[flang][driver] Fix opt-level option parsing

[awarzynski]

Summary

This update makes sure that flang-new -O2 -O0 will run at -O0 rather
than -O2.

This bug was identified and originally fixed by Vyacheslav Zakharin in
https://reviews.llvm.org/D130035. I've extracted the fix into a separate
patch.

co-authored by: Vyacheslav Zakharin <[e-mail]>

[vzakhari]

Thanks for taking care of it! LGTM except for the typo.

flang/lib/Frontend/CompilerInvocation.cpp

93

typo: "from from"

[awarzynski]

flang/lib/Frontend/CompilerInvocation.cpp

93

Cheers, will fix before merging

[clementval]

Co-authored-by: must be on the last line of the commit message otherwise authorship is not acknoledge correctly by github. So for github, on this commit https://github.com/llvm/llvm-project/commit/bbdf5c37e38e172228963fed8ebc3c37d940ede1 you are the only author.

[awarzynski]

In D130104#3665300, @clementval wrote:

Co-authored-by: must be on the last line of the commit message otherwise authorship is not acknoledge correctly by github. So for github, on this commit https://github.com/llvm/llvm-project/commit/bbdf5c37e38e172228963fed8ebc3c37d940ede1 you are the only author.

Sorry about that! TBH, I pay little attention to GitHub statistics, but I appreciate that others might find it helpful. Why not formalize this by updating https://llvm.org/docs/Contributing.html?

Hopefully one day there will be a Git hook to automate this. Or perhaps there is one that I'm not aware of?

[vzakhari]

@awarzynski I wonder where I still have my old e-mail [e-mail] referenced - can you please point me to it?

[awarzynski]

In D130104#3667060, @vzakhari wrote:

@awarzynski I wonder where I still have my old e-mail [e-mail] referenced - can you please point me to it?

git log inside the LLVM repo. I searched for "Vyacheslav" (which I took from Phabricator, but that has changed since, hasn't it?).

[vzakhari]

In D130104#3667832, @awarzynski wrote:

In D130104#3667060, @vzakhari wrote:

@awarzynski I wonder where I still have my old e-mail [e-mail] referenced - can you please point me to it?

git log inside the LLVM repo. I searched for "Vyacheslav" (which I took from Phabricator, but that has changed since, hasn't it?).

Ah, okay :) yes, I changed first name in phabricator, so using git log looking for Slava Zakharin should now give you my current mail.

flang/lib/Frontend/CompilerInvocation.cpp

for (auto *a : args) {
     }
   }
 
   return showColors == Colors_On ||
          (showColors == Colors_Auto &&
           llvm::sys::Process::StandardErrHasColors());
 }
 
+/// Extracts the optimisation level from \a args.
+static unsigned getOptimizationLevel(llvm::opt::ArgList &args,
+                                     clang::DiagnosticsEngine &diags) {
+  unsigned defaultOpt = llvm::CodeGenOpt::None;
+
+  if (llvm::opt::Arg *a =
+          args.getLastArg(clang::driver::options::OPT_O_Group)) {
+    if (a->getOption().matches(clang::driver::options::OPT_O0))
+      return llvm::CodeGenOpt::None;
+
+    assert(a->getOption().matches(clang::driver::options::OPT_O));
+
+    return getLastArgIntValue(args, clang::driver::options::OPT_O, defaultOpt,
+                              diags);
+  }
+
+  return defaultOpt;
+}
+
 bool Fortran::frontend::parseDiagnosticArgs(clang::DiagnosticOptions &opts,
                                             llvm::opt::ArgList &args) {
   opts.ShowColors = parseShowColorsArgs(args);
 
   return true;
 }
 
 static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
                              llvm::opt::ArgList &args,
                              clang::DiagnosticsEngine &diags) {
-  unsigned defaultOpt = llvm::CodeGenOpt::None;
-  opts.OptimizationLevel = clang::getLastArgIntValue(
-      args, clang::driver::options::OPT_O, defaultOpt, diags);
+  opts.OptimizationLevel = getOptimizationLevel(args, diags);
 
   if (args.hasFlag(clang::driver::options::OPT_fdebug_pass_manager,
                    clang::driver::options::OPT_fno_debug_pass_manager, false))
     opts.DebugPassManager = 1;
 }
 
 /// Parses all target input arguments and populates the target
 /// options accordingly.

flang/test/Driver/default-optimization-pipelines.f90

 ! Verify that`-O{n}` is indeed taken into account when defining the LLVM optimization/middle-end pass pipeline.
 
 ! RUN: %flang -S -O0 %s -Xflang -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O0
 ! RUN: %flang_fc1 -S -O0 %s -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O0
 
 ! RUN: %flang -S -O2 %s -Xflang -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O2
 ! RUN: %flang_fc1 -S -O2 %s -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O2
 
+! Verify that only the left-most `-O{n}` is used
+! RUN: %flang -S -O2 -O0 %s -Xflang -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O0
+! RUN: %flang_fc1 -S -O2 -O0 %s -fdebug-pass-manager -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-O0
+
 ! CHECK-O0-NOT: Running pass: SimplifyCFGPass on simple_loop_
 ! CHECK-O0: Running analysis: TargetLibraryAnalysis on simple_loop_
 
 ! CHECK-O2: Running pass: SimplifyCFGPass on simple_loop_
 
 subroutine simple_loop
   integer :: i
   do i=1,5
   end do
 end subroutine