Cherry-pick https://github.com/swiftlang/llvm-project/pull/9164 to next

clang/lib/Frontend/CompileJobCache.cpp

@@ -724,7 +724,7 @@ Error ObjectStoreCachingOutputs::finishComputedResult(
 std::optional<int> ObjectStoreCachingOutputs::replayCachedResult(
     const llvm::cas::CASID &ResultCacheKey, llvm::cas::ObjectRef ResultID,
     bool JustComputedResult) {
-  if (JustComputedResult && !ComputedJobNeedsReplay)
+  if (JustComputedResult && !WriteOutputAsCASID)
     return std::nullopt;
 
   // FIXME: Stop calling report_fatal_error().
@@ -745,10 +745,7 @@ std::optional<int> ObjectStoreCachingOutputs::replayCachedResult(
 Expected<std::optional<int>> ObjectStoreCachingOutputs::replayCachedResult(
     const llvm::cas::CASID &ResultCacheKey,
     clang::cas::CompileJobCacheResult &Result, bool JustComputedResult) {
-  // FIXME: The correct fix for MCCAS replay is that you have an official CASID
-  // file output going all the way down into ObjectWriter, we can remove this
-  // callback and special case.
-  if (JustComputedResult && !ComputedJobNeedsReplay)
+  if (JustComputedResult && !WriteOutputAsCASID)
     return std::nullopt;
 
   llvm::cas::ObjectStore &CAS = Result.getCAS();

clang/test/CAS/cas-backend.c

@@ -1,7 +1,7 @@
 // RUN: rm -rf %t && mkdir -p %t
 // RUN: llvm-cas --cas %t/cas --ingest %s > %t/casid
 //
-// RUN: %clang -cc1 -triple x86_64-apple-macos11 -fcas-backend \
+// RUN: %clang -cc1 -fcas-emit-casid-file -triple x86_64-apple-macos11 -fcas-backend \
 // RUN:   -fcas-path %t/cas -fcas-fs @%t/casid -fcache-compile-job \
 // RUN:   -Rcompile-job-cache %s -emit-obj -o %t/output.o \
 // RUN:   -debug-info-kind=standalone -dwarf-version=4 -debugger-tuning=lldb \
@@ -11,7 +11,7 @@
 // RUN: ls %t/output.o && rm %t/output.o
 // RUN: ls %t/deps.d && mv %t/deps.d %t/deps.d.orig
 //
-// RUN: CLANG_CAS_BACKEND_SAVE_CASID_FILE=1 %clang -cc1 \
+// RUN: %clang -cc1 -fcas-emit-casid-file\
 // RUN:   -triple x86_64-apple-macos11 -fcas-backend \
 // RUN:   -fcas-path %t/cas -fcas-fs @%t/casid -fcache-compile-job \
 // RUN:   -Rcompile-job-cache %s -emit-obj -o %t/output.o \

clang/test/CAS/casid-output-test.cpp

@@ -0,0 +1,25 @@
+// RUN: rm -rf %t && mkdir -p %t
+
+// Check if -fcasid-output works on a cache miss with file based caching
+// RUN: env LLVM_CACHE_CAS_PATH=%t/cas CLANG_CACHE_DISABLE_MCCAS=1 %clang-cache %clang -target x86_64-apple-macos11 -Xclang -fcasid-output -g -c %s -o %t/test.o
+// RUN: cat %t/test.o | FileCheck %s
+// RUN: rm -rf %t/test.o
+// Check if -fcasid-output works on a cache hit with file based caching
+// RUN: env LLVM_CACHE_CAS_PATH=%t/cas CLANG_CACHE_DISABLE_MCCAS=1 %clang-cache %clang -target x86_64-apple-macos11 -Xclang -fcasid-output -g -c %s -o %t/test.o
+// RUN: cat %t/test.o | FileCheck %s
+// RUN: rm -rf %t/test.o
+// RUN: rm -rf %t/cas
+
+// Check if -fcasid-output works on a cache miss with MCCAS
+// RUN: env LLVM_CACHE_CAS_PATH=%t/cas %clang-cache %clang -target x86_64-apple-macos11 -Xclang -fcasid-output -g -c %s -o %t/test.o
+// RUN: cat %t/test.o | FileCheck %s
+// RUN: rm -rf %t/test.o
+
+// Check if -fcasid-output works on a cache hit with MCCAS
+// RUN: env LLVM_CACHE_CAS_PATH=%t/cas %clang-cache %clang -target x86_64-apple-macos11 -Xclang -fcasid-output -g -c %s -o %t/test.o
+// RUN: cat %t/test.o | FileCheck %s
+
+// CHECK: llvmcas://{{[a-f0-9]+}}
+
+
+void foo() {}

llvm/lib/MC/MachOCASWriter.cpp

@@ -76,6 +76,7 @@ uint64_t MachOCASWriter::writeObject(MCAssembler &Asm) {
           inconvertibleErrorCode(),
           "CASBackend output round-trip verification error");
 
+    OS << ObjectBuffer;
     return Error::success();
   };
 
@@ -85,11 +86,6 @@ uint64_t MachOCASWriter::writeObject(MCAssembler &Asm) {
   // If there is a callback, then just hand off the result through callback.
   if (ResultCallBack) {
     cantFail((*ResultCallBack)(CASObj.getID()));
-    if (Mode == CASBackendMode::Verify) {
-      if (auto E = VerifyObject())
-        report_fatal_error(std::move(E));
-    }
-    return 0;
   }
 
   switch (Mode) {
@@ -103,17 +99,8 @@ uint64_t MachOCASWriter::writeObject(MCAssembler &Asm) {
     break;
   }
   case CASBackendMode::Verify: {
-    SmallString<512> ObjectBuffer;
-    raw_svector_ostream ObjectOS(ObjectBuffer);
-    auto E = SerializeObjectFile(CASObj, CAS, ObjectOS);
-    if (E)
+    if (auto E = VerifyObject())
       report_fatal_error(std::move(E));
-
-    if (!ObjectBuffer.equals(InternalBuffer))
-      report_fatal_error("CASBackend output round-trip verification error");
-
-    OS << ObjectBuffer;
-    break;
   }
   }