[LTO] Enable module summary emission by default for regular LTO

Summary:
With D33921, we gained the ability to have module summaries in regular
LTO modules without triggering ThinLTO compilation. Module summaries in
regular LTO allow garbage collection (dead stripping) before LTO
compilation and thus open up additional optimization opportunities.

This patch enables summary emission in regular LTO for all targets
except ld64-based ones (which use the legacy LTO API).

Reviewers: pcc, tejohnson, mehdi_amini

Subscribers: inglorion, eraman, cfe-commits

Differential Revision: https://reviews.llvm.org/D34156

llvm-svn: 335284

6 files changed, 49 insertions, 18 deletions

diff --git a/clang/include/clang/Frontend/CodeGenOptions.def b/clang/include/clang/Frontend/CodeGenOptions.def
index 019425d1946..99567e04ba6 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.def
+++ b/clang/include/clang/Frontend/CodeGenOptions.def
@@ -110,7 +110,7 @@ CODEGENOPT(LessPreciseFPMAD  , 1, 0) ///< Enable less precise MAD instructions t
                                      ///< be generated.
 CODEGENOPT(PrepareForLTO     , 1, 0) ///< Set when -flto is enabled on the
                                      ///< compile step.
-CODEGENOPT(EmitSummaryIndex, 1, 0)   ///< Set when -flto=thin is enabled on the
+CODEGENOPT(PrepareForThinLTO , 1, 0) ///< Set when -flto=thin is enabled on the
                                      ///< compile step.
 CODEGENOPT(LTOUnit, 1, 0) ///< Emit IR to support LTO unit features (CFI, whole
                           ///< program vtable opt).
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 4125d507a1e..b06c68fe742 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -524,7 +524,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
     PMBuilder.Inliner = createFunctionInliningPass(
         CodeGenOpts.OptimizationLevel, CodeGenOpts.OptimizeSize,
         (!CodeGenOpts.SampleProfileFile.empty() &&
-         CodeGenOpts.EmitSummaryIndex));
+         CodeGenOpts.PrepareForThinLTO));
   }
 
   PMBuilder.OptLevel = CodeGenOpts.OptimizationLevel;
@@ -534,7 +534,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
 
   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
   PMBuilder.MergeFunctions = CodeGenOpts.MergeFunctions;
-  PMBuilder.PrepareForThinLTO = CodeGenOpts.EmitSummaryIndex;
+  PMBuilder.PrepareForThinLTO = CodeGenOpts.PrepareForThinLTO;
   PMBuilder.PrepareForLTO = CodeGenOpts.PrepareForLTO;
   PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
 
@@ -776,7 +776,7 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
     break;
 
   case Backend_EmitBC:
-    if (CodeGenOpts.EmitSummaryIndex) {
+    if (CodeGenOpts.PrepareForThinLTO) {
       if (!CodeGenOpts.ThinLinkBitcodeFile.empty()) {
         ThinLinkOS = openOutputFile(CodeGenOpts.ThinLinkBitcodeFile);
         if (!ThinLinkOS)
@@ -784,10 +784,20 @@ void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
       }
       PerModulePasses.add(createWriteThinLTOBitcodePass(
           *OS, ThinLinkOS ? &ThinLinkOS->os() : nullptr));
-    }
-    else
+    } else {
+      // Emit a module summary by default for Regular LTO except for ld64
+      // targets
+      bool EmitLTOSummary =
+          (CodeGenOpts.PrepareForLTO &&
+           llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
+               llvm::Triple::Apple);
+      if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
+        TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
+
       PerModulePasses.add(
-          createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists));
+          createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
+                                  EmitLTOSummary));
+    }
     break;
 
   case Backend_EmitLL:
@@ -935,7 +945,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
   ModulePassManager MPM(CodeGenOpts.DebugPassManager);
 
   if (!CodeGenOpts.DisableLLVMPasses) {
-    bool IsThinLTO = CodeGenOpts.EmitSummaryIndex;
+    bool IsThinLTO = CodeGenOpts.PrepareForThinLTO;
     bool IsLTO = CodeGenOpts.PrepareForLTO;
 
     if (CodeGenOpts.OptimizationLevel == 0) {
@@ -996,7 +1006,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
     break;
 
