Use CodegenOpts::less when creating a TargetMachine for clang `-O1`

Summary:
Clang was initializing the TargetMachine with CodeGenOpt::Default
for O1. This change is aligning it on llc:

-O0: OptLevel = CodeGenOpt::None
-O1: OptLevel = CodeGenOpt::Less
-O2 -Os -Oz: OptLevel = CodeGenOpt::Default
-O3: OptLevel = CodeGenOpt::Aggressive

Reviewers: echristo, chandlerc

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D28409

llvm-svn: 291276

1 files changed, 15 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index ed09f3a4556..8dd1623ee2c 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -519,11 +519,22 @@ void EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
            .Case("dynamic-no-pic", llvm::Reloc::DynamicNoPIC);
   assert(RM.hasValue() && "invalid PIC model!");
 
-  CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
+  CodeGenOpt::Level OptLevel;
   switch (CodeGenOpts.OptimizationLevel) {
-  default: break;
-  case 0: OptLevel = CodeGenOpt::None; break;
-  case 3: OptLevel = CodeGenOpt::Aggressive; break;
+  default:
+    llvm_unreachable("Invalid optimization level!");
+  case 0:
+    OptLevel = CodeGenOpt::None;
+    break;
+  case 1:
+    OptLevel = CodeGenOpt::Less;
+    break;
+  case 2:
+    OptLevel = CodeGenOpt::Default;
+    break; // O2/Os/Oz
+  case 3:
+    OptLevel = CodeGenOpt::Aggressive;
+    break;
   }
 
   llvm::TargetOptions Options;