Emit LLVM optimization remarks when enabled with -Cremark

The default diagnostic handler considers all remarks to be disabled by
default unless configured otherwise through LLVM internal flags:
`-pass-remarks`, `-pass-remarks-missed`, and `-pass-remarks-analysis`.
This behaviour makes `-Cremark` ineffective on its own.

Fix this by configuring a custom diagnostic handler that enables
optimization remarks based on the value of `-Cremark` option. With
`-Cremark=all` enabling all remarks.

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -259,6 +259,7 @@ pub(crate) fn save_temp_bitcode(
 pub struct DiagnosticHandlers<'a> {
     data: *mut (&'a CodegenContext<LlvmCodegenBackend>, &'a Handler),
     llcx: &'a llvm::Context,
+    old_handler: Option<&'a llvm::DiagnosticHandler>,
 }
 
 impl<'a> DiagnosticHandlers<'a> {
@@ -267,12 +268,35 @@ impl<'a> DiagnosticHandlers<'a> {
         handler: &'a Handler,
         llcx: &'a llvm::Context,
     ) -> Self {
+        let remark_passes_all: bool;
+        let remark_passes: Vec<CString>;
+        match &cgcx.remark {
+            Passes::All => {
+                remark_passes_all = true;
+                remark_passes = Vec::new();
+            }
+            Passes::Some(passes) => {
+                remark_passes_all = false;
+                remark_passes =
+                    passes.iter().map(|name| CString::new(name.as_str()).unwrap()).collect();
+            }
+        };
+        let remark_passes: Vec<*const c_char> =
+            remark_passes.iter().map(|name: &CString| name.as_ptr()).collect();
         let data = Box::into_raw(Box::new((cgcx, handler)));
         unsafe {
+            let old_handler = llvm::LLVMRustContextGetDiagnosticHandler(llcx);
+            llvm::LLVMRustContextConfigureDiagnosticHandler(
+                llcx,
+                diagnostic_handler,
+                data.cast(),
+                remark_passes_all,
+                remark_passes.as_ptr(),
+                remark_passes.len(),
+            );
             llvm::LLVMRustSetInlineAsmDiagnosticHandler(llcx, inline_asm_handler, data.cast());
-            llvm::LLVMContextSetDiagnosticHandler(llcx, diagnostic_handler, data.cast());
+            DiagnosticHandlers { data, llcx, old_handler }
         }
-        DiagnosticHandlers { data, llcx }
     }
 }
 
@@ -281,7 +305,7 @@ impl<'a> Drop for DiagnosticHandlers<'a> {
         use std::ptr::null_mut;
         unsafe {
             llvm::LLVMRustSetInlineAsmDiagnosticHandler(self.llcx, inline_asm_handler, null_mut());
-            llvm::LLVMContextSetDiagnosticHandler(self.llcx, diagnostic_handler, null_mut());
+            llvm::LLVMRustContextSetDiagnosticHandler(self.llcx, self.old_handler);
             drop(Box::from_raw(self.data));
         }
     }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -672,8 +672,12 @@ pub struct OperandBundleDef<'a>(InvariantOpaque<'a>);
 #[repr(C)]
 pub struct Linker<'a>(InvariantOpaque<'a>);
 
-pub type DiagnosticHandler = unsafe extern "C" fn(&DiagnosticInfo, *mut c_void);
-pub type InlineAsmDiagHandler = unsafe extern "C" fn(&SMDiagnostic, *const c_void, c_uint);
+extern "C" {
+    pub type DiagnosticHandler;
+}
+
+pub type DiagnosticHandlerTy = unsafe extern "C" fn(&DiagnosticInfo, *mut c_void);
+pub type InlineAsmDiagHandlerTy = unsafe extern "C" fn(&SMDiagnostic, *const c_void, c_uint);
 
 pub mod coverageinfo {
     use super::coverage_map;
@@ -2286,12 +2290,6 @@ extern "C" {
     #[allow(improper_ctypes)]
     pub fn LLVMRustWriteTwineToString(T: &Twine, s: &RustString);
 
-    pub fn LLVMContextSetDiagnosticHandler(
-        C: &Context,
-        Handler: DiagnosticHandler,
-        DiagnosticContext: *mut c_void,
-    );
-
     #[allow(improper_ctypes)]
     pub fn LLVMRustUnpackOptimizationDiagnostic(
         DI: &'a DiagnosticInfo,
@@ -2321,7 +2319,7 @@ extern "C" {
 
     pub fn LLVMRustSetInlineAsmDiagnosticHandler(
         C: &Context,
-        H: InlineAsmDiagHandler,
+        H: InlineAsmDiagHandlerTy,
         CX: *mut c_void,
     );
 
