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Rollup merge of #124712 - Enselic:deprecate-inline-threshold, r=pnkfelix
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Deprecate no-op codegen option `-Cinline-threshold=...`

This deprecates `-Cinline-threshold` since using it has no effect. This has been the case since the new LLVM pass manager started being used, more than 2 years ago.

Recommend using `-Cllvm-args=--inline-threshold=...` instead.

Closes #89742 which is E-help-wanted.
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compiler-errors authored Jun 24, 2024
2 parents 00e5f58 + f5f067b commit faa28be
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Showing 8 changed files with 17 additions and 22 deletions.
3 changes: 0 additions & 3 deletions compiler/rustc_codegen_llvm/src/back/write.rs
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Expand Up @@ -564,9 +564,6 @@ pub(crate) unsafe fn llvm_optimize(

let llvm_plugins = config.llvm_plugins.join(",");

// FIXME: NewPM doesn't provide a facility to pass custom InlineParams.
// We would have to add upstream support for this first, before we can support
// config.inline_threshold and our more aggressive default thresholds.
let result = llvm::LLVMRustOptimize(
module.module_llvm.llmod(),
&*module.module_llvm.tm,
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2 changes: 0 additions & 2 deletions compiler/rustc_codegen_ssa/src/back/write.rs
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Expand Up @@ -120,7 +120,6 @@ pub struct ModuleConfig {
pub vectorize_loop: bool,
pub vectorize_slp: bool,
pub merge_functions: bool,
pub inline_threshold: Option<u32>,
pub emit_lifetime_markers: bool,
pub llvm_plugins: Vec<String>,
}
Expand Down Expand Up @@ -280,7 +279,6 @@ impl ModuleConfig {
}
},

inline_threshold: sess.opts.cg.inline_threshold,
emit_lifetime_markers: sess.emit_lifetime_markers(),
llvm_plugins: if_regular!(sess.opts.unstable_opts.llvm_plugins.clone(), vec![]),
}
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6 changes: 5 additions & 1 deletion compiler/rustc_driver_impl/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1133,7 +1133,11 @@ pub fn describe_flag_categories(early_dcx: &EarlyDiagCtxt, matches: &Matches) ->
}

if cg_flags.iter().any(|x| *x == "no-stack-check") {
early_dcx.early_warn("the --no-stack-check flag is deprecated and does nothing");
early_dcx.early_warn("the `-Cno-stack-check` flag is deprecated and does nothing");
}

if cg_flags.iter().any(|x| x.starts_with("inline-threshold")) {
early_dcx.early_warn("the `-Cinline-threshold` flag is deprecated and does nothing (consider using `-Cllvm-args=--inline-threshold=...`)");
}

if cg_flags.iter().any(|x| *x == "passes=list") {
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3 changes: 2 additions & 1 deletion compiler/rustc_session/src/options.rs
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Expand Up @@ -1499,7 +1499,8 @@ options! {
incremental: Option<String> = (None, parse_opt_string, [UNTRACKED],
"enable incremental compilation"),
inline_threshold: Option<u32> = (None, parse_opt_number, [TRACKED],
"set the threshold for inlining a function"),
"this option is deprecated and does nothing \
(consider using `-Cllvm-args=--inline-threshold=...`)"),
#[rustc_lint_opt_deny_field_access("use `Session::instrument_coverage` instead of this field")]
instrument_coverage: InstrumentCoverage = (InstrumentCoverage::No, parse_instrument_coverage, [TRACKED],
"instrument the generated code to support LLVM source-based code coverage reports \
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17 changes: 3 additions & 14 deletions src/doc/rustc/src/codegen-options/index.md
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Expand Up @@ -184,20 +184,9 @@ incremental files will be stored.

## inline-threshold

This option lets you set the default threshold for inlining a function. It
takes an unsigned integer as a value. Inlining is based on a cost model, where
a higher threshold will allow more inlining.

The default depends on the [opt-level](#opt-level):

| opt-level | Threshold |
|-----------|-----------|
| 0 | N/A, only inlines always-inline functions |
| 1 | N/A, only inlines always-inline functions and LLVM lifetime intrinsics |
| 2 | 225 |
| 3 | 275 |
| s | 75 |
| z | 25 |
This option is deprecated and does nothing.

Consider using `-Cllvm-args=--inline-threshold=...`.

## instrument-coverage

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2 changes: 1 addition & 1 deletion tests/ui/codegen/issue-82833-slice-miscompile.rs
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
//@ run-pass
//@ compile-flags: -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Copt-level=0 -Cdebuginfo=2
//@ compile-flags: -Ccodegen-units=1 -Cllvm-args=--inline-threshold=0 -Clink-dead-code -Copt-level=0 -Cdebuginfo=2

// Make sure LLVM does not miscompile this.

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4 changes: 4 additions & 0 deletions tests/ui/deprecation/deprecated_inline_threshold.rs
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@@ -0,0 +1,4 @@
//@ check-pass
//@ compile-flags: -Cinline-threshold=666

fn main() {}
2 changes: 2 additions & 0 deletions tests/ui/deprecation/deprecated_inline_threshold.stderr
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@@ -0,0 +1,2 @@
warning: the `-Cinline-threshold` flag is deprecated and does nothing (consider using `-Cllvm-args=--inline-threshold=...`)

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