Specify GCC prefix in LLVM-based compilers (#33146)

* spack.compiler.Compiler: introduce prefix property

We currently don't really have something that gives the GCC install
path, which is used by many LLVM-based compilers (llvm, llvm-amdgpu,
nvhpc, ...) to fix the GCC toolchain once and for all.

This `prefix` property is dynamic in the sense that it queries the
compiler itself. This is necessary because it's not easy to deduce the
install path from the `cc` property (might be a symlink, might be a
filename like `gcc` which works by having the compiler load a module
that sets the PATH variable, might be a generic compiler wrapper based
on environment variables like on cray...).

With this property introduced, we can clean up some recipes that have
the logic repeated for GCC.

* intel-oneapi-compilers: set --gcc-sysroot to %gcc prefix

lib/spack/spack/compiler.py

@@ -537,6 +537,14 @@ def get_real_version(self):
             )
             return self.extract_version_from_output(output)
 
+    @property
+    def prefix(self):
+        """Query the compiler for its install prefix. This is the install
+        path as reported by the compiler. Note that paths for cc, cxx, etc
+        are not enough to find the install prefix of the compiler, since
+        the can be symlinks, wrappers, or filenames instead of absolute paths."""
+        raise NotImplementedError("prefix is not implemented for this compiler")
+
     #
     # Compiler classes have methods for querying the version of
     # specific compiler executables.  This is used when discovering compilers.

lib/spack/spack/compilers/gcc.py

@@ -6,8 +6,11 @@
 import os
 import re
 
+from llnl.util.filesystem import ancestor
+
 import spack.compiler
 import spack.compilers.apple_clang as apple_clang
+import spack.util.executable
 from spack.version import ver
 
 
@@ -196,3 +199,21 @@ def f77_version(cls, f77):
     @property
     def stdcxx_libs(self):
         return ("-lstdc++",)
+
+    @property
+    def prefix(self):
+        # GCC reports its install prefix when running ``-print-search-dirs``
+        # on the first line ``install: <prefix>``.
+        cc = spack.util.executable.Executable(self.cc)
+        with self.compiler_environment():
+            gcc_output = cc("-print-search-dirs", output=str, error=str)
+
+            for line in gcc_output.splitlines():
+                if line.startswith("install:"):
+                    gcc_prefix = line.split(":")[1].strip()
+                    # Go from <prefix>/lib/gcc/<triplet>/<version>/ to <prefix>
+                    return ancestor(gcc_prefix, 4)
+
+            raise RuntimeError(
+                "could not find install prefix of GCC from output:\n\t{}".format(gcc_output)
+            )

var/spack/repos/builtin/packages/intel-oneapi-compilers/package.py

@@ -5,6 +5,7 @@
 
 import platform
 
+import spack.compilers
 from spack.build_environment import dso_suffix
 from spack.package import *
 
@@ -113,6 +114,15 @@ class IntelOneapiCompilers(IntelOneApiPackage):
 
     depends_on("patchelf", type="build")
 
+    # TODO: effectively gcc is a direct dependency of intel-oneapi-compilers, but we
+    # cannot express that properly. For now, add conflicts for non-gcc compilers
+    # instead.
+    for __compiler in spack.compilers.supported_compilers():
+        if __compiler != "gcc":
+            conflicts(
+                "%{0}".format(__compiler), msg="intel-oneapi-compilers must be installed with %gcc"
+            )
+
     if platform.system() == "Linux":
         for v in linux_versions:
             version(v["version"], expand=False, **v["cpp"])
@@ -186,7 +196,9 @@ def extend_config_flags(self):
         # TODO: it is unclear whether we should really use all elements of
         #  _ld_library_path because it looks like the only rpath that needs to be
         #  injected is self.component_prefix.linux.compiler.lib.intel64_lin.
-        flags = " ".join(["-Wl,-rpath,{0}".format(d) for d in self._ld_library_path()])
+        flags_list = ["-Wl,-rpath,{}".format(d) for d in self._ld_library_path()]
+        flags_list.append("--gcc-toolchain={}".format(self.compiler.prefix))
+        flags = " ".join(flags_list)
         for cmp in [
             "icx",
             "icpx",

var/spack/repos/builtin/packages/llvm-amdgpu/package.py

@@ -234,18 +234,7 @@ def cmake_args(self):
 
         # Get the GCC prefix for LLVM.
         if self.compiler.name == "gcc":
-            compiler = Executable(self.compiler.cc)
+            args.append(self.define("GCC_INSTALL_PREFIX", self.compiler.prefix))
-            gcc_output = compiler("-print-search-dirs", output=str, error=str)
-
-            gcc_prefix = ""
-            for line in gcc_output.splitlines():
-                if line.startswith("install:"):
-                    # Get path and strip any whitespace
-                    # (causes oddity with ancestor)
-                    gcc_prefix = line.split(":")[1].strip()
-                    gcc_prefix = ancestor(gcc_prefix, 4)
-                    break
-            args.append(self.define("GCC_INSTALL_PREFIX", gcc_prefix))
 
         return args
 

var/spack/repos/builtin/packages/llvm-doe/package.py

@@ -582,17 +582,7 @@ def cmake_args(self):
                 cmake_args.append("-DLIBOMP_USE_ARGOBOTS=ON")
 
         if self.compiler.name == "gcc":
-            compiler = Executable(self.compiler.cc)
+            cmake_args.append(define("GCC_INSTALL_PREFIX", self.compiler.prefix))
-            gcc_output = compiler("-print-search-dirs", output=str, error=str)
-
-            for line in gcc_output.splitlines():
-                if line.startswith("install:"):
-                    # Get path and strip any whitespace
-                    # (causes oddity with ancestor)
-                    gcc_prefix = line.split(":")[1].strip()
-                    gcc_prefix = ancestor(gcc_prefix, 4)
-                    break
-            cmake_args.append(define("GCC_INSTALL_PREFIX", gcc_prefix))
 
         # if spec.satisfies("platform=cray") or spec.satisfies("platform=linux"):
         #     cmake_args.append("-DCMAKE_BUILD_WITH_INSTALL_RPATH=1")

var/spack/repos/builtin/packages/llvm/package.py

@@ -721,17 +721,7 @@ def cmake_args(self):
         cmake_args.append(from_variant("LIBOMP_TSAN_SUPPORT", "omp_tsan"))
 
         if self.compiler.name == "gcc":
-            compiler = Executable(self.compiler.cc)
+            cmake_args.append(define("GCC_INSTALL_PREFIX", self.compiler.prefix))
-            gcc_output = compiler("-print-search-dirs", output=str, error=str)
-
-            for line in gcc_output.splitlines():
-                if line.startswith("install:"):
-                    # Get path and strip any whitespace
-                    # (causes oddity with ancestor)
-                    gcc_prefix = line.split(":")[1].strip()
-                    gcc_prefix = ancestor(gcc_prefix, 4)
-                    break
-            cmake_args.append(define("GCC_INSTALL_PREFIX", gcc_prefix))
 
         if self.spec.satisfies("~code_signing platform=darwin"):
             cmake_args.append(define("LLDB_USE_SYSTEM_DEBUGSERVER", True))