Use new LLVM pass manager

src/llvm/mod.rs

@@ -18,8 +18,7 @@ use llvm_sys::prelude::*;
 use llvm_sys::support::LLVMParseCommandLineOptions;
 use llvm_sys::target::*;
 use llvm_sys::target_machine::*;
-use llvm_sys::transforms::ipo::*;
-use llvm_sys::transforms::pass_manager_builder::*;
+use llvm_sys::transforms::pass_builder::*;
 use llvm_sys::LLVMAttributeFunctionIndex;
 use llvm_sys::{LLVMLinkage, LLVMVisibility};
 use log::*;
@@ -176,65 +175,48 @@ pub unsafe fn optimize(
         LLVMSetModuleInlineAsm2(module, ptr::null_mut(), 0);
     }
 
-    let mpm = LLVMCreatePassManager();
-    let fpm = LLVMCreateFunctionPassManagerForModule(module);
-
-    LLVMAddAnalysisPasses(tm, mpm);
-    LLVMAddAnalysisPasses(tm, fpm);
-
-    // even with -O0 and without LTO we still want to avoid linking in unused code from core etc
-    LLVMAddGlobalDCEPass(mpm);
-
-    let pmb = LLVMPassManagerBuilderCreate();
-
-    use OptLevel::*;
-    let (inline_threshold, opt) = match opt_level {
-        No | SizeMin => (0, 1), // Pretty much nothing compiles with -O0 s∫o make it an alias for -O1
-        Less => (25, 1),
-        Default => (225, 2),
-        Aggressive => (275, 3),
-        Size => (25, 0),
-    };
-    LLVMPassManagerBuilderSetOptLevel(pmb, opt);
-    LLVMPassManagerBuilderSetSizeLevel(
-        pmb,
-        match opt_level {
-            Size => 1,
-            SizeMin => 2,
-            _ => 0,
-        },
-    );
-    LLVMPassManagerBuilderUseInlinerWithThreshold(pmb, inline_threshold);
-
-    // populate the pass managers
-    LLVMPassManagerBuilderPopulateFunctionPassManager(pmb, fpm);
-    LLVMPassManagerBuilderPopulateModulePassManager(pmb, mpm);
-
     for sym in module.globals_iter() {
         internalize(sym, symbol_name(sym), export_symbols);
     }
     for sym in module.global_aliases_iter() {
         internalize(sym, symbol_name(sym), export_symbols);
     }
 
-    debug!("running function passes");
-    LLVMInitializeFunctionPassManager(fpm);
     for function in module.functions_iter() {
         let name = symbol_name(function);
         if !name.starts_with("llvm.") {
             if ignore_inline_never {
                 remove_attribute(function, "noinline");
             }
             internalize(function, name, export_symbols);
-            if LLVMIsDeclaration(function) == 0 {
-                LLVMRunFunctionPassManager(fpm, function);
-            }
         }
     }
-    LLVMFinalizeFunctionPassManager(fpm);
 
-    debug!("running module passes");
-    LLVMRunPassManager(mpm, module);
+    let options = LLVMCreatePassBuilderOptions();
+
+    let passes = [
+        // NB: "default<_>" must be the first pass in the list, otherwise it will be ignored.
+        match opt_level {
+            // Pretty much nothing compiles with -O0 so make it an alias for -O1.
+            OptLevel::No | OptLevel::Less => "default<O1>",
+            OptLevel::Default => "default<O2>",
+            OptLevel::Aggressive => "default<O3>",
+            OptLevel::Size => "default<Os>",
+            OptLevel::SizeMin => "default<Oz>",
+        },
+        // NB: This seems to be included in most default pipelines, but not obviously all of them.
+        // See
+        // https://github.com/llvm/llvm-project/blob/bbe2887f/llvm/lib/Passes/PassBuilderPipelines.cpp#L2011-L2012
+        // for a case which includes DCE only conditionally. Better safe than sorry; include it always.
+        "dce",
+    ];
+
+    let passes = passes.join(",");
+    debug!("running passes: {passes}");
+    let passes = CString::new(passes).unwrap();
+    LLVMRunPasses(module, passes.as_ptr(), tm, options);
+
+    LLVMDisposePassBuilderOptions(options);
 
     // Some debug info generated by rustc seems to trigger a segfault in the
     // BTF code in llvm, so strip it until that is fixed