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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/284850">284850</a></dd>
<dt>Author</dt> <dd>ysuzuki@apple.com</dd>
<dt>Date</dt> <dd>2021-10-25 17:16:10 -0700 (Mon, 25 Oct 2021)</dd>
</dl>
<h3>Log Message</h3>
<pre>[WTF] Make Int128 operator* constexpr
https://bugs.webkit.org/show_bug.cgi?id=232270
Reviewed by Mark Lam.
We remove MSVC X64 (so, Windows only) switching in Int128 operator* since
it breaks constexpr-ness of operator*, which makes writing code difficult.
We can bring this kind of optimization back when C++20 std::is_constant_evaluated()
becomes available.
* wtf/Int128.h:
(WTF::operator*):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWTFChangeLog">trunk/Source/WTF/ChangeLog</a></li>
<li><a href="#trunkSourceWTFwtfInt128h">trunk/Source/WTF/wtf/Int128.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWTFChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/ChangeLog (284849 => 284850)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/ChangeLog 2021-10-25 23:41:45 UTC (rev 284849)
+++ trunk/Source/WTF/ChangeLog 2021-10-26 00:16:10 UTC (rev 284850)
</span><span class="lines">@@ -1,3 +1,18 @@
</span><ins>+2021-10-25 Yusuke Suzuki <ysuzuki@apple.com>
+
+ [WTF] Make Int128 operator* constexpr
+ https://bugs.webkit.org/show_bug.cgi?id=232270
+
+ Reviewed by Mark Lam.
+
+ We remove MSVC X64 (so, Windows only) switching in Int128 operator* since
+ it breaks constexpr-ness of operator*, which makes writing code difficult.
+ We can bring this kind of optimization back when C++20 std::is_constant_evaluated()
+ becomes available.
+
+ * wtf/Int128.h:
+ (WTF::operator*):
+
</ins><span class="cx"> 2021-10-25 Alex Christensen <achristensen@webkit.org>
</span><span class="cx">
</span><span class="cx"> Use xpc_connection_copy_invalidation_reason where available for debugging daemon connection failures
</span></span></pre></div>
<a id="trunkSourceWTFwtfInt128h"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/wtf/Int128.h (284849 => 284850)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/wtf/Int128.h 2021-10-25 23:41:45 UTC (rev 284849)
+++ trunk/Source/WTF/wtf/Int128.h 2021-10-26 00:16:10 UTC (rev 284850)
</span><span class="lines">@@ -48,13 +48,9 @@
</span><span class="cx"> // builtin type. We need to make sure not to define operator wchar_t()
</span><span class="cx"> // alongside operator unsigned short() in these instances.
</span><span class="cx"> #define ABSL_INTERNAL_WCHAR_T __wchar_t
</span><del>-#if CPU(X86_64)
-#include <intrin.h>
-#pragma intrinsic(_umul128)
-#endif // defined(_M_X64)
-#else // defined(_MSC_VER)
</del><ins>+#else
</ins><span class="cx"> #define ABSL_INTERNAL_WCHAR_T wchar_t
</span><del>-#endif // defined(_MSC_VER)
</del><ins>+#endif
</ins><span class="cx">
</span><span class="cx"> namespace WTF {
</span><span class="cx">
</span><span class="lines">@@ -515,7 +511,7 @@
</span><span class="cx"> constexpr UInt128Impl operator>>(UInt128Impl lhs, int amount);
</span><span class="cx"> constexpr UInt128Impl operator+(UInt128Impl lhs, UInt128Impl rhs);
</span><span class="cx"> constexpr UInt128Impl operator-(UInt128Impl lhs, UInt128Impl rhs);
</span><del>-UInt128Impl operator*(UInt128Impl lhs, UInt128Impl rhs);
</del><ins>+constexpr UInt128Impl operator*(UInt128Impl lhs, UInt128Impl rhs);
</ins><span class="cx"> WTF_EXPORT_PRIVATE UInt128Impl operator/(UInt128Impl lhs, UInt128Impl rhs);
</span><span class="cx"> WTF_EXPORT_PRIVATE UInt128Impl operator%(UInt128Impl lhs, UInt128Impl rhs);
</span><span class="cx">
</span><span class="lines">@@ -812,14 +808,7 @@
</span><span class="cx"> lhs, rhs);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-inline UInt128Impl operator*(UInt128Impl lhs, UInt128Impl rhs) {
-#if COMPILER(MSVC) && CPU(X86_64)
- uint64_t carry;
- uint64_t low = _umul128(UInt128Low64(lhs), UInt128Low64(rhs), &carry);
- return MakeUInt128(UInt128Low64(lhs) * UInt128High64(rhs) +
- UInt128High64(lhs) * UInt128Low64(rhs) + carry,
- low);
-#else
</del><ins>+constexpr UInt128Impl operator*(UInt128Impl lhs, UInt128Impl rhs) {
</ins><span class="cx"> uint64_t a32 = UInt128Low64(lhs) >> 32;
</span><span class="cx"> uint64_t a00 = UInt128Low64(lhs) & 0xffffffff;
</span><span class="cx"> uint64_t b32 = UInt128Low64(rhs) >> 32;
</span><span class="lines">@@ -828,10 +817,9 @@
</span><span class="cx"> MakeUInt128(UInt128High64(lhs) * UInt128Low64(rhs) +
</span><span class="cx"> UInt128Low64(lhs) * UInt128High64(rhs) + a32 * b32,
</span><span class="cx"> a00 * b00);
</span><del>- result += UInt128Impl(a32 * b00) << 32;
- result += UInt128Impl(a00 * b32) << 32;
- return result;
-#endif
</del><ins>+ UInt128Impl v1 = UInt128Impl(a32 * b00) << 32;
+ UInt128Impl v2 = UInt128Impl(a00 * b32) << 32;
+ return result + v1 + v2;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> // Increment/decrement operators.
</span><span class="lines">@@ -894,7 +882,7 @@
</span><span class="cx"> constexpr Int128Impl operator-(Int128Impl v);
</span><span class="cx"> constexpr Int128Impl operator+(Int128Impl lhs, Int128Impl rhs);
</span><span class="cx"> constexpr Int128Impl operator-(Int128Impl lhs, Int128Impl rhs);
</span><del>-Int128Impl operator*(Int128Impl lhs, Int128Impl rhs);
</del><ins>+constexpr Int128Impl operator*(Int128Impl lhs, Int128Impl rhs);
</ins><span class="cx"> WTF_EXPORT_PRIVATE Int128Impl operator/(Int128Impl lhs, Int128Impl rhs);
</span><span class="cx"> WTF_EXPORT_PRIVATE Int128Impl operator%(Int128Impl lhs, Int128Impl rhs);
</span><span class="cx"> constexpr Int128Impl operator|(Int128Impl lhs, Int128Impl rhs);
</span><span class="lines">@@ -1192,7 +1180,7 @@
</span><span class="cx"> lhs, rhs);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-inline Int128Impl operator*(Int128Impl lhs, Int128Impl rhs) {
</del><ins>+constexpr Int128Impl operator*(Int128Impl lhs, Int128Impl rhs) {
</ins><span class="cx"> return MakeInt128(
</span><span class="cx"> int128_internal::BitCastToSigned(UInt128High64(UInt128Impl(lhs) * rhs)),
</span><span class="cx"> UInt128Low64(UInt128Impl(lhs) * rhs));
</span></span></pre>
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