From 80186a57d66c4374aea9118045d8489dcdb6071b Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Fri, 23 Sep 2016 21:33:43 +0000
Subject: LTO: Simplify caching interface.

The NativeObjectOutput class has a design problem: it mixes up the caching
policy with the interface for output streams, which makes the client-side
code hard to follow and would for example make it harder to replace the
cache implementation in an arbitrary client.

This change separates the two aspects by moving the caching policy
to a separate field in Config, replacing NativeObjectOutput with a
NativeObjectStream class which only deals with streams and does not need to
be overridden by most clients and introducing an AddFile callback for adding
files (e.g. from the cache) to the link.

Differential Revision: https://reviews.llvm.org/D24622

llvm-svn: 282299
---
 llvm/lib/LTO/LTOBackend.cpp | 38 +++++++++++---------------------------
 1 file changed, 11 insertions(+), 27 deletions(-)

(limited to 'llvm/lib/LTO/LTOBackend.cpp')

diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index d83b65de4cc..96215b78498 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -199,34 +199,20 @@ bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
   return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
 }
 
-/// Monolithic LTO does not support caching (yet), this is a convenient wrapper
-/// around AddOutput to workaround this.
-static AddOutputFn getUncachedOutputWrapper(AddOutputFn &AddOutput,
-                                            unsigned Task) {
-  return [Task, &AddOutput](unsigned TaskId) {
-    auto Output = AddOutput(Task);
-    if (Output->isCachingEnabled() && Output->tryLoadFromCache(""))
-      report_fatal_error("Cache hit without a valid key?");
-    assert(Task == TaskId && "Unexpexted TaskId mismatch");
-    return Output;
-  };
-}
-
-void codegen(Config &Conf, TargetMachine *TM, AddOutputFn AddOutput,
+void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod) {
   if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
     return;
 
-  auto Output = AddOutput(Task);
-  std::unique_ptr<raw_pwrite_stream> OS = Output->getStream();
+  auto Stream = AddStream(Task);
   legacy::PassManager CodeGenPasses;
-  if (TM->addPassesToEmitFile(CodeGenPasses, *OS,
+  if (TM->addPassesToEmitFile(CodeGenPasses, *Stream->OS,
                               TargetMachine::CGFT_ObjectFile))
     report_fatal_error("Failed to setup codegen");
   CodeGenPasses.run(Mod);
 }
 
-void splitCodeGen(Config &C, TargetMachine *TM, AddOutputFn AddOutput,
+void splitCodeGen(Config &C, TargetMachine *TM, AddStreamFn AddStream,
                   unsigned ParallelCodeGenParallelismLevel,
                   std::unique_ptr<Module> Mod) {
   ThreadPool CodegenThreadPool(ParallelCodeGenParallelismLevel);
@@ -260,9 +246,7 @@ void splitCodeGen(Config &C, TargetMachine *TM, AddOutputFn AddOutput,
               std::unique_ptr<TargetMachine> TM =
                   createTargetMachine(C, MPartInCtx->getTargetTriple(), T);
 
-              codegen(C, TM.get(),
-                      getUncachedOutputWrapper(AddOutput, ThreadId), ThreadId,
-                      *MPartInCtx);
+              codegen(C, TM.get(), AddStream, ThreadId, *MPartInCtx);
             },
             // Pass BC using std::move to ensure that it get moved rather than
             // copied into the thread's context.
@@ -299,7 +283,7 @@ static void handleAsmUndefinedRefs(Module &Mod, TargetMachine &TM) {
   updateCompilerUsed(Mod, TM, AsmUndefinedRefs);
 }
 
-Error lto::backend(Config &C, AddOutputFn AddOutput,
+Error lto::backend(Config &C, AddStreamFn AddStream,
                    unsigned ParallelCodeGenParallelismLevel,
                    std::unique_ptr<Module> Mod) {
   Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod);
@@ -316,15 +300,15 @@ Error lto::backend(Config &C, AddOutputFn AddOutput,
       return Error();
 
   if (ParallelCodeGenParallelismLevel == 1) {
-    codegen(C, TM.get(), getUncachedOutputWrapper(AddOutput, 0), 0, *Mod);
+    codegen(C, TM.get(), AddStream, 0, *Mod);
   } else {
-    splitCodeGen(C, TM.get(), AddOutput, ParallelCodeGenParallelismLevel,
+    splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,
                  std::move(Mod));
   }
   return Error();
 }
 
-Error lto::thinBackend(Config &Conf, unsigned Task, AddOutputFn AddOutput,
+Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
                        Module &Mod, ModuleSummaryIndex &CombinedIndex,
                        const FunctionImporter::ImportMapTy &ImportList,
                        const GVSummaryMapTy &DefinedGlobals,
@@ -339,7 +323,7 @@ Error lto::thinBackend(Config &Conf, unsigned Task, AddOutputFn AddOutput,
   handleAsmUndefinedRefs(Mod, *TM);
 
   if (Conf.CodeGenOnly) {
-    codegen(Conf, TM.get(), AddOutput, Task, Mod);
+    codegen(Conf, TM.get(), AddStream, Task, Mod);
     return Error();
   }
 
@@ -379,6 +363,6 @@ Error lto::thinBackend(Config &Conf, unsigned Task, AddOutputFn AddOutput,
   if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLto=*/true))
     return Error();
 
-  codegen(Conf, TM.get(), AddOutput, Task, Mod);
+  codegen(Conf, TM.get(), AddStream, Task, Mod);
   return Error();
 }
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