[clang] [flang] [flang][driver] Accept -fallow-argument-mismatch with a warning instead of rejecting it (PR #91611)

[Paul Osmialowski via cfe-commits]

https://github.com/pawosm-arm created https://github.com/llvm/llvm-project/pull/91611

Many autotools-utilizing projects (mpich among them) fail to complete the `configure` step since it tries to invoke the (unknown to them) Fortran compiler always with the `-fallow-argument-mismatch` flag.

As the use of this flag has no impact on flang, there is no definite need to reject it. It would be better to accept it with a warning and reject the opposite flag `-fno-allow-argument-mismatch` with an error.

With this patch, mpich compiles and works.


>From afeb4498c0f5b9f4e41e486b28caa0603740ae2c Mon Sep 17 00:00:00 2001
From: Paul Osmialowski <pawel.osmialowski at arm.com>
Date: Thu, 9 May 2024 16:23:38 +0100
Subject: [PATCH] [flang][driver] Accept -fallow-argument-mismatch with a
 warning instead of rejecting it

Many autotools-utilizing projects (mpich among them) fail to complete
the `configure` step since it tries to invoke the (unknown to them)
Fortran compiler always with the `-fallow-argument-mismatch` flag.

As the use of this flag has no impact on flang, there is no definite
need to reject it. It would be better to accept it with a warning and
reject the opposite flag `-fno-allow-argument-mismatch` with an error.
---
 clang/include/clang/Driver/Options.td         |  2 ++
 flang/test/Driver/allow-argument-mismatch.f90 | 15 +++++++++++++++
 2 files changed, 17 insertions(+)
 create mode 100644 flang/test/Driver/allow-argument-mismatch.f90

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 73a2518480e9b..eaa17fdec0f8b 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2540,6 +2540,8 @@ def fsanitize_undefined_strip_path_components_EQ : Joined<["-"], "fsanitize-unde
 
 } // end -f[no-]sanitize* flags
 
+def fallow_argument_mismatch : Flag<["-"], "fallow-argument-mismatch">, Visibility<[FlangOption, FC1Option]>;
+
 def funsafe_math_optimizations : Flag<["-"], "funsafe-math-optimizations">,
   Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Allow unsafe floating-point math optimizations which may decrease precision">,
diff --git a/flang/test/Driver/allow-argument-mismatch.f90 b/flang/test/Driver/allow-argument-mismatch.f90
new file mode 100644
index 0000000000000..2adf9e67daeab
--- /dev/null
+++ b/flang/test/Driver/allow-argument-mismatch.f90
@@ -0,0 +1,15 @@
+! Test that -fallow-argument-mismatch flag is accepted with warning, while
+! -fno-allow-argument-mismatch is rejected with error
+
+! RUN: %flang -S %s -fallow-argument-mismatch -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-WARNING
+! RUN: %flang_fc1 -S %s -fallow-argument-mismatch -o /dev/null
+! RUN: not %flang -S %s -fno-allow-argument-mismatch -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR
+! RUN: not %flang_fc1 -S %s -fno-allow-argument-mismatch -o /dev/null 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR
+
+! CHECK-WARNING: warning:
+! CHECK_WARNING-SAME: argument unused
+! CHECK_WARNING-SAME: -fallow-argument-mismatch
+
+! CHECK-ERROR: error:
+! CHECK-ERROR-SAME: unknown argument
+! CHECK-ERROR-SAME: -fno-allow-argument-mismatch