diff --git a/0001-PATCH-llvm-Make-source-interleave-prefix-test-case-c.patch b/0001-PATCH-llvm-Make-source-interleave-prefix-test-case-c.patch
new file mode 100644
index 0000000..1f423e9
--- /dev/null
+++ b/0001-PATCH-llvm-Make-source-interleave-prefix-test-case-c.patch
@@ -0,0 +1,29 @@
+From ff206863a626dad99d011aeb60770270c300e56f Mon Sep 17 00:00:00 2001
+From: Konrad Kleine <kkleine@redhat.com>
+Date: Tue, 27 Apr 2021 14:41:57 +0200
+Subject: [PATCH] [PATCH][llvm] Make source-interleave-prefix test case
+ compatible with llvm-test
+
+llvm-test runs test from a directory that's not the upstream one, and that leads
+to some false positive. Workaround this by forcing the current working
+directory.
+---
+ llvm/test/tools/llvm-objdump/X86/source-interleave-prefix.test | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/llvm/test/tools/llvm-objdump/X86/source-interleave-prefix.test b/llvm/test/tools/llvm-objdump/X86/source-interleave-prefix.test
+index 746add22f96e..8b28b877e372 100644
+--- a/llvm/test/tools/llvm-objdump/X86/source-interleave-prefix.test
++++ b/llvm/test/tools/llvm-objdump/X86/source-interleave-prefix.test
+@@ -11,7 +11,7 @@
+ 
+ ; RUN: sed -e "s,SRC_COMPDIR,./Inputs,g" %p/Inputs/source-interleave.ll > %t-relative-path.ll
+ ; RUN: llc -o %t-relative-path.o -filetype=obj -mtriple=x86_64-pc-linux %t-relative-path.ll
+-; RUN: llvm-objdump --prefix myprefix --source %t-relative-path.o 2>&1 | \
++; RUN: mkdir -p %t0 && cd %t0 && llvm-objdump --prefix myprefix --source %t-relative-path.o 2>&1 | \
+ ; RUN:   FileCheck %s --check-prefix=CHECK-BROKEN-PREFIX -DFILE=%t-relative-path.o -DPREFIX=. -DCOMPDIR=/Inputs
+ ; CHECK-BROKEN-PREFIX: warning: '[[FILE]]': failed to find source [[PREFIX]][[COMPDIR]]{{[/\\]}}source-interleave-x86_64.c
+ 
+-- 
+2.31.1
+
diff --git a/llvm.spec b/llvm.spec
index f3f8a70..3519181 100644
--- a/llvm.spec
+++ b/llvm.spec
@@ -50,6 +50,19 @@
 %global cmake_srcdir cmake-%{maj_ver}.%{min_ver}.%{patch_ver}%{?rc_ver:rc%{rc_ver}}.src
 %global third_party_srcdir third-party-%{maj_ver}.%{min_ver}.%{patch_ver}%{?rc_ver:rc%{rc_ver}}.src
 
+%if %{with snapshot_build}
+%undefine rc_ver
+%global llvm_snapshot_vers pre%{llvm_snapshot_yyyymmdd}.g%{llvm_snapshot_git_revision_short}
+# FIXME(kkleine): Until we have the top-level "cmake" directory of the LLVM
+# source tree separated out, we're going to use the complete source tarball
+# ("llvm-project" instead of "llvm") for this.
+%global llvm_srcdir llvm-project-%{llvm_snapshot_version_major}.%{llvm_snapshot_version_minor}.%{llvm_snapshot_version_patch}.src/llvm
+%global maj_ver %{llvm_snapshot_version_major}
+%global min_ver %{llvm_snapshot_version_minor}
+%global patch_ver %{llvm_snapshot_version_patch}
+%endif
+
+
 %if %{with compat_build}
 %global pkg_name llvm%{maj_ver}
 %global exec_suffix -%{maj_ver}
@@ -200,6 +213,12 @@ Requires(postun): /sbin/ldconfig
 %description libs
 Shared libraries for the LLVM compiler infrastructure.
 
+%package cmake-devel
+Summary:	LLVM Shared development CMake files
+
+%description cmake-devel
+Some CMake files that are shared by LLVM sub-projects when building.
+
 %package static
 Summary:	LLVM static libraries
 Conflicts:	%{name}-devel < 8