From: Aman Gupta <redacted>
Date: Thu, 25 Dec 2025 14:12:11 +0000 (+0800)
Subject: ggml-cuda: fix blackwell native builds (llama/18361)
X-Git-Tag: v0.9.5~30
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=a5506cd13f278b2d20afc973e6d332a86a5df83c;p=pkg%2Fggml%2Fsources%2Fggml

ggml-cuda: fix blackwell native builds (llama/18361)

* ggml-cuda: fix blackwell native builds

Replace 12x in native architectures by 12xa

* replace for GGML_NATIVE=OFF too

* only replace for native

* remove 120f-virtual for default compilation

---------

Co-authored-by: Aman Gupta <aman>
---

diff --git a/src/ggml-cuda/CMakeLists.txt b/src/ggml-cuda/CMakeLists.txt
index f1412e8b..f3c3ebff 100644
--- a/src/ggml-cuda/CMakeLists.txt
+++ b/src/ggml-cuda/CMakeLists.txt
@@ -35,16 +35,33 @@ if (CUDAToolkit_FOUND)
             if (CUDAToolkit_VERSION VERSION_GREATER_EQUAL "11.8")
                 list(APPEND CMAKE_CUDA_ARCHITECTURES 89-real)
             endif()
-
-            if (CUDAToolkit_VERSION VERSION_GREATER_EQUAL "12.8")
-                list(APPEND CMAKE_CUDA_ARCHITECTURES 120f-virtual)
-            endif()
         endif()
     endif()
     message(STATUS "Using CUDA architectures: ${CMAKE_CUDA_ARCHITECTURES}")
 
     enable_language(CUDA)
 
+    # Replace any 12x-real architectures with 12x{a}-real. FP4 ptx instructions are not available in just 12x
+    if (GGML_NATIVE)
+        set(PROCESSED_ARCHITECTURES "")
+        foreach(ARCH ${CMAKE_CUDA_ARCHITECTURES_NATIVE})
+            if(ARCH MATCHES "^12[0-9]$")
+                string(REGEX REPLACE "^(12[0-9]).*$" "\\1" BASE_ARCH ${ARCH})
+                message(STATUS "Replacing ${ARCH} with ${BASE_ARCH}a-real")
+                list(APPEND PROCESSED_ARCHITECTURES "${BASE_ARCH}a-real")
+            else()
+                list(APPEND PROCESSED_ARCHITECTURES ${ARCH})
+            endif()
+        endforeach()
+        set(CMAKE_CUDA_ARCHITECTURES ${PROCESSED_ARCHITECTURES})
+    else()
+        foreach(ARCH ${CMAKE_CUDA_ARCHITECTURES})
+            if(ARCH MATCHES "^12[0-9]$")
+                message(FATAL_ERROR "Compute capability ${ARCH} used, use ${ARCH}a or ${ARCH}f for Blackwell specific optimizations")
+            endif()
+        endforeach()
+    endif()
+
     file(GLOB   GGML_HEADERS_CUDA "*.cuh")
     list(APPEND GGML_HEADERS_CUDA "../../include/ggml-cuda.h")