From 4e9562ca7b4214fe359b5f3b885443e301bc5f74 Mon Sep 17 00:00:00 2001
From: Michael Wilson <mjwilson@chromium.org>
Date: Tue, 10 Mar 2026 10:08:27 -0700
Subject: [PATCH] Replace UNSAFE_BUFFERS in AudioParamHandler with safe operations

This should cause no functional change.

Also do a small optimization in HandleNaNValues for inputs that are
larger than 4 by skipping the first if check, since we expect longer
inputs in general.

Bug: 401184803
Bug: 490642831
Change-Id: I1044267b7e6370af4793fe973fe36224630ced95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7649387
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Michael Wilson <mjwilson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1597152}
---

diff --git a/third_party/blink/renderer/modules/webaudio/audio_param_handler.cc b/third_party/blink/renderer/modules/webaudio/audio_param_handler.cc
index b3b95dd..88a8f39 100644
--- a/third_party/blink/renderer/modules/webaudio/audio_param_handler.cc
+++ b/third_party/blink/renderer/modules/webaudio/audio_param_handler.cc
@@ -51,40 +51,35 @@
 void HandleNaNValues(base::span<float> values, float default_value) {
   unsigned k = 0;
 #if defined(ARCH_CPU_X86_FAMILY)
-  if (values.size() >= 4) {
-    __m128 defaults = _mm_set1_ps(default_value);
-    for (k = 0; k < values.size(); k += 4) {
-      // SAFETY: The for loop condition has been checked k < values.size().
-      __m128 v = _mm_loadu_ps(UNSAFE_BUFFERS(values.data() + k));
-      // cmpuord returns all 1's if v is NaN for each elmeent of v.
-      __m128 isnan = _mm_cmpunord_ps(v, v);
-      // Replace NaN parts with default.
-      __m128 result = _mm_and_ps(isnan, defaults);
-      // Merge in the parts that aren't NaN
-      result = _mm_or_ps(_mm_andnot_ps(isnan, v), result);
-      // SAFETY: The for loop condition has been checked k < values.size().
-      _mm_storeu_ps(UNSAFE_BUFFERS(values.data() + k), result);
-    }
+  // Truncate to the next-lowest multiple of 4.
+  const size_t truncated_size = values.size() & ~3;
+  __m128 defaults = _mm_set1_ps(default_value);
+  for (k = 0; k < truncated_size; k += 4) {
+    __m128 v = _mm_loadu_ps(values.subspan(k, 4u).data());
+    // cmpuord returns all 1's if v is NaN for each elmeent of v.
+    __m128 isnan = _mm_cmpunord_ps(v, v);
+    // Replace NaN parts with default.
+    __m128 result = _mm_and_ps(isnan, defaults);
+    // Merge in the parts that aren't NaN
+    result = _mm_or_ps(_mm_andnot_ps(isnan, v), result);
+    _mm_storeu_ps(values.subspan(k, 4u).data(), result);
   }
 #elif defined(CPU_ARM_NEON)
-  if (values.size() >= 4) {
-    uint32x4_t defaults =
-        reinterpret_cast<uint32x4_t>(vdupq_n_f32(default_value));
-    for (k = 0; k < values.size(); k += 4) {
-      // SAFETY: The for loop condition has been checked k < values.size().
-      float32x4_t v = vld1q_f32(UNSAFE_BUFFERS(values.data() + k));
-      // Returns true (all ones) if v is not NaN
-      uint32x4_t is_not_nan = vceqq_f32(v, v);
-      // Get the parts that are not NaN
-      uint32x4_t result =
-          vandq_u32(is_not_nan, reinterpret_cast<uint32x4_t>(v));
-      // Replace the parts that are NaN with the default and merge with previous
-      // result.  (Note: vbic_u32(x, y) = x and not y)
-      result = vorrq_u32(result, vbicq_u32(defaults, is_not_nan));
-      // SAFETY: The for loop condition has been checked k < values.size().
-      vst1q_f32(UNSAFE_BUFFERS(values.data() + k),
-                reinterpret_cast<float32x4_t>(result));
-    }
+  // Truncate to the next-lowest multiple of 4.
+  const size_t truncated_size = values.size() & ~3;
+  uint32x4_t defaults =
+      reinterpret_cast<uint32x4_t>(vdupq_n_f32(default_value));
+  for (k = 0; k < truncated_size; k += 4) {
+    float32x4_t v = vld1q_f32(values.subspan(k, 4u).data());
+    // Returns true (all ones) if v is not NaN
+    uint32x4_t is_not_nan = vceqq_f32(v, v);
+    // Get the parts that are not NaN
+    uint32x4_t result = vandq_u32(is_not_nan, reinterpret_cast<uint32x4_t>(v));
+    // Replace the parts that are NaN with the default and merge with previous
+    // result.  (Note: vbic_u32(x, y) = x and not y)
+    result = vorrq_u32(result, vbicq_u32(defaults, is_not_nan));
+    vst1q_f32(values.subspan(k, 4u).data(),
+              reinterpret_cast<float32x4_t>(result));
   }
 #endif
 
@@ -1831,10 +1826,7 @@
 
     // Process 4 loop steps.
     for (; write_index < fill_to_frame_trunc; write_index += 4) {
-      // SAFETY: DCHECK previously checked that `fill_to_frame_trunc <
-      // values.size()`. In the for loop, `write_index < fill_to_frame_trunc` so
-      // this is safe.
-      _mm_storeu_ps(UNSAFE_BUFFERS(values.data() + write_index), v_value);
+      _mm_storeu_ps(values.subspan(write_index, 4u).data(), v_value);
       v_value = _mm_add_ps(v_value, v_inc);
     }
   }
@@ -2020,10 +2012,7 @@
         v_value = _mm_set_ps1(value);
 
         v_result = _mm_add_ps(v_value, _mm_mul_ps(v_delta, v_c));
-        // SAFETY: DCHECK previously checked that `fill_to_frame_trunc <
-        // values.size()`. In the for loop, `write_index < fill_to_frame_trunc`
-        // so this is safe.
-        _mm_storeu_ps(UNSAFE_BUFFERS(values.data() + write_index), v_result);
+        _mm_storeu_ps(values.subspan(write_index, 4u).data(), v_result);
 
         // Update value for next iteration.
         value += delta * c3;
@@ -2184,10 +2173,7 @@
       __m128 v_value =
           _mm_add_ps(v_c0, _mm_mul_ps(_mm_sub_ps(v_c1, v_c0), v_delta));
 
-      // SAFETY: DCHECK previously checked that `fill_to_frame_trunc <
-      // values.size()`. In the for loop, `write_index < fill_to_frame_trunc` so
-      // this is safe.
-      _mm_storeu_ps(UNSAFE_BUFFERS(values.data() + write_index), v_value);
+      _mm_storeu_ps(values.subspan(write_index, 4u).data(), v_value);
     }
     // Pass along k to the serial loop.
     k = truncated_steps;