Turn off optimization for MSVC in mutiply and Montgomery_multiply_mod_order. (#110)

cyber-pc · web-flow · commit 14ce54ef03ff · 2025-12-17T13:01:50.000+01:00
diff --git a/k12_and_key_utils.h b/k12_and_key_utils.h
@@ -1277,6 +1277,13 @@ static void table_lookup_fixed_base(point_precomp_t P, unsigned int digit, unsig
     }
 }
 
+// MSVC (VC2022 17.14 specifically) does not strictly preserve left-to-right evaluation order.
+// So turn off the optimization for 2 functions
+// - multiply
+// - Montgomery_multiply_mod_order
+#ifdef _MSC_VER
+#pragma optimize( "", off ) 
+#endif
 static void multiply(const unsigned long long* a, const unsigned long long* b, unsigned long long* c)
 {
     unsigned long long u, v, uv;
@@ -1343,6 +1350,10 @@ static void Montgomery_multiply_mod_order(const unsigned long long* ma, const un
     }
 }
 
+#ifdef _MSC_VER
+#pragma optimize( "", on ) 
+#endif
+
 static void eccnorm(point_extproj_t P, point_t Q)
 { // Normalize a projective point (X1:Y1:Z1), including full reduction
 

Original file line number	Diff line number	Diff line change
`@@ -1277,6 +1277,13 @@ static void table_lookup_fixed_base(point_precomp_t P, unsigned int digit, unsig`
`1277`	`1277`	`}`
`1278`	`1278`	`}`
`1279`	`1279`
	`1280`	`+// MSVC (VC2022 17.14 specifically) does not strictly preserve left-to-right evaluation order.`
	`1281`	`+// So turn off the optimization for 2 functions`
	`1282`	`+// - multiply`
	`1283`	`+// - Montgomery_multiply_mod_order`
	`1284`	`+#ifdef _MSC_VER`
	`1285`	`+#pragma optimize( "", off )`
	`1286`	`+#endif`
`1280`	`1287`	`static void multiply(const unsigned long long* a, const unsigned long long* b, unsigned long long* c)`
`1281`	`1288`	`{`
`1282`	`1289`	`unsigned long long u, v, uv;`
`@@ -1343,6 +1350,10 @@ static void Montgomery_multiply_mod_order(const unsigned long long* ma, const un`
`1343`	`1350`	`}`
`1344`	`1351`	`}`
`1345`	`1352`
	`1353`	`+#ifdef _MSC_VER`
	`1354`	`+#pragma optimize( "", on )`
	`1355`	`+#endif`
	`1356`	`+`
`1346`	`1357`	`static void eccnorm(point_extproj_t P, point_t Q)`
`1347`	`1358`	`{ // Normalize a projective point (X1:Y1:Z1), including full reduction`
`1348`	`1359`