Using an invalid -O falls back on -O3 instead of an error

Summary:
Currently with clang:
$ clang -O20 foo.c
error: invalid value '20' in '-O20'

With the patch:
$ clang -O20 foo.c
warning: optimization level '-O20' is unsupported; using '-O3' instead.
1 warning generated.

This matches the gcc behavior (with a warning added)

Pass all tests:
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 94.14s
  Expected Passes    : 6721
  Expected Failures  : 20
  Unsupported Tests  : 17

(which was not the case of http://llvm-reviews.chandlerc.com/D2125)

Differential Revision: http://llvm-reviews.chandlerc.com/D2212

llvm-svn: 195009

1 files changed, 8 insertions, 7 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 94a3a33235a..8db5cf1bc21 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -299,14 +299,15 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   using namespace options;
   bool Success = true;
 
-  unsigned OptLevel = getOptimizationLevel(Args, IK, Diags);
-  if (OptLevel > 3) {
-    Diags.Report(diag::err_drv_invalid_value)
-      << Args.getLastArg(OPT_O)->getAsString(Args) << OptLevel;
-    OptLevel = 3;
-    Success = false;
+  Opts.OptimizationLevel = getOptimizationLevel(Args, IK, Diags);
+  // TODO: This could be done in Driver
+  unsigned MaxOptLevel = 3;
+  if (Opts.OptimizationLevel > MaxOptLevel) {
+    // If the optimization level is not supported, fall back on the default optimization
+    Diags.Report(diag::warn_drv_optimization_value)
+        << Args.getLastArg(OPT_O)->getAsString(Args) << "-O" << MaxOptLevel;
+    Opts.OptimizationLevel = MaxOptLevel;
   }
-  Opts.OptimizationLevel = OptLevel;
 
   // We must always run at least the always inlining pass.
   Opts.setInlining(