math/big: test that subVW and addVW work with arbitrary y

Fixes #10525.

Change-Id: I92dc87f5d6db396d8dde2220fc37b7093b772d81
Reviewed-on: https://go-review.googlesource.com/9210
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/math/big/arith.go b/src/math/big/arith.go
index 328c85c4f79426be0ee75512d71c371b9375ee29..1ff6349d9d913e068d5cae5b07b12e20aaf5dc53 100644 (file)
--- a/src/math/big/arith.go
+++ b/src/math/big/arith.go
@@ -196,7 +196,6 @@ func subVV_g(z, x, y []Word) (c Word) {
        return
 }
 
-// Argument y must be either 0 or 1.
 // The resulting carry c is either 0 or 1.
 func addVW_g(z, x []Word, y Word) (c Word) {
        if use_addWW_g {

diff --git a/src/math/big/arith_test.go b/src/math/big/arith_test.go
index cd92dd7173aa56de564f033392fb896b9d76e430..f46a494f175b0dcf2eedaf56df65850701b561e4 100644 (file)
--- a/src/math/big/arith_test.go
+++ b/src/math/big/arith_test.go
@@ -155,6 +155,7 @@ var sumVW = []argVW{
        {nat{1}, nat{1}, 0, 0},
        {nat{0}, nat{_M}, 1, 1},
        {nat{0, 0, 0, 0}, nat{_M, _M, _M, _M}, 1, 1},
+       {nat{585}, nat{314}, 271, 0},
 }
 
 var prodVW = []argVW{