[ThinLTO] Pass down opt level to LTO backend and handle -O0 LTO in new PM

Summary:
The opt level was not being passed down to the ThinLTO backend when
invoked via clang (for distributed ThinLTO).

This exposed an issue where the new PM was asserting if the Thin or
regular LTO backend pipelines were invoked with -O0 (not a new issue,
could be provoked by invoking in-process *LTO backends via linker using
new PM and -O0). Fix this similar to the old PM where -O0 only does the
necessary lowering of type metadata (WPD and LowerTypeTest passes) and
then quits, rather than asserting.

Reviewers: xur

Subscribers: mehdi_amini, inglorion, eraman, hiraditya, steven_wu, dexonsmith, cfe-commits, llvm-commits, pcc

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D61022

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@359025 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/BackendUtil.cpp

@@ -1325,6 +1325,7 @@ static void runThinLTOBackend(ModuleSummaryIndex *CombinedIndex, Module *M,
   Conf.MAttrs = TOpts.Features;
   Conf.RelocModel = CGOpts.RelocationModel;
   Conf.CGOptLevel = getCGOptLevel(CGOpts);
+  Conf.OptLevel = CGOpts.OptimizationLevel;
   initTargetOptions(Conf.Options, CGOpts, TOpts, LOpts, HeaderOpts);
   Conf.SampleProfile = std::move(SampleProfile);
 

test/CodeGen/thinlto-debug-pm.c

@@ -1,10 +1,17 @@
-// Test to ensure -fdebug-pass-manager works when invoking the
-// ThinLTO backend path with the new PM.
+// Test to ensure the opt level is passed down to the ThinLTO backend.
 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 -o %t.o -flto=thin -fexperimental-new-pass-manager -triple x86_64-unknown-linux-gnu -emit-llvm-bc %s
 // RUN: llvm-lto -thinlto -o %t %t.o
-// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-obj -O2 -o %t2.o -x ir %t.o -fthinlto-index=%t.thinlto.bc -fdebug-pass-manager -fexperimental-new-pass-manager 2>&1 | FileCheck %s
-// CHECK: Running pass:
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-obj -O2 -o %t2.o -x ir %t.o -fthinlto-index=%t.thinlto.bc -fdebug-pass-manager -fexperimental-new-pass-manager 2>&1 | FileCheck %s --check-prefix=O2-NEWPM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-obj -O0 -o %t2.o -x ir %t.o -fthinlto-index=%t.thinlto.bc -fdebug-pass-manager -fexperimental-new-pass-manager 2>&1 | FileCheck %s --check-prefix=O0-NEWPM
+// O2-NEWPM: Running pass: LoopVectorizePass
+// O0-NEWPM-NOT: Running pass: LoopVectorizePass
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-obj -O2 -o %t2.o -x ir %t.o -fthinlto-index=%t.thinlto.bc -mllvm -debug-pass=Structure 2>&1 | FileCheck %s --check-prefix=O2-OLDPM
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-obj -O0 -o %t2.o -x ir %t.o -fthinlto-index=%t.thinlto.bc -mllvm -debug-pass=Structure 2>&1 | FileCheck %s --check-prefix=O0-OLDPM
+// O2-OLDPM: Loop Vectorization
+// O0-OLDPM-NOT: Loop Vectorization
 
 void foo() {
 }

test/CodeGen/thinlto-distributed-cfi-devirt.ll

@@ -39,12 +39,12 @@
 ; CHECK-DIS: ^2 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: allOnes, sizeM1BitWidth: 7), wpdResolutions: ((offset: 0, wpdRes: (kind: branchFunnel)), (offset: 8, wpdRes: (kind: singleImpl, singleImplName: "_ZN1A1nEi"))))) ; guid = 7004155349499253778
 
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \
-; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc \
+; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc -O2 \
 ; RUN:   -emit-llvm -o - -x ir %t.o | FileCheck %s --check-prefixes=CHECK-IR
 
 ; Check that backend does not fail generating native code.
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \
-; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc \
+; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc -O2 \
 ; RUN:   -o %t.native.o -x ir %t.o
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"