Rollup merge of #152474 - sgasho:opt-bisect-limit-mir, r=saethlin

Implement opt-bisect-limit for MIR closes: rust-lang/rust#150910 Enable bisecting MIR optimization passes to enhance debuggability. discussions on zulip: https://rust-lang.zulipchat.com/#narrow/channel/182449-t-compiler.2Fhelp/topic/MIR.20dump.20the.20pass.20names/with/573219207 ### Check it works #### Sample code ```rust fn abs(num: isize) -> usize { if num < 0 { -num as usize } else { num as usize } } fn main() { println!("{}", abs(-10)); } ``` #### Output ```shell rustc +mir -Zmir-opt-bisect-limit=30 src/main.rs BISECT: running pass (1) CheckAlignment on main[89d5]::main BISECT: running pass (2) CheckNull on main[89d5]::main BISECT: running pass (3) CheckEnums on main[89d5]::main BISECT: running pass (4) LowerSliceLenCalls on main[89d5]::main BISECT: running pass (5) InstSimplify-before-inline on main[89d5]::main BISECT: running pass (6) ForceInline on main[89d5]::main BISECT: running pass (7) RemoveStorageMarkers on main[89d5]::main BISECT: running pass (8) RemoveZsts on main[89d5]::main BISECT: running pass (9) RemoveUnneededDrops on main[89d5]::main BISECT: running pass (10) UnreachableEnumBranching on main[89d5]::main BISECT: running pass (11) SimplifyCfg-after-unreachable-enum-branching on main[89d5]::main BISECT: running pass (12) InstSimplify-after-simplifycfg on main[89d5]::main BISECT: running pass (13) SimplifyConstCondition-after-inst-simplify on main[89d5]::main BISECT: running pass (14) SimplifyLocals-before-const-prop on main[89d5]::main BISECT: running pass (15) SimplifyLocals-after-value-numbering on main[89d5]::main BISECT: running pass (16) MatchBranchSimplification on main[89d5]::main BISECT: running pass (17) SingleUseConsts on main[89d5]::main BISECT: running pass (18) SimplifyConstCondition-after-const-prop on main[89d5]::main BISECT: running pass (19) SimplifyConstCondition-final on main[89d5]::main BISECT: running pass (20) RemoveNoopLandingPads on main[89d5]::main BISECT: running pass (21) SimplifyCfg-final on main[89d5]::main BISECT: running pass (22) CopyProp on main[89d5]::main BISECT: running pass (23) SimplifyLocals-final on main[89d5]::main BISECT: running pass (24) AddCallGuards on main[89d5]::main BISECT: running pass (25) PreCodegen on main[89d5]::main BISECT: running pass (26) CheckAlignment on main[89d5]::abs BISECT: running pass (27) CheckNull on main[89d5]::abs BISECT: running pass (28) CheckEnums on main[89d5]::abs BISECT: running pass (29) LowerSliceLenCalls on main[89d5]::abs BISECT: running pass (30) InstSimplify-before-inline on main[89d5]::abs BISECT: NOT running pass (31) ForceInline on main[89d5]::abs BISECT: NOT running pass (32) RemoveStorageMarkers on main[89d5]::abs BISECT: NOT running pass (33) RemoveZsts on main[89d5]::abs BISECT: NOT running pass (34) RemoveUnneededDrops on main[89d5]::abs BISECT: NOT running pass (35) UnreachableEnumBranching on main[89d5]::abs BISECT: NOT running pass (36) SimplifyCfg-after-unreachable-enum-branching on main[89d5]::abs BISECT: NOT running pass (37) InstSimplify-after-simplifycfg on main[89d5]::abs BISECT: NOT running pass (38) SimplifyConstCondition-after-inst-simplify on main[89d5]::abs BISECT: NOT running pass (39) SimplifyLocals-before-const-prop on main[89d5]::abs BISECT: NOT running pass (40) SimplifyLocals-after-value-numbering on main[89d5]::abs BISECT: NOT running pass (41) MatchBranchSimplification on main[89d5]::abs BISECT: NOT running pass (42) SingleUseConsts on main[89d5]::abs BISECT: NOT running pass (43) SimplifyConstCondition-after-const-prop on main[89d5]::abs BISECT: NOT running pass (44) SimplifyConstCondition-final on main[89d5]::abs BISECT: NOT running pass (45) RemoveNoopLandingPads on main[89d5]::abs BISECT: NOT running pass (46) SimplifyCfg-final on main[89d5]::abs BISECT: NOT running pass (47) CopyProp on main[89d5]::abs BISECT: NOT running pass (48) SimplifyLocals-final on main[89d5]::abs BISECT: NOT running pass (49) AddCallGuards on main[89d5]::abs BISECT: NOT running pass (50) PreCodegen on main[89d5]::abs ``` r? @saethlin
2026-02-18 17:29:46 +11:00 · 2026-02-18 17:29:46 +11:00 · 544462ad8b
commit 544462ad8b
parent ae196c772d 28c8d71544
5 changed files with 198 additions and 1 deletions
