Correctly describe POPCNT compile

lucasart · zamar · commit d9caede32496 · 2014-11-01T20:43:57.000Z
SSE4.2 has nothing to do with POPCNT. We must dispell this myth, because Stockfish is a reference and many will copy this mistake if they see it in Stockfish: * SSE is an SIMD instruction set, relative to vectorization (using special 128-bit registers). * POPCNT/LZCNT work on normal registers (eg. AL, AX, EAX, RAX). The confusion comes from the fact that, in the Intel product line, it just so happens that SSE4.2 and POPCNT/LZCNT came out at the same time. But this is not true for AMD. For example, all AMD Pheniom II have SSE3 but no POPCNT/LZCNT, and that is why the modern compile uses -msse3 -popcnt and not -msse4.2. No functional change. Resolves #86
diff --git a/src/misc.cpp b/src/misc.cpp
@@ -115,7 +115,7 @@ const string engine_info(bool to_uci) {
   }
 
   ss << (Is64Bit ? " 64" : "")
-     << (HasPext ? " BMI2" : (HasPopCnt ? " SSE4.2" : ""))
+     << (HasPext ? " BMI2" : (HasPopCnt ? " POPCNT" : ""))
      << (to_uci  ? "\nid author ": " by ")
      << "Tord Romstad, Marco Costalba and Joona Kiiski";
 

Original file line number	Diff line number	Diff line change
`@@ -115,7 +115,7 @@ const string engine_info(bool to_uci) {`
`115`	`115`	`}`
`116`	`116`
`117`	`117`	`ss << (Is64Bit ? " 64" : "")`
`118`		`- << (HasPext ? " BMI2" : (HasPopCnt ? " SSE4.2" : ""))`
	`118`	`+ << (HasPext ? " BMI2" : (HasPopCnt ? " POPCNT" : ""))`
`119`	`119`	`<< (to_uci ? "\nid author ": " by ")`
`120`	`120`	`<< "Tord Romstad, Marco Costalba and Joona Kiiski";`
`121`	`121`