From 1cd76b1a44d74e9e2e8b8fcacc2d7ec290b54b76 Mon Sep 17 00:00:00 2001
From: Sylvestre Ledru <sylvestre@debian.org>
Date: Mon, 11 Nov 2013 19:01:05 +0000
Subject: [PATCH] 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: invalid value '20' in '-O20'. Fall back on value '3'

Reviewers: rengolin, hfinkel

Reviewed By: rengolin

CC: cfe-commits, hfinkel, rengolin

Differential Revision: http://llvm-reviews.chandlerc.com/D2125

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194403 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticDriverKinds.td |  1 +
 lib/Driver/Tools.cpp                         |  2 +-
 lib/Frontend/CompilerInvocation.cpp          | 14 +++++++-------
 test/Driver/clang_f_opts.c                   |  3 +++
 4 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/clang/Basic/DiagnosticDriverKinds.td b/include/clang/Basic/DiagnosticDriverKinds.td
index ed49006b21..b14a3b6a55 100644
--- a/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/include/clang/Basic/DiagnosticDriverKinds.td
@@ -113,6 +113,7 @@ def err_drv_unknown_toolchain : Error<
   "cannot recognize the type of the toolchain">;
 
 def warn_O4_is_O3 : Warning<"-O4 is equivalent to -O3">, InGroup<Deprecated>;
+def warn_drv_invalid_value : Warning<"optimization level '%0' is unsupported; using '%1%2' instead.">;
 def warn_c_kext : Warning<
   "ignoring -fapple-kext which is valid for C++ and Objective-C++ only">;
 def warn_drv_input_file_unused : Warning<
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index c69ad53360..87ec76350e 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2727,7 +2727,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // preprocessed inputs and configure concludes that -fPIC is not supported.
   Args.ClaimAllArgs(options::OPT_D);
 
-  // Manually translate -O4 to -O3; let clang reject others.
+  // Manually translate -O4 to -O3; let clang fall back on -O3 for others
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
     if (A->getOption().matches(options::OPT_O4)) {
       CmdArgs.push_back("-O3");
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 98745aca68..d02e4a3e98 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -299,14 +299,14 @@ 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);
+  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_invalid_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(
diff --git a/test/Driver/clang_f_opts.c b/test/Driver/clang_f_opts.c
index e8375838dc..462b11a112 100644
--- a/test/Driver/clang_f_opts.c
+++ b/test/Driver/clang_f_opts.c
@@ -100,6 +100,9 @@
 // CHECK-MAX-O: warning: -O4 is equivalent to -O3
 // CHECK-MAX-O: -O3
 
+// RUN: %clang -### -S -O20 %s 2>&1 | FileCheck -check-prefix=CHECK-INVALID-O %s
+// CHECK-INVALID-O: warning: optimization level '-O20' is unsupported; using '-O3' instead.
+
 // Test that we don't error on these.
 // RUN: %clang -### -S -Werror                                                \
 // RUN:     -falign-functions -falign-functions=2 -fno-align-functions        \
-- 
2.40.0