[all-commits] [llvm/llvm-project] 9ec748: [Flang] Search flang_rt in clang_rt path (#151954)

[Michael Kruse via All-commits]

  Branch: refs/heads/release/21.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 9ec748cfb155e69a3a38edaf68f0d3ea4c4ccf09
      https://github.com/llvm/llvm-project/commit/9ec748cfb155e69a3a38edaf68f0d3ea4c4ccf09
  Author: Michael Kruse <llvm-project at meinersbur.de>
  Date:   2025-08-08 (Fri, 08 Aug 2025)

  Changed paths:
    M clang/lib/Driver/ToolChain.cpp

  Log Message:
  -----------
  [Flang] Search flang_rt in clang_rt path (#151954)

The clang/flang driver has two separate systems for find the location of
clang_rt (simplified):

* `getCompilerRTPath()`, e.g. `../lib/clang/22/lib/windows`,
   used when `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=0`
* `getRuntimePath()`, e.g. `../lib/clang/22/lib/x86_64-pc-windows-msvc`,
   used when `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=1`

To simplify the search path, Flang-RT normally assumes only
`getRuntimePath()`, i.e. ignoring `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR`
and always using the `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=1` mechanism.
There is an exception for Apple Darwin triples where `getRuntimePath()`
returns nothing. The flang-rt/compiler-rt CMake code for library
location also ignores `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR` but uses the
`LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=0` path instead. Since only
`getRuntimePath()` is automatically added to the linker command line,
this patch explicitly adds `getCompilerRTPath()` to the path when
linking flang_rt.

Fixes #151031

(cherry picked from commit 8de481913353a1e37264687d5cc73db0de19e6cc)



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