[flang-commits] [flang] [flang] Updating drivers to create data layout before semantics (PR #73301)

[Andrzej Warzyński via flang-commits]

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@@ -0,0 +1,63 @@
+//===-- Tools/TargetSetup.h ------------------------------------- *-C++-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_TOOLS_TARGET_SETUP_H
+#define FORTRAN_TOOLS_TARGET_SETUP_H
+
+#include "flang/Evaluate/target.h"
+#include "llvm/MC/TargetRegistry.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/TargetParser/Host.h"
+#include <memory>
+
+namespace Fortran::tools {
+
+[[maybe_unused]] inline static void setUpTargetCharacteristics(
+    Fortran::evaluate::TargetCharacteristics &targetCharacteristics,
+    const llvm::TargetMachine &targetMachine,
+    const std::string &compilerVersion, const std::string &compilerOptions) {
+
+  const llvm::Triple &targetTriple{targetMachine.getTargetTriple()};
+  // FIXME: Handle real(3) ?
+  if (targetTriple.getArch() != llvm::Triple::ArchType::x86_64)
+    targetCharacteristics.DisableType(
+        Fortran::common::TypeCategory::Real, /*kind=*/10);
+
+  targetCharacteristics.set_compilerOptionsString(compilerOptions)
+      .set_compilerVersionString(compilerVersion);
+
+  if (targetTriple.isPPC())
+    targetCharacteristics.set_isPPC(true);
+
+  // TODO: use target machine data layout to set-up the target characteristics
+  // type size and alignment info.
+}
+
+/// Create a target machine that is at least sufficient to get data-layout
+/// information required by flang semantics and lowering. Note that it may not
+/// contain all the CPU feature information to get optimized assembly generation
+/// from LLVM IR. Drivers that needs to generate assembly from LLVM IR should
+/// create a target machine according to their specific options.
+[[maybe_unused]] inline static std::unique_ptr<llvm::TargetMachine>
+createTargetMachine(llvm::StringRef targetTriple, std::string &error) {
+  std::string triple{targetTriple};
+  if (triple.empty())
+    triple = llvm::sys::getDefaultTargetTriple();
+
+  const llvm::Target *theTarget =
+      llvm::TargetRegistry::lookupTarget(triple, error);
+  if (!theTarget)
+    return nullptr;
+  return std::unique_ptr<llvm::TargetMachine>{
+      theTarget->createTargetMachine(triple, /*CPU=*/"",
+          /*Features=*/"", llvm::TargetOptions(),
+          /*Reloc::Model=*/std::nullopt)};
+}
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banach-space wrote:

Given: https://github.com/llvm/llvm-project/blob/9ba74c2ee044381544c8e1e736c4c85a1a9d56bf/llvm/include/llvm/MC/TargetRegistry.h#L484-L500

this method shouldn't really be called `createTargetMachine` (to avoid confusion). If a specialisation of the original method is required, then IMHO it should live in LLVM. 

Also, from what I can see this is only needed by `bbc`, so I suggest moving it there. "Tools" based on LLVM Flang can leverage the APIs exposed by the driver logic that will handle this sort of configuration automatically.

https://github.com/llvm/llvm-project/pull/73301