes the rust build system to use parallel codegen
when appropriate. This means codegen-units=4 for stage0 always, and
also for stage1 and stage2 when configured with --disable-optimize.
(Other settings use codegen-units=1 for stage1 and stage2, to get
maximum performance for release binaries.) The build system also sets
codegen-units=1 for compiletest tests (compiletest does its own
parallelization) and uses the same setting as stage2 for crate tests.
r? @aturon