   case Backend_EmitBC:
-    if (CodeGenOpts.EmitSummaryIndex) {
+    if (CodeGenOpts.PrepareForThinLTO) {
       if (!CodeGenOpts.ThinLinkBitcodeFile.empty()) {
         ThinLinkOS = openOutputFile(CodeGenOpts.ThinLinkBitcodeFile);
         if (!ThinLinkOS)
@@ -1005,9 +1015,17 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
       MPM.addPass(ThinLTOBitcodeWriterPass(*OS, ThinLinkOS ? &ThinLinkOS->os()
                                                            : nullptr));
     } else {
+      // Emit a module summary by default for Regular LTO except for ld64
+      // targets
+      bool EmitLTOSummary =
+          (CodeGenOpts.PrepareForLTO &&
+           llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
+               llvm::Triple::Apple);
+      if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
+        TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
+
       MPM.addPass(BitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
-                                    CodeGenOpts.EmitSummaryIndex,
-                                    CodeGenOpts.EmitSummaryIndex));
+                                    EmitLTOSummary));
     }
     break;
 
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 3ca6459a6a3..a0d5fd62360 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -578,7 +578,7 @@ void CGDebugInfo::CreateCompileUnit() {
                           CSInfo,
                           getSource(SM, SM.getMainFileID())),
       CGOpts.EmitVersionIdentMetadata ? Producer : "",
-      LO.Optimize || CGOpts.PrepareForLTO || CGOpts.EmitSummaryIndex,
+      LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
       CGOpts.DwarfDebugFlags, RuntimeVers,
       CGOpts.EnableSplitDwarf ? "" : CGOpts.SplitDwarfFile, EmissionKind,
       0 /* DWOid */, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 1f9d6b0d7f5..60ed5fdf708 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -749,11 +749,11 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.ProfileSampleAccurate = Args.hasArg(OPT_fprofile_sample_accurate);
 
   Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
-  Opts.EmitSummaryIndex = false;
+  Opts.PrepareForThinLTO = false;
   if (Arg *A = Args.getLastArg(OPT_flto_EQ)) {
     StringRef S = A->getValue();
     if (S == "thin")
-      Opts.EmitSummaryIndex = true;
+      Opts.PrepareForThinLTO = true;
     else if (S != "full")
       Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << S;
   }
diff --git a/clang/test/CodeGen/emit-summary-index.c b/clang/test/CodeGen/emit-summary-index.c
new file mode 100644
index 00000000000..61264102068
--- /dev/null
+++ b/clang/test/CodeGen/emit-summary-index.c
@@ -0,0 +1,17 @@
+// ; Check that the -flto=thin option emits a ThinLTO summary
+// RUN: %clang_cc1 -flto=thin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck %s
+// CHECK: <GLOBALVAL_SUMMARY_BLOCK
+//
+// ; Check that we do not emit a summary for regular LTO on Apple platforms
+// RUN: %clang_cc1 -flto -triple x86_64-apple-darwin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTO %s
+// LTO-NOT: GLOBALVAL_SUMMARY_BLOCK
+//
+// ; Check that we emit a summary for regular LTO by default elsewhere
+// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTOINDEX %s
+// LTOINDEX: <FULL_LTO_GLOBALVAL_SUMMARY_BLOCK
+//
+// ; Simulate -save-temps and check that it works (!"ThinLTO" module flag not added multiple times)
+// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc -disable-llvm-passes < %s -o %t.bc
+// RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc -x ir < %t.bc | llvm-bcanalyzer -dump | FileCheck --check-prefix=LTOINDEX %s
+
+int main() {}
diff --git a/clang/test/Misc/thinlto.c b/clang/test/Misc/thinlto.c
deleted file mode 100644
index ec0f03f5a2a..00000000000
--- a/clang/test/Misc/thinlto.c
+++ /dev/null
@@ -1,4 +0,0 @@
-// RUN: %clang_cc1 -flto=thin -emit-llvm-bc < %s | llvm-bcanalyzer -dump | FileCheck %s
-// ; Check that the -flto=thin option emits a summary
-// CHECK: <GLOBALVAL_SUMMARY_BLOCK
-int main() {}