diff --git a/pkgs/development/compilers/llvm/20/llvm/gnu-install-dirs-polly.patch b/pkgs/development/compilers/llvm/20/llvm/gnu-install-dirs-polly.patch
new file mode 100644
index 000000000000..dfe21f9dcae0
--- /dev/null
+++ b/pkgs/development/compilers/llvm/20/llvm/gnu-install-dirs-polly.patch
@@ -0,0 +1,13 @@
+--- a/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:36:20.550893344 -0700
++++ b/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:37:06.277332960 -0700
+@@ -45,8 +45,8 @@
+     install(TARGETS ${name}
+       COMPONENT ${name}
+       ${exports}
+-      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX})
++      LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}
++      ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+     add_llvm_install_targets(install-${name}
+       COMPONENT ${name})
+   endif()
diff --git a/pkgs/development/compilers/llvm/common/default.nix b/pkgs/development/compilers/llvm/common/default.nix
index 7d2ef2e3f135..0fee6ce58ede 100644
--- a/pkgs/development/compilers/llvm/common/default.nix
+++ b/pkgs/development/compilers/llvm/common/default.nix
@@ -130,6 +130,11 @@ let
               ];
               "llvm/gnu-install-dirs-polly.patch" = [
                 {
+                  after = "20";
+                  path = ../20;
+                }
+                {
+                  before = "20";
                   after = "18";
                   path = ../18;
                 }
@@ -519,7 +524,8 @@ let
             (metadata.getVersionFile "clang/purity.patch")
             # https://reviews.llvm.org/D51899
             (metadata.getVersionFile "clang/gnu-install-dirs.patch")
-
+          ]
+          ++ lib.optionals (lib.versionOlder metadata.release_version "20") [
             # https://github.com/llvm/llvm-project/pull/116476
             # prevent clang ignoring warnings / errors for unsuppored
             # options when building & linking a source file with trailing
@@ -1063,7 +1069,7 @@ let
         ++ lib.optionals (lib.versionAtLeast metadata.release_version "13") [
           (metadata.getVersionFile "compiler-rt/armv6-scudo-libatomic.patch")
         ]
-        ++ lib.optional (lib.versionAtLeast metadata.release_version "19") (fetchpatch {
+        ++ lib.optional (lib.versions.major metadata.release_version == "19") (fetchpatch {
           url = "https://github.com/llvm/llvm-project/pull/99837/commits/14ae0a660a38e1feb151928a14f35ff0f4487351.patch";
           hash = "sha256-JykABCaNNhYhZQxCvKiBn54DZ5ZguksgCHnpdwWF2no=";
           relative = "compiler-rt";
diff --git a/pkgs/development/compilers/llvm/default.nix b/pkgs/development/compilers/llvm/default.nix
index ee60db1e08a6..6ff44ffecff2 100644
--- a/pkgs/development/compilers/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/default.nix
@@ -31,9 +31,9 @@ let
     "18.1.8".officialRelease.sha256 = "sha256-iiZKMRo/WxJaBXct9GdAcAT3cz9d9pnAcO1mmR6oPNE=";
     "19.1.6".officialRelease.sha256 = "sha256-LD4nIjZTSZJtbgW6tZopbTF5Mq0Tenj2gbuPXhtOeUI=";
     "20.0.0-git".gitRelease = {
-      rev = "1ef5b987a464611a60e873650726b5e02fda0feb";
-      rev-version = "20.0.0-unstable-2024-12-17";
-      sha256 = "sha256-QCY9z9h3z5gPvwq6bNzAB5xFFStwOCfKh4VnWInhxU4=";
+      rev = "6383a12e3b4339fa4743bb97da4d51dea6d2e2ea";
+      rev-version = "20.0.0-unstable-2025-01-25";
+      sha256 = "sha256-LMew+lFm+HrR5iwFDnoXA6B2LiU/pVqsy1YrP9xr5GU=";
     };
   } // llvmVersions;