Add -Z llvm-opt-bisect-limit-cgu

Author: dianqk

.gitignore

@@ -1,3 +1,4 @@
+/*.log
 /const_prop_slice_pat_ice
 /*.txt
 # This file should only ignore things that are generated during a `x.py` build,

bisect.sh

@@ -0,0 +1,3 @@
+export RUSTFLAGS_NOT_BOOTSTRAP="-C llvm-args=-opt-bisect-limit=-1 -Z llvm-opt-bisect-limit-cgu=rustc_mir_build.63d28fcded2a05ed-cgu.007"
+./x build --stage 2 library --keep-stage 0 --keep-stage-std 1 2> build.log
+./build/host/stage2/bin/rustc ./tests/ui/consts/const_prop_slice_pat_ice.rs

compiler/rustc_codegen_llvm/src/lib.rs

@@ -415,6 +415,13 @@ impl ModuleLlvm {
     fn new(tcx: TyCtxt<'_>, mod_name: &str) -> Self {
         unsafe {
             let llcx = llvm::LLVMRustContextCreate(tcx.sess.fewer_names());
+            if let Some(ref only_cgu) = tcx.sess.opts.unstable_opts.llvm_opt_bisect_limit_cgu {
+                if mod_name != only_cgu {
+                    llvm::LLVMRustContextSetSetRunAllOptPassGate(llcx);
+                } else {
+                    eprintln!("opt-bisect-only: {}", only_cgu);
+                }
+            }
             let llmod_raw = context::create_module(tcx, llcx, mod_name) as *const _;
             ModuleLlvm { llmod_raw, llcx, tm: create_target_machine(tcx, mod_name) }
         }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2381,4 +2381,6 @@ extern "C" {
         callback: GetSymbolsCallback,
         error_callback: GetSymbolsErrorCallback,
     ) -> *mut c_void;
+
+    pub fn LLVMRustContextSetSetRunAllOptPassGate(context: &Context);
 }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -10,10 +10,12 @@
 #include "llvm/IR/IntrinsicsARM.h"
 #include "llvm/IR/LLVMRemarkStreamer.h"
 #include "llvm/IR/Mangler.h"
+#include "llvm/IR/OptBisect.h"
 #include "llvm/Remarks/RemarkStreamer.h"
 #include "llvm/Remarks/RemarkSerializer.h"
 #include "llvm/Remarks/RemarkFormat.h"
 #include "llvm/Support/ToolOutputFile.h"
+#include <llvm/IR/LLVMContext.h>
 #if LLVM_VERSION_GE(16, 0)
 #include "llvm/Support/ModRef.h"
 #endif
@@ -2060,3 +2062,19 @@ extern "C" bool LLVMRustLLVMHasZstdCompressionForDebugSymbols() {
   return false;
 #endif
 }
+
+struct RunAllOptPassGate : public OptPassGate {
+  bool shouldRunPass(const StringRef PassName, StringRef IRDescription) override {
+    return true;
+  }
+  bool isEnabled() const override { return true; }
+};
+
+static RunAllOptPassGate &getRunAllOptPassGate() {
+  static RunAllOptPassGate RunAllOptPassGate;
+  return RunAllOptPassGate;
+}
+
+extern "C" void LLVMRustContextSetSetRunAllOptPassGate(LLVMContextRef C) {
+  unwrap(C)->setOptPassGate(getRunAllOptPassGate());
+}

compiler/rustc_session/src/options.rs

@@ -1585,6 +1585,8 @@ options! {
         "link native libraries in the linker invocation (default: yes)"),
     link_only: bool = (false, parse_bool, [TRACKED],
         "link the `.rlink` file generated by `-Z no-link` (default: no)"),
+    llvm_opt_bisect_limit_cgu: Option<String> = (None, parse_opt_string, [UNTRACKED],
+        "apply -opt-bisect-limit to the specified cgu"),
     llvm_plugins: Vec<String> = (Vec::new(), parse_list, [TRACKED],
         "a list LLVM plugins to enable (space separated)"),
     llvm_time_trace: bool = (false, parse_bool, [UNTRACKED],

test.sh

@@ -1,2 +1,2 @@
-./x build --stage 2 library
+./x build --stage 2 library 2> build.log
 ./build/host/stage2/bin/rustc ./tests/ui/consts/const_prop_slice_pat_ice.rs