Add clang patch to enable BFloat16 for SPIR/SPIR-V (#591)

Author: wenju-he

cmake/modules/CMakeFunctions.cmake

@@ -141,7 +141,7 @@ function(apply_patches repo_dir patches_dir base_revision target_branch)
                 message(STATUS "[OPENCL-CLANG] Not present - ${patching_log}")
             endif()
         endforeach(patch)
-    elsef(patches_needed EQUAL 0) # The target branch already exists
+    elseif(patches_needed EQUAL 0) # The target branch already exists
         execute_process( # Check it out
             COMMAND ${GIT_EXECUTABLE} checkout ${target_branch}
             WORKING_DIRECTORY ${repo_dir}

patches/clang/0001-Clang-Enable-BFloat16-for-SPIR-SPIR-V.patch

@@ -0,0 +1,36 @@
+From e3aa87e0aaad941c35709c8dc7a479b2a5251cfe Mon Sep 17 00:00:00 2001
+From: Wenju He <[email protected]>
+Date: Fri, 21 Nov 2025 05:43:57 +0100
+Subject: [PATCH] [Clang] Enable BFloat16 for SPIR/SPIR-V
+
+---
+ clang/lib/Basic/Targets/SPIR.h | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/clang/lib/Basic/Targets/SPIR.h b/clang/lib/Basic/Targets/SPIR.h
+index c0849b69dcdb..78a1c0e78107 100644
+--- a/clang/lib/Basic/Targets/SPIR.h
++++ b/clang/lib/Basic/Targets/SPIR.h
+@@ -103,6 +103,9 @@ protected:
+     UseAddrSpaceMapMangling = true;
+     HasLegalHalfType = true;
+     HasFloat16 = true;
++    HasBFloat16 = true;
++    BFloat16Width = BFloat16Align = 16;
++    BFloat16Format = &llvm::APFloat::BFloat();
+     // Define available target features
+     // These must be defined in sorted order!
+     NoAsmVariants = true;
+@@ -389,9 +392,6 @@ public:
+     resetDataLayout("e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-"
+                     "v256:256-v512:512-v1024:1024-n32:64-S32-G1-P4-A0");
+ 
+-    BFloat16Width = BFloat16Align = 16;
+-    BFloat16Format = &llvm::APFloat::BFloat();
+-
+     HasLegalHalfType = true;
+     HasFloat16 = true;
+     HalfArgsAndReturns = true;
+-- 
+2.39.1
+