From 860825ee14ab54c8b5ec1a1da0950387a6debd2a Mon Sep 17 00:00:00 2001
From: Robert Underwood <robertu94@users.noreply.github.com>
Date: Sat, 26 Dec 2020 10:47:37 -0500
Subject: llvm: provide fix for python dependencies (#20356)

Previously compiler-rt didn't correctly passthrough cmake
variables for python when building the various santizers.
This patch passes these variables through.

This patch may also correctly apply to any version of LLVM
to any version of LLVM that uses the newer monorepo style organization,
and any older llvm newer than 7.0.0 as long as the paths were set
appropriately.  However, this was not done so because it was not
tested with older LLVM releases.

Fixes #19908
See also: https://bugs.llvm.org/show_bug.cgi?id=48180
---
 .../repos/builtin/packages/llvm/llvm_python_path.patch     | 14 ++++++++++++++
 var/spack/repos/builtin/packages/llvm/package.py           | 14 +++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 var/spack/repos/builtin/packages/llvm/llvm_python_path.patch

diff --git a/var/spack/repos/builtin/packages/llvm/llvm_python_path.patch b/var/spack/repos/builtin/packages/llvm/llvm_python_path.patch
new file mode 100644
index 0000000000..9f821cc365
--- /dev/null
+++ b/var/spack/repos/builtin/packages/llvm/llvm_python_path.patch
@@ -0,0 +1,14 @@
+diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+index dab55707338..6f4c6791141 100644
+--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
++++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+@@ -612,6 +612,9 @@ macro(add_custom_libcxx name prefix)
+     CMAKE_OBJDUMP
+     CMAKE_STRIP
+     CMAKE_SYSROOT
++    PYTHON_EXECUTABLE
++    Python3_EXECUTABLE
++    Python2_EXECUTABLE
+     CMAKE_SYSTEM_NAME)
+   foreach(variable ${PASSTHROUGH_VARIABLES})
+     get_property(is_value_set CACHE ${variable} PROPERTY VALUE SET)
diff --git a/var/spack/repos/builtin/packages/llvm/package.py b/var/spack/repos/builtin/packages/llvm/package.py
index 6469f28c03..2f7b62707e 100644
--- a/var/spack/repos/builtin/packages/llvm/package.py
+++ b/var/spack/repos/builtin/packages/llvm/package.py
@@ -225,6 +225,10 @@ class Llvm(CMakePackage, CudaPackage):
     # merged in llvm-11.0.0_rc2
     patch("lldb_external_ncurses-10.patch", when="@10.0.0:10.99+lldb")
 
+    # https://github.com/spack/spack/issues/19908
+    # merged in llvm main prior to 12.0.0
+    patch("llvm_python_path.patch", when="@11.0.0")
+
     # The functions and attributes below implement external package
     # detection for LLVM. See:
     #
@@ -365,16 +369,24 @@ class Llvm(CMakePackage, CudaPackage):
 
     def cmake_args(self):
         spec = self.spec
+        python = spec['python']
         cmake_args = [
             "-DLLVM_REQUIRES_RTTI:BOOL=ON",
             "-DLLVM_ENABLE_RTTI:BOOL=ON",
             "-DLLVM_ENABLE_EH:BOOL=ON",
             "-DCLANG_DEFAULT_OPENMP_RUNTIME:STRING=libomp",
-            "-DPYTHON_EXECUTABLE:PATH={0}".format(spec["python"].command.path),
+            "-DPYTHON_EXECUTABLE:PATH={0}".format(python.command.path),
             "-DLIBOMP_USE_HWLOC:BOOL=ON",
             "-DLIBOMP_HWLOC_INSTALL_DIR={0}".format(spec["hwloc"].prefix),
         ]
 
+        if python.version >= Version("3.0.0"):
+            cmake_args.append("-DPython3_EXECUTABLE={0}".format(
+                              python.command.path))
+        else:
+            cmake_args.append("-DPython2_EXECUTABLE={0}".format(
+                              python.command.path))
+
         projects = []
 
         if "+cuda" in spec:
-- 
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