diff --git a/llvm/lib/Support/BLAKE3/CMakeLists.txt b/llvm/lib/Support/BLAKE3/CMakeLists.txt
index 615665becf41..718dd6421648 100644
--- a/llvm/lib/Support/BLAKE3/CMakeLists.txt
+++ b/llvm/lib/Support/BLAKE3/CMakeLists.txt
@@ -4,21 +4,6 @@ set(LLVM_BLAKE3_FILES
   blake3_portable.c
 )
 
-set(CAN_USE_ASSEMBLER TRUE)
-# Some LLVM builders set "CC=ccache /path/to/clang" as environment variable,
-# which confuses CMake thinking the assembler to use is the 'ccache' binary.
-# These builders need to also set "ASM=/path/to/clang" in environment, but until
-# this happens check for this case and disable building the assembly files.
-get_filename_component(ASM_BINARY ${CMAKE_ASM_COMPILER} NAME)
-if (ASM_BINARY STREQUAL "ccache")
-  message(WARNING "CMake is set to use '${CMAKE_ASM_COMPILER}' as assembler "
-    "which is likely due to having 'CC=ccache /path/to/clang' in the environment. "
-    "Building the BLAKE3 SIMD-optimized assembly files is disabled, set "
-    "'ASM=/path/to/clang' as environment variable and do a clean re-configure "
-    "to correct this.")
-  set(CAN_USE_ASSEMBLER FALSE)
-endif()
-
 # The BLAKE3 team recommends using the assembly versions, from the README:
 #
 # "For each of the x86 SIMD instruction sets, four versions are available:
@@ -26,18 +11,13 @@ endif()
 # version using C intrinsics. The assembly versions are generally
 # preferred. They perform better, they perform more consistently across
 # different compilers, and they build more quickly."
-
+# FIXME: Figure out what is wrong with the builders when using the assembly files and neon.
 if (MSVC)
-  check_symbol_exists(_M_X64 "" IS_X64)
-  check_symbol_exists(_M_ARM64 "" IS_ARM64)
-else()
-  check_symbol_exists(__x86_64__ "" IS_X64)
-  check_symbol_exists(__aarch64__ "" IS_ARM64)
+  enable_language(ASM_MASM)
 endif()
 
-if (IS_X64 AND CAN_USE_ASSEMBLER)
+if (FALSE)#CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64)$")
   if (MSVC)
-    enable_language(ASM_MASM)
     list(APPEND LLVM_BLAKE3_FILES
       blake3_sse2_x86-64_windows_msvc.asm
       blake3_sse41_x86-64_windows_msvc.asm
@@ -61,15 +41,14 @@ if (IS_X64 AND CAN_USE_ASSEMBLER)
   endif()
 endif()
 
-if (IS_ARM64)
+if (FALSE)#CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm|aarch)")
   list(APPEND LLVM_BLAKE3_FILES
     blake3_neon.c
   )
 endif()
 
-if (IS_X64 AND NOT CAN_USE_ASSEMBLER)
-  add_definitions(-DBLAKE3_NO_AVX512 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_SSE41 -DBLAKE3_NO_SSE2)
-endif()
+# FIXME: Figure out what is wrong with the builders when using the assembly files.
+add_definitions(-DBLAKE3_NO_AVX512 -DBLAKE3_NO_AVX2 -DBLAKE3_NO_SSE41 -DBLAKE3_NO_SSE2 -DBLAKE3_USE_NEON=0)
 
 add_library(LLVMSupportBlake3 OBJECT EXCLUDE_FROM_ALL ${LLVM_BLAKE3_FILES})
 llvm_update_compile_flags(LLVMSupportBlake3)