fix perf regression

mlx/backend/cuda/scaled_dot_product_attention.cu

@@ -463,7 +463,8 @@ void sdpa_vector_1pass_fallback(
     const array& v,
     const float scale,
     array& o,
-    bool do_causal_ = false) {
+    bool do_causal,
+    const std::optional<array>& sinks) {
   encoder.set_input_array(q);
   encoder.set_input_array(k);
   encoder.set_input_array(v);
@@ -489,7 +490,7 @@ void sdpa_vector_1pass_fallback(
   dim3 block_dim(1024, 1, 1);
 
   dispatch_float_types(o.dtype(), "kernel_sdpav_1pass", [&](auto type_tag) {
-    dispatch_bool(do_causal_, [&](auto do_causal) {
+    dispatch_bool(do_causal, [&](auto do_causal) {
       dispatch_headdim(params.D, [&](auto headdim) {
         using DataType = cuda_type_t<MLX_GET_TYPE(type_tag)>;
 
@@ -518,7 +519,8 @@ void sdpa_vector_2pass_fallback(
     const array& v,
     const float scale,
     array& o,
-    bool do_causal_ = false) {
+    bool do_causal,
+    const std::optional<array>& sinks) {
   cu::AttnParams params{
       /* int B = */ q.shape(0),
       /* int H = */ q.shape(1),
@@ -559,7 +561,7 @@ void sdpa_vector_2pass_fallback(
   encoder.add_temporary(maxs);
 
   dispatch_float_types(o.dtype(), "kernel_sdpav_2pass", [&](auto type_tag) {
-    dispatch_bool(do_causal_, [&](auto do_causal) {
+    dispatch_bool(do_causal, [&](auto do_causal) {
       dispatch_headdim(params.D, [&](auto headdim) {
         using DataType = cuda_type_t<MLX_GET_TYPE(type_tag)>;
 
@@ -627,15 +629,16 @@ void sdpa_vector_fallback(
     const array& v,
     const float scale,
     array& o,
-    bool do_causal_ = false) {
+    bool do_causal,
+    const std::optional<array>& sinks) {
   int kL = k.shape(2);
 
   if (kL > 1024) {
     return sdpa_vector_2pass_fallback(
-        s, encoder, q, k, v, scale, o, do_causal_);
+        s, encoder, q, k, v, scale, o, do_causal, sinks);
   } else {
     return sdpa_vector_1pass_fallback(
-        s, encoder, q, k, v, scale, o, do_causal_);
+        s, encoder, q, k, v, scale, o, do_causal, sinks);
   }
 }
 
@@ -703,6 +706,16 @@ void ScaledDotProductAttention::eval_gpu(
     }
   };
 
+  // Checks that the headdim dimension has stride 1.
+  auto is_matrix_contiguous = [](const array& arr) {
+    return arr.strides(-1) == 1;
+  };
+
+  std::optional<array> sinks = std::nullopt;
+  if (has_sinks_) {
+    sinks = copy_unless(is_matrix_contiguous, inputs.back());
+  }
+
   // We are in vector mode ie single query
   if (q_pre.shape(2) < 4) {
     auto q_copy_unless = [](const array& arr) {
@@ -766,7 +779,8 @@ void ScaledDotProductAttention::eval_gpu(
       encoder.add_temporary(cp);
     }
 
-    return sdpa_vector_fallback(s, encoder, q, k, v, scale_, o, do_causal_);
+    return sdpa_vector_fallback(
+        s, encoder, q, k, v, scale_, o, do_causal_, sinks);
   }
 
   // Full attention mode should never reach here

mlx/backend/metal/kernels/sdpa_vector.h

@@ -116,17 +116,15 @@ template <typename T, int D, int V = D>
         score += q[j] * k[j];
       }
       score = simd_sum(score);
-      if (score < Limits<T>::finite_min) {
-        continue;
-      }
       if (float_mask) {
         score += static_cast<U>(fmask[0]);
       }
 
       // Update the accumulators
       U new_max = max(max_score, score);
-      U factor = fast::exp(max_score - new_max);
-      U exp_score = fast::exp(score - new_max);
+      bool is_neg_inf = new_max == -INFINITY;
+      U factor = is_neg_inf ? 1.0 : fast::exp(max_score - new_max);
+      U exp_score = is_neg_inf ? 0.0 : fast::exp(score - new_max);
 
       max_score = new_max;
       sum_exp_score = sum_exp_score * factor + exp_score;