--- a/tests/run-make/mir-opt-bisect-limit/main.rs
+++ b/tests/run-make/mir-opt-bisect-limit/main.rs
@ -0,0 +1,11 @@
+#![crate_type = "lib"]
+#![no_std]
+
+#[inline(never)]
+pub fn callee(x: u64) -> u64 {
+    x.wrapping_mul(3).wrapping_add(7)
+}
+
+pub fn caller(a: u64, b: u64) -> u64 {
+    callee(a) + callee(b)
+}
--- a/tests/run-make/mir-opt-bisect-limit/rmake.rs
+++ b/tests/run-make/mir-opt-bisect-limit/rmake.rs
@ -0,0 +1,119 @@
+use std::path::Path;
+
+use run_make_support::{CompletedProcess, rfs, rustc};
+
+struct Case {
+    name: &'static str,
+    flags: &'static [&'static str],
+    expect_inline_dump: bool,
+    expect_running: ExpectedCount,
+    expect_not_running: ExpectedCount,
+}
+
+enum ExpectedCount {
+    Exactly(usize),
+    AtLeastOne,
+    Zero,
+}
+
+fn main() {
+    let cases = [
+        Case {
+            name: "limit0",
+            flags: &["-Zmir-opt-bisect-limit=0"],
+            expect_inline_dump: false,
+            expect_running: ExpectedCount::Exactly(0),
+            expect_not_running: ExpectedCount::AtLeastOne,
+        },
+        Case {
+            name: "limit1",
+            flags: &["-Zmir-opt-bisect-limit=1"],
+            expect_inline_dump: false,
+            expect_running: ExpectedCount::Exactly(1),
+            expect_not_running: ExpectedCount::AtLeastOne,
+        },
+        Case {
+            name: "huge_limit",
+            flags: &["-Zmir-opt-bisect-limit=1000000000"],
+            expect_inline_dump: true,
+            expect_running: ExpectedCount::AtLeastOne,
+            expect_not_running: ExpectedCount::Zero,
+        },
+        Case {
+            name: "limit0_with_force_enable_inline",
+            flags: &["-Zmir-opt-bisect-limit=0", "-Zmir-enable-passes=+Inline"],
+            expect_inline_dump: false,
+            expect_running: ExpectedCount::Exactly(0),
+            expect_not_running: ExpectedCount::AtLeastOne,
+        },
+    ];
+
+    for case in cases {
+        let (inline_dumped, running_count, not_running_count, output) =
+            compile_case(case.name, case.flags);
+
+        assert_eq!(
+            inline_dumped, case.expect_inline_dump,
+            "{}: unexpected Inline dump presence",
+            case.name
+        );
+
+        assert_expected_count(
+            running_count,
+            case.expect_running,
+            &format!("{}: running count", case.name),
+        );
+        assert_expected_count(
+            not_running_count,
+            case.expect_not_running,
+            &format!("{}: NOT running count", case.name),
+        );
+    }
+}
+
+fn compile_case(dump_dir: &str, extra_flags: &[&str]) -> (bool, usize, usize, CompletedProcess) {
+    if Path::new(dump_dir).exists() {
+        rfs::remove_dir_all(dump_dir);
+    }
+    rfs::create_dir_all(dump_dir);
+
+    let mut cmd = rustc();
+    cmd.input("main.rs")
+        .arg("--emit=mir")
+        .arg("-Zmir-opt-level=2")
+        .arg("-Copt-level=2")
+        .arg("-Zthreads=1")
+        .arg("-Zdump-mir=Inline")
+        .arg(format!("-Zdump-mir-dir={dump_dir}"));
+
+    for &flag in extra_flags {
+        cmd.arg(flag);
+    }
+
+    let output = cmd.run();
+    let (running_count, not_running_count) = bisect_line_counts(&output);
+    (has_inline_dump_file(dump_dir), running_count, not_running_count, output)
+}
+
+fn assert_expected_count(actual: usize, expected: ExpectedCount, context: &str) {
+    match expected {
+        ExpectedCount::Exactly(n) => assert_eq!(actual, n, "{context}"),
+        ExpectedCount::AtLeastOne => assert!(actual > 0, "{context}"),
+        ExpectedCount::Zero => assert_eq!(actual, 0, "{context}"),
+    }
+}
+
+fn has_inline_dump_file(dir: &str) -> bool {
+    rfs::read_dir(dir)
+        .flatten()
+        .any(|entry| entry.file_name().to_string_lossy().contains(".Inline."))
+}
+
+fn bisect_line_counts(output: &CompletedProcess) -> (usize, usize) {
+    let stderr = output.stderr_utf8();
+    let running_count =
+        stderr.lines().filter(|line| line.starts_with("BISECT: running pass (")).count();
+    let not_running_count =
+        stderr.lines().filter(|line| line.starts_with("BISECT: NOT running pass (")).count();
+    (running_count, not_running_count)
+}