add flag to disable FP16 compile

csrc/flash_api.cpp

@@ -77,7 +77,6 @@ mha_fwd_kvcache_mla(
     at::Tensor vcache = vcache_.has_value() ? vcache_.value() : kcache;
 
     auto q_dtype = q.dtype();
-    TORCH_CHECK(q_dtype == torch::kBFloat16 || q_dtype == torch::kFloat16);
     TORCH_CHECK(kcache.dtype() == q_dtype, "query and key must have the same dtype");
 
     CHECK_DEVICE(q); CHECK_DEVICE(kcache); CHECK_DEVICE(vcache);
@@ -189,9 +188,15 @@ mha_fwd_kvcache_mla(
 
     if (q_dtype == torch::kBFloat16) {
         run_mha_fwd_splitkv_mla<cutlass::bfloat16_t, 576>(params, stream);
-    } else {
+    }
+    #ifndef FLASH_MLA_DISABLE_FP16
+    else if (q_dtype == torch::kHalf) {
         run_mha_fwd_splitkv_mla<cutlass::half_t, 576>(params, stream);
     }
+    #endif
+    else {
+        TORCH_CHECK(false, "Unsupported tensor dtype for query");
+    }
 
     out = out.view({batch_size, seqlen_q_ori, ngroups, num_heads_k, head_size_v}).transpose(2, 3)
             .reshape({batch_size, seqlen_q_ori, num_heads_ori, head_size_v});

setup.py

@@ -11,11 +11,29 @@ from torch.utils.cpp_extension import (
     IS_WINDOWS,
 )
 
+DISABLE_FP16 = os.getenv("FLASH_MLA_DISABLE_FP16", "FALSE") == "TRUE"
 
 def append_nvcc_threads(nvcc_extra_args):
     nvcc_threads = os.getenv("NVCC_THREADS") or "32"
     return nvcc_extra_args + ["--threads", nvcc_threads]
 
+def get_sources():
+    sources = [
+        "csrc/flash_api.cpp",
+        "csrc/flash_fwd_mla_bf16_sm90.cu",
+        "csrc/flash_fwd_mla_metadata.cu",
+    ]
+
+    if not DISABLE_FP16:
+        sources.append("csrc/flash_fwd_mla_fp16_sm90.cu")
+
+    return sources
+
+def get_features_args():
+    features_args = []
+    if DISABLE_FP16:
+        features_args.append("-DFLASH_MLA_DISABLE_FP16")
+    return features_args
 
 subprocess.run(["git", "submodule", "update", "--init", "csrc/cutlass"])
 
@@ -34,14 +52,9 @@ ext_modules = []
 ext_modules.append(
     CUDAExtension(
         name="flash_mla_cuda",
-        sources=[
-            "csrc/flash_api.cpp",
-            "csrc/flash_fwd_mla_bf16_sm90.cu",
-            "csrc/flash_fwd_mla_fp16_sm90.cu",
-            "csrc/flash_fwd_mla_metadata.cu",
-        ],
+        sources=get_sources(),
         extra_compile_args={
-            "cxx": cxx_args,
+            "cxx": cxx_args + get_features_args(),
             "nvcc": append_nvcc_threads(
                 [
                     "-O3",
@@ -59,7 +72,7 @@ ext_modules.append(
                     "--ptxas-options=-v,--register-usage-level=10"
                 ]
                 + cc_flag
-            ),
+            ) + get_features_args(),
         },
         include_dirs=[
             Path(this_dir) / "csrc",