[AsmPrinter] Fix crash when remarks section is unsupported (#144724)

Emit a warning and bail out instead of segfault-ing when the current
object file format does not have support for emitting a remarks section.

Author: tobias-stadler

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -2383,6 +2383,15 @@ void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
   if (!RS.needsSection())
     return;
 
+  MCSection *RemarksSection =
+      OutContext.getObjectFileInfo()->getRemarksSection();
+  if (!RemarksSection) {
+    OutContext.reportWarning(SMLoc(), "Current object file format does not "
+                                      "support remarks sections. Use the yaml "
+                                      "remark format instead.");
+    return;
+  }
+
   remarks::RemarkSerializer &RemarkSerializer = RS.getSerializer();
 
   std::optional<SmallString<128>> Filename;
@@ -2400,10 +2409,7 @@ void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
   MetaSerializer->emit();
 
   // Switch to the remarks section.
-  MCSection *RemarksSection =
-      OutContext.getObjectFileInfo()->getRemarksSection();
   OutStreamer->switchSection(RemarksSection);
-
   OutStreamer->emitBinaryData(Buf);
 }
 

llvm/test/CodeGen/X86/remarks-section.ll

@@ -5,6 +5,8 @@
 ; RUN: llc < %s -mtriple=x86_64-darwin --pass-remarks-format=bitstream -remarks-section=false -pass-remarks-output=%/t.yaml | FileCheck --check-prefix=CHECK-DARWIN-OVERRIDE-BITSTREAM %s
 ; RUN: llc < %s -mtriple=x86_64-darwin --pass-remarks-format=yaml -remarks-section=true -pass-remarks-output=%/t.yaml | FileCheck --check-prefix=CHECK-DARWIN-OVERRIDE-YAML %s
 
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu --pass-remarks-format=bitstream -pass-remarks-output=%/t.yaml 2>&1 | FileCheck --check-prefix=CHECK-LINUX-DEFAULT-BITSTREAM %s
+
 ; CHECK-DARWIN: .section __LLVM,__remarks,regular,debug
 ; CHECK-DARWIN-NEXT: .byte
 
@@ -22,3 +24,6 @@
 define void @func1() {
   ret void
 }
+
+; Currently no ELF support for bitstream remarks
+; CHECK-LINUX-DEFAULT-BITSTREAM: warning: Current object file format does not support remarks sections. Use the yaml remark format instead.