[flang][Driver] Add -masm option to flang

[DavidSpickett]

The motivation here was a suggestion over in Compiler Explorer. You can use -mllvm already to do this but since gfortran supports -masm, I figured I'd try to add it.

This is done by flang expanding -masm into -mllvm x86-asm-syntax=, then passing that to fc1. Which then collects all the -mllvm options and forwards them on.

The code to expand it comes from clang Clang::AddX86TargetArgs (there are some other places doing the same thing too). However I've removed the -inline-asm that clang adds, as fortran doesn't have inline assembly.

So -masm for flang purely changes the style of assembly output.

$ ./bin/flang-new /tmp/test.f90 -o - -S -target x86_64-linux-gnu
<...>
        pushq   %rbp
$ ./bin/flang-new /tmp/test.f90 -o - -S -target x86_64-linux-gnu -masm=att
<...>
        pushq   %rbp
$ ./bin/flang-new /tmp/test.f90 -o - -S -target x86_64-linux-gnu -masm=intel
<...>
        push    rbp

The test is adapted from clang/test/Driver/masm.c by removing the clang-cl related lines and changing the 32 bit triples to 64 bit triples since flang doesn't support 32 bit targets.

[llvmbot]

@llvm/pr-subscribers-flang-driver
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: David Spickett (DavidSpickett)

Changes

The motivation here was a suggestion over in Compiler Explorer. You can use -mllvm already to do this but since gfortran supports -masm, I figured I'd try to add it.

This is done by flang expanding -masm into -mllvm x86-asm-syntax=, then passing that to fc1. Which then collects all the -mllvm options and forwards them on.

The code to expand it comes from clang Clang::AddX86TargetArgs (there are some other places doing the same thing too). However I've removed the -inline-asm that clang adds, as fortran doesn't have inline assembly.

So -masm for flang purely changes the style of assembly output.

The test is adapted from clang/test/Driver/masm.c by removing the clang-cl related lines and changing the 32 bit triples to 64 bit triples since flang doesn't support 32 bit targets.

---

Full diff: https://github.com/llvm/llvm-project/pull/81490.diff

4 Files Affected:

• (modified) clang/include/clang/Driver/Options.td (+1-1)
• (modified) clang/lib/Driver/ToolChains/Flang.cpp (+15)
• (modified) clang/lib/Driver/ToolChains/Flang.h (+7)
• (added) flang/test/Driver/masm.f90 (+13)

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 31e8571758bfce..d5017b901d2906 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4414,7 +4414,7 @@ def mwatchsimulator_version_min_EQ : Joined<["-"], "mwatchsimulator-version-min=
 def march_EQ : Joined<["-"], "march=">, Group<m_Group>,
   Flags<[TargetSpecific]>, Visibility<[ClangOption, CLOption, DXCOption, FlangOption]>,
   HelpText<"For a list of available architectures for the target use '-mcpu=help'">;
-def masm_EQ : Joined<["-"], "masm=">, Group<m_Group>;
+def masm_EQ : Joined<["-"], "masm=">, Group<m_Group>, Visibility<[ClangOption, FlangOption]>;
 def inline_asm_EQ : Joined<["-"], "inline-asm=">, Group<m_Group>,
   Visibility<[ClangOption, CC1Option]>,
   Values<"att,intel">,
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index 23da08aa593f2d..6168b42dc78292 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -249,6 +249,20 @@ void Flang::AddRISCVTargetArgs(const ArgList &Args,
   }
 }
 
+void Flang::AddX86_64TargetArgs(const ArgList &Args,
+                                ArgStringList &CmdArgs) const {
+  if (Arg *A = Args.getLastArg(options::OPT_masm_EQ)) {
+    StringRef Value = A->getValue();
+    if (Value == "intel" || Value == "att") {
+      CmdArgs.push_back(Args.MakeArgString("-mllvm"));
+      CmdArgs.push_back(Args.MakeArgString("-x86-asm-syntax=" + Value));
+    } else {
+      getToolChain().getDriver().Diag(diag::err_drv_unsupported_option_argument)
+          << A->getSpelling() << Value;
+    }
+  }
+}
+
 static void addVSDefines(const ToolChain &TC, const ArgList &Args,
                          ArgStringList &CmdArgs) {
 
@@ -374,6 +388,7 @@ void Flang::addTargetOptions(const ArgList &Args,
     break;
   case llvm::Triple::x86_64:
     getTargetFeatures(D, Triple, Args, CmdArgs, /*ForAs*/ false);
+    AddX86_64TargetArgs(Args, CmdArgs);
     break;
   }
 
diff --git a/clang/lib/Driver/ToolChains/Flang.h b/clang/lib/Driver/ToolChains/Flang.h
index ec2e545a1d0b5c..9f5e26b8608324 100644
--- a/clang/lib/Driver/ToolChains/Flang.h
+++ b/clang/lib/Driver/ToolChains/Flang.h
@@ -77,6 +77,13 @@ class LLVM_LIBRARY_VISIBILITY Flang : public Tool {
   void AddRISCVTargetArgs(const llvm::opt::ArgList &Args,
                           llvm::opt::ArgStringList &CmdArgs) const;
 
+  /// Add specific options for X86_64 target.
+  ///
+  /// \param [in] Args The list of input driver arguments
+  /// \param [out] CmdArgs The list of output command arguments
+  void AddX86_64TargetArgs(const llvm::opt::ArgList &Args,
+                           llvm::opt::ArgStringList &CmdArgs) const;
+
   /// Extract offload options from the driver arguments and add them to
   /// the command arguments.
   /// \param [in] C The current compilation for the driver invocation
diff --git a/flang/test/Driver/masm.f90 b/flang/test/Driver/masm.f90
new file mode 100644
index 00000000000000..a119f02787eca9
--- /dev/null
+++ b/flang/test/Driver/masm.f90
@@ -0,0 +1,13 @@
+// RUN: %flang -target x86_64-unknown-linux -masm=intel -S %s -### 2>&1 | FileCheck --check-prefix=CHECK-INTEL %s
+// RUN: %flang -target x86_64-unknown-linux -masm=att -S %s -### 2>&1 | FileCheck --check-prefix=CHECK-ATT %s
+// RUN: not %flang --target=x86_64-unknown-linux -S -masm=somerequired %s -### 2>&1 | FileCheck --check-prefix=CHECK-SOMEREQUIRED %s
+// RUN: %flang -target aarch64-unknown-eabi -S -masm=intel %s -### 2>&1 | FileCheck --check-prefix=CHECK-AARCH64 %s
+
+// CHECK-INTEL: "-mllvm" "-x86-asm-syntax=intel"
+// CHECK-ATT: "-mllvm" "-x86-asm-syntax=att"
+// CHECK-SOMEREQUIRED: error: unsupported argument 'somerequired' to option '-masm='
+// CHECK-AARCH64: warning: argument unused during compilation: '-masm=intel'
+// CHECK-AARCH64-NOT: -x86-asm-syntax=intel
+
+integer function fn()
+end function fn

[banach-space]

Nice, thank you!