Editorial: Inline IsSameBuffer with a simplified "same backing Data Block" check

cf. tc39#3629 (comment)

Author: gibson042

spec.html

@@ -42293,7 +42293,7 @@ <h1>
             1. Let _targetBuffer_ be _target_.[[ViewedArrayBuffer]].
             1. Let _srcBuffer_ be _source_.[[ViewedArrayBuffer]].
             1. Let _srcByteIndex_ be _source_.[[ByteOffset]].
-            1. If IsSameBuffer(_srcBuffer_, _targetBuffer_) is *true*, then
+            1. If _targetBuffer_.[[ArrayBufferData]] is _srcBuffer_.[[ArrayBufferData]], then
               1. NOTE: This operation must behave as if copying data into an overlapping range within the same Data Block is a single atomic step. But because the results of copying are not observable until it completes, implementations unable to perform such copying atomically may still avoid allocating a new ArrayBuffer by copying chunks in-place if they alter the direction of iteration as appropriate to avoid overwriting source data that has not yet been read.
               1. Let _srcByteLength_ be TypedArrayByteLength(_srcRecord_).
               1. Set _srcBuffer_ to ? CloneArrayBuffer(_srcBuffer_, _srcByteIndex_, _srcByteLength_).
@@ -44435,22 +44435,6 @@ <h1>
         </emu-alg>
       </emu-clause>
 
-      <emu-clause id="sec-issamebuffer" type="abstract operation">
-        <h1>
-          IsSameBuffer (
-            _a_: an ArrayBuffer or a SharedArrayBuffer,
-            _b_: an ArrayBuffer or a SharedArrayBuffer,
-          ): a Boolean
-        </h1>
-        <dl class="header">
-        </dl>
-        <emu-alg>
-          1. If SameValue(_a_, _b_) is *true*, return *true*.
-          1. If IsSharedArrayBuffer(_a_) is *true*, IsSharedArrayBuffer(_b_) is *true*, and _b_.[[ArrayBufferData]] is _a_.[[ArrayBufferData]], return *true*.
-          1. Return *false*.
-        </emu-alg>
-      </emu-clause>
-
       <emu-clause id="sec-getarraybuffermaxbytelengthoption" type="abstract operation">
         <h1>
           GetArrayBufferMaxByteLengthOption (
@@ -44942,7 +44926,7 @@ <h1>ArrayBuffer.prototype.slice ( _start_, _end_ )</h1>
           1. Perform ? RequireInternalSlot(_new_, [[ArrayBufferData]]).
           1. If IsSharedArrayBuffer(_new_) is *true*, throw a *TypeError* exception.
           1. If IsDetachedBuffer(_new_) is *true*, throw a *TypeError* exception.
-          1. If IsSameBuffer(_new_, _O_) is *true*, throw a *TypeError* exception.
+          1. If _new_.[[ArrayBufferData]] is _O_.[[ArrayBufferData]], throw a *TypeError* exception.
           1. If _new_.[[ArrayBufferByteLength]] &lt; _newLen_, throw a *TypeError* exception.
           1. NOTE: Side-effects of the above steps may have detached or resized _O_.
           1. If IsDetachedBuffer(_O_) is *true*, throw a *TypeError* exception.
@@ -45259,7 +45243,7 @@ <h1>SharedArrayBuffer.prototype.slice ( _start_, _end_ )</h1>
           1. Let _new_ be ? Construct(_ctor_, « 𝔽(_newLen_) »).
           1. Perform ? RequireInternalSlot(_new_, [[ArrayBufferData]]).
           1. If IsSharedArrayBuffer(_new_) is *false*, throw a *TypeError* exception.
-          1. If IsSameBuffer(_new_, _O_) is *true*, throw a *TypeError* exception.
+          1. If _new_.[[ArrayBufferData]] is _O_.[[ArrayBufferData]], throw a *TypeError* exception.
           1. If ArrayBufferByteLength(_new_, ~seq-cst~) &lt; _newLen_, throw a *TypeError* exception.
           1. Let _fromBuf_ be _O_.[[ArrayBufferData]].
           1. Let _toBuf_ be _new_.[[ArrayBufferData]].