Make benign truncation checks apply more broadly to sign-extended move chains.

SMPInstr.cpp

@@ -4544,24 +4544,22 @@ bool SMPInstr::IsBenignTruncation(int &IdiomCode) {
 	if (3 == this->GetOptType()) { // Move instruction
 		bool ExtendedLoad = this->MDIsSignedLoad(SignMask);
-		if (ExtendedLoad) {
-			if (SignMask & FG_MASK_UNSIGNED) {
-				// We have a zero-extended load. Compilers zero-extend both
-				//  signed (unfortunately) and unsigned sub-regs when they know
-				//  from the source language types that only the lower bits matter,
-				//  e.g. when a char has been stored in the lower bits and regardless
-				//  of whether that char was sign-extended or zero-extended previously,
-				//  only the char itself is useful info. Otherwise, the compiler could
-				//  move the whole register, e.g. instead of edi := zero-extend(cx), the
-				//  compiler could have generated edi := ecx. The zero-extension loads
-				//  are therefore not good candidates for truncation checks, as they lead
-				//  to lots of false positives.
-				benign = true;
-				IdiomCode = 5;
+		if (ExtendedLoad && (SignMask & FG_MASK_UNSIGNED)) {
+			// We have a zero-extended load. Compilers zero-extend both
+			//  signed (unfortunately) and unsigned sub-regs when they know
+			//  from the source language types that only the lower bits matter,
+			//  e.g. when a char has been stored in the lower bits and regardless
+			//  of whether that char was sign-extended or zero-extended previously,
+			//  only the char itself is useful info. Otherwise, the compiler could
+			//  move the whole register, e.g. instead of edi := zero-extend(cx), the
+			//  compiler could have generated edi := ecx. The zero-extension loads
+			//  are therefore not good candidates for truncation checks, as they lead
+			//  to lots of false positives.
+			benign = true;
+			IdiomCode = 5;
 #if SMP_MEASURE_NUMERIC_ANNOTATIONS
-				++BenignTruncationCount;
+			++BenignTruncationCount;
 #endif
-			}
 		}
 		else { // Move, and not extended load, which was handled above.
 			// Next case: A move instruction whose USE falsely appears to be a truncation,