From 2ba5cda6f227b4aa5dfe91d32213efe603076162 Mon Sep 17 00:00:00 2001
From: Shubham Sandeep Rastogi <srastogi22@apple.com>
Date: Tue, 19 Aug 2025 18:48:41 -0700
Subject: [PATCH] Fix MCCAS issue with LEB and CVInline Fragments.

The 2100 branch took a snapshot of MC changes which reclassified LEB
and CVInline fragments as Encoded Fragments. We need to add support for
serializing both these fragment types in
MCDataFragmentMerger::emitMergedFragments. This patch accomplishes that
task.

rdar://157494251
---
 llvm/lib/MCCAS/MCCASObjectV1.cpp | 15 +++++++++++++++
 llvm/test/CAS/LEB-mccas.ll       | 28 ++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 llvm/test/CAS/LEB-mccas.ll

diff --git a/llvm/lib/MCCAS/MCCASObjectV1.cpp b/llvm/lib/MCCAS/MCCASObjectV1.cpp
index e35dcf9985c4f..4b3b85182bac7 100644
--- a/llvm/lib/MCCAS/MCCASObjectV1.cpp
+++ b/llvm/lib/MCCAS/MCCASObjectV1.cpp
@@ -1988,6 +1988,21 @@ Error MCDataFragmentMerger::emitMergedFragments() {
         return E;
       break;
     }
+    case MCFragment::FT_LEB: {
+      const MCLEBFragment *LEBF = cast<MCLEBFragment>(Candidate.first);
+      Builder.Asm.writeFragmentPadding(FragmentOS, *LEBF, Candidate.second);
+      FragmentData.append(CandidateContents);
+      break;
+    }
+
+    case MCFragment::FT_CVInlineLines: {
+      const MCCVInlineLineTableFragment *CVF =
+          cast<MCCVInlineLineTableFragment>(Candidate.first);
+      Builder.Asm.writeFragmentPadding(FragmentOS, *CVF, Candidate.second);
+      FragmentData.append(CandidateContents);
+      break;
+    }
+
     default:
       llvm_unreachable("other framgents should not be added");
     }
diff --git a/llvm/test/CAS/LEB-mccas.ll b/llvm/test/CAS/LEB-mccas.ll
new file mode 100644
index 0000000000000..54f2db390c7c0
--- /dev/null
+++ b/llvm/test/CAS/LEB-mccas.ll
@@ -0,0 +1,28 @@
+; This test was reduced using delta and llvm-reduce on a crash in MCCAS because
+; of an FT_LEB fragment which was attempted to be merged into an 
+; MCMergedFragmentRef. If MCCAS behaves correctly, llc should not crash when 
+; trying to create an MCCAS representation of this LLVM IR file.
+
+; RUN: rm -rf %t && mkdir -p %t
+; RUN: llc --filetype=obj --mccas-verify --cas-backend --cas-friendly-debug-info --cas=%t/cas %s -o %t/LEB.o 
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "arm64-apple-macosx14.0.0"
+
+; Function Attrs: noinline optnone
+define { ptr, i32 } @appendAnimation() #0 personality ptr @__objc_personality_v0 {
+  %1 = invoke ptr null(ptr null, ptr null)
+          to label %2 unwind label %3
+
+2:                                                ; preds = %0
+  ret { ptr, i32 } zeroinitializer
+
+3:                                                ; preds = %0
+  %4 = landingpad { ptr, i32 }
+          catch ptr null
+  ret { ptr, i32 } %4
+}
+
+declare i32 @__objc_personality_v0(...)
+
+attributes #0 = { noinline optnone }