@@ -2436,4 +2434,19 @@ extern "C" {
         mod_id: *const c_char,
         data: &ThinLTOData,
     );
+
+    pub fn LLVMRustContextGetDiagnosticHandler(Context: &Context) -> Option<&DiagnosticHandler>;
+    pub fn LLVMRustContextSetDiagnosticHandler(
+        context: &Context,
+        diagnostic_handler: Option<&DiagnosticHandler>,
+    );
+    pub fn LLVMRustContextConfigureDiagnosticHandler(
+        context: &Context,
+        diagnostic_handler_callback: DiagnosticHandlerTy,
+        diagnostic_handler_context: *mut c_void,
+        remark_all_passes: bool,
+        remark_passes: *const *const c_char,
+        remark_passes_len: usize,
+    );
+
 }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1,5 +1,6 @@
 #include "LLVMWrapper.h"
 #include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/DiagnosticHandler.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/GlobalVariable.h"
@@ -1767,3 +1768,92 @@ extern "C" LLVMRustResult LLVMRustWriteImportLibrary(
     return LLVMRustResult::Success;
   }
 }
+
+// Transfers ownership of DiagnosticHandler unique_ptr to the caller.
+extern "C" DiagnosticHandler *
+LLVMRustContextGetDiagnosticHandler(LLVMContextRef C) {
+  std::unique_ptr<DiagnosticHandler> DH = unwrap(C)->getDiagnosticHandler();
+  return DH.release();
+}
+
+// Sets unique_ptr to object of DiagnosticHandler to provide custom diagnostic
+// handling. Ownership of the handler is moved to the LLVMContext.
+extern "C" void LLVMRustContextSetDiagnosticHandler(LLVMContextRef C,
+                                                    DiagnosticHandler *DH) {
+  unwrap(C)->setDiagnosticHandler(std::unique_ptr<DiagnosticHandler>(DH));
+}
+
+using LLVMDiagnosticHandlerTy = DiagnosticHandler::DiagnosticHandlerTy;
+
+// Configures a diagnostic handler that invokes provided callback when a
+// backend needs to emit a diagnostic.
+//
+// When RemarkAllPasses is true, remarks are enabled for all passes. Otherwise
+// the RemarkPasses array specifies individual passes for which remarks will be
+// enabled.
+extern "C" void LLVMRustContextConfigureDiagnosticHandler(
+    LLVMContextRef C, LLVMDiagnosticHandlerTy DiagnosticHandlerCallback,
+    void *DiagnosticHandlerContext, bool RemarkAllPasses,
+    const char * const * RemarkPasses, size_t RemarkPassesLen) {
+
+  class RustDiagnosticHandler final : public DiagnosticHandler {
+  public:
+    RustDiagnosticHandler(LLVMDiagnosticHandlerTy DiagnosticHandlerCallback,
+                          void *DiagnosticHandlerContext,
+                          bool RemarkAllPasses,
+                          std::vector<std::string> RemarkPasses)
+        : DiagnosticHandlerCallback(DiagnosticHandlerCallback),
+          DiagnosticHandlerContext(DiagnosticHandlerContext),
+          RemarkAllPasses(RemarkAllPasses),
+          RemarkPasses(RemarkPasses) {}
+
+    virtual bool handleDiagnostics(const DiagnosticInfo &DI) override {
+      if (DiagnosticHandlerCallback) {
+        DiagnosticHandlerCallback(DI, DiagnosticHandlerContext);
+        return true;
+      }
+      return false;
+    }
+
+    bool isAnalysisRemarkEnabled(StringRef PassName) const override {
+      return isRemarkEnabled(PassName);
+    }
+
+    bool isMissedOptRemarkEnabled(StringRef PassName) const override {
+      return isRemarkEnabled(PassName);
+    }
+
+    bool isPassedOptRemarkEnabled(StringRef PassName) const override {
+      return isRemarkEnabled(PassName);
+    }
+
+    bool isAnyRemarkEnabled() const override {
+      return RemarkAllPasses || !RemarkPasses.empty();
+    }
+
+  private:
+    bool isRemarkEnabled(StringRef PassName) const {
+      if (RemarkAllPasses)
+        return true;
+
+      for (auto &Pass : RemarkPasses)
+        if (Pass == PassName)
+          return true;
+
+      return false;
+    }
+
+    LLVMDiagnosticHandlerTy DiagnosticHandlerCallback = nullptr;
+    void *DiagnosticHandlerContext = nullptr;
+
+    bool RemarkAllPasses = false;
+    std::vector<std::string> RemarkPasses;
+  };
+
+  std::vector<std::string> Passes;
+  for (size_t I = 0; I != RemarkPassesLen; ++I)
+    Passes.push_back(RemarkPasses[I]);
+
+  unwrap(C)->setDiagnosticHandler(std::make_unique<RustDiagnosticHandler>(
+      DiagnosticHandlerCallback, DiagnosticHandlerContext, RemarkAllPasses, Passes));
+}

src/test/ui/optimization-remark.rs

@@ -0,0 +1,19 @@
+// build-pass
+// ignore-pass
+// no-system-llvm
+// revisions: all inline
+//          compile-flags: --crate-type=lib -Cdebuginfo=1 -Copt-level=2
+// [all]    compile-flags: -Cremark=all
+// [inline] compile-flags: -Cremark=inline
+// error-pattern: inline: f not inlined into g
+// dont-check-compiler-stderr
+
+#[no_mangle]
+#[inline(never)]
+pub fn f() {
+}
+
+#[no_mangle]
+pub fn g() {
+    f();
+}