Merge bitcoin-core#591: Make bench_internal obey secp256k1_fe_sqrt's contract wrt aliasing.

gmaxwell · gmaxwell · commit 85d0e1bcce8c · 2019-02-24T19:20:54.000Z
b76e45d Make bench_internal obey secp256k1_fe_sqrt's contract wrt aliasing. (Gregory Maxwell) Pull request description: Bench_internal was previously incorrect but wasn't detected by -DVERIFY until PR bitcoin-core#551. Tree-SHA512: 5ecb9e3ba63ddf28cde4012154dbb1dda9b7178016d970dba58a4af20c31aa1ec3458ba2623541233fb16fceff7b3053054d6eee0229d0bfb6281d1a10554e9f
diff --git a/src/bench_internal.c b/src/bench_internal.c
@@ -184,9 +184,11 @@ void bench_field_inverse_var(void* arg) {
 void bench_field_sqrt(void* arg) {
     int i;
     bench_inv *data = (bench_inv*)arg;
+    secp256k1_fe t;
 
     for (i = 0; i < 20000; i++) {
-        secp256k1_fe_sqrt(&data->fe_x, &data->fe_x);
+        t = data->fe_x;
+        secp256k1_fe_sqrt(&data->fe_x, &t);
         secp256k1_fe_add(&data->fe_x, &data->fe_y);
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -184,9 +184,11 @@ void bench_field_inverse_var(void* arg) {`
`184`	`184`	`void bench_field_sqrt(void* arg) {`
`185`	`185`	`int i;`
`186`	`186`	`bench_inv data = (bench_inv)arg;`
	`187`	`+ secp256k1_fe t;`
`187`	`188`
`188`	`189`	`for (i = 0; i < 20000; i++) {`
`189`		`- secp256k1_fe_sqrt(&data->fe_x, &data->fe_x);`
	`190`	`+ t = data->fe_x;`
	`191`	`+ secp256k1_fe_sqrt(&data->fe_x, &t);`
`190`	`192`	`secp256k1_fe_add(&data->fe_x, &data->fe_y);`
`191`	`193`	`}`
`192`	`194`	`}`