From 598acffa609f1179d13f6d6004fec0b4bcf20b50 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Fri, 14 Jul 2023 11:11:59 +0000
Subject: [PATCH 1/3] make opt diagnostic kinds printable

---
 compiler/rustc_codegen_llvm/src/llvm/diagnostic.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/rustc_codegen_llvm/src/llvm/diagnostic.rs b/compiler/rustc_codegen_llvm/src/llvm/diagnostic.rs
index 45de284d22a..06e846a2b45 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/diagnostic.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/diagnostic.rs
@@ -9,7 +9,7 @@
 use super::{DiagnosticInfo, SMDiagnostic};
 use rustc_span::InnerSpan;
 
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 pub enum OptimizationDiagnosticKind {
     OptimizationRemark,
     OptimizationMissed,

From 77d01103a3b6d4cd0c1713d2f17233c620c7747d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Fri, 14 Jul 2023 14:26:15 +0000
Subject: [PATCH 2/3] filter LLVM diagnostics before crossing the rust bridge

this will eliminate many short-lived allocations (e.g. 20% of the memory used
building cargo) when unpacking the diagnostic and converting its various
C++ strings into rust strings, just to be filtered out most of the time.
---
 compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index ab5fa961b95..cbc18c0f6c6 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -1905,12 +1905,19 @@ extern "C" void LLVMRustContextConfigureDiagnosticHandler(
           LlvmRemarkStreamer(std::move(LlvmRemarkStreamer)) {}
 
     virtual bool handleDiagnostics(const DiagnosticInfo &DI) override {
-      if (this->LlvmRemarkStreamer) {
-        if (auto *OptDiagBase = dyn_cast<DiagnosticInfoOptimizationBase>(&DI)) {
-          if (OptDiagBase->isEnabled()) {
+      // If this diagnostic is one of the optimization remark kinds, we can check if it's enabled
+      // before emitting it. This can avoid many short-lived allocations when unpacking the
+      // diagnostic and converting its various C++ strings into rust strings.
+      // FIXME: some diagnostic infos still allocate before we get here, and avoiding that would be
+      // good in the future. That will require changing a few call sites in LLVM.
+      if (auto *OptDiagBase = dyn_cast<DiagnosticInfoOptimizationBase>(&DI)) {
+        if (OptDiagBase->isEnabled()) {
+          if (this->LlvmRemarkStreamer) {
             this->LlvmRemarkStreamer->emit(*OptDiagBase);
             return true;
           }
+        } else {
+          return true;
         }
       }
       if (DiagnosticHandlerCallback) {

From ca5a383fb6b16679b31029ab5da8438b5ef03e1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Fri, 14 Jul 2023 16:09:04 +0000
Subject: [PATCH 3/3] remove remark filtering on the rust side

now that remarks are filtered before cg_llvm's diagnostic handler callback
is called, we don't need to do the filtering post c++-to-rust conversion
of the diagnostic.
---
 compiler/rustc_codegen_llvm/src/back/write.rs | 39 ++++++++-----------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 0f5e975445f..46874b50990 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -382,29 +382,22 @@ fn report_inline_asm(
         }
 
         llvm::diagnostic::Optimization(opt) => {
-            let enabled = match cgcx.remark {
-                Passes::All => true,
-                Passes::Some(ref v) => v.iter().any(|s| *s == opt.pass_name),
-            };
-
-            if enabled {
-                diag_handler.emit_note(FromLlvmOptimizationDiag {
-                    filename: &opt.filename,
-                    line: opt.line,
-                    column: opt.column,
-                    pass_name: &opt.pass_name,
-                    kind: match opt.kind {
-                        OptimizationDiagnosticKind::OptimizationRemark => "success",
-                        OptimizationDiagnosticKind::OptimizationMissed
-                        | OptimizationDiagnosticKind::OptimizationFailure => "missed",
-                        OptimizationDiagnosticKind::OptimizationAnalysis
-                        | OptimizationDiagnosticKind::OptimizationAnalysisFPCommute
-                        | OptimizationDiagnosticKind::OptimizationAnalysisAliasing => "analysis",
-                        OptimizationDiagnosticKind::OptimizationRemarkOther => "other",
-                    },
-                    message: &opt.message,
-                });
-            }
+            diag_handler.emit_note(FromLlvmOptimizationDiag {
+                filename: &opt.filename,
+                line: opt.line,
+                column: opt.column,
+                pass_name: &opt.pass_name,
+                kind: match opt.kind {
+                    OptimizationDiagnosticKind::OptimizationRemark => "success",
+                    OptimizationDiagnosticKind::OptimizationMissed
+                    | OptimizationDiagnosticKind::OptimizationFailure => "missed",
+                    OptimizationDiagnosticKind::OptimizationAnalysis
+                    | OptimizationDiagnosticKind::OptimizationAnalysisFPCommute
+                    | OptimizationDiagnosticKind::OptimizationAnalysisAliasing => "analysis",
+                    OptimizationDiagnosticKind::OptimizationRemarkOther => "other",
+                },
+                message: &opt.message,
+            });
         }
         llvm::diagnostic::PGO(diagnostic_ref) | llvm::diagnostic::Linker(diagnostic_ref) => {
             let message = llvm::build_string(|s| {