From: Chris Duncan <chris@zoso.dev>
Date: Sat, 15 Aug 2026 20:56:36 +0000 (-0700)
Subject: Reduce form on division by shift.
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=0fd8b0f4a6f513bf70b75cccd99ea2c3f01adce1;p=nano25519.git

Reduce form on division by shift.
---

diff --git a/src/assembly/ge.ts b/src/assembly/ge.ts
index 0e68650..c82639f 100644
--- a/src/assembly/ge.ts
+++ b/src/assembly/ge.ts
@@ -140,7 +140,7 @@ export function ge_frombytes (h: ge_p3, s: StaticArray<u8>): i32 {
 	fe_cmov(h.X, x_sqrtm1, 1 - has_m_root)
 
 	fe_neg(negx, h.X)
-	fe_cmov(h.X, negx, fe_isnegative(h.X) ^ ((s[31] >> 5) >> 2))
+	fe_cmov(h.X, negx, fe_isnegative(h.X) ^ (s[31] >> 7))
 	fe_mul(h.T, h.X, h.Y)
 
 	return (has_m_root | has_p_root) - 1
diff --git a/src/assembly/utils.ts b/src/assembly/utils.ts
index e794a08..dee20aa 100644
--- a/src/assembly/utils.ts
+++ b/src/assembly/utils.ts
@@ -7,7 +7,7 @@ export function equal (b: i8, c: i8): u8 {
 	const x: u8 = u8(b) ^ u8(c) /* 0: yes; 1..255: no */
 	let y: u32 = u32(x) /* 0: yes; 1..255: no */
 	y--
-	return u8((y >> 29) >> 2) /* 1: yes; 0: no */
+	return u8(y >> 31) /* 1: yes; 0: no */
 }
 
 //@ts-expect-error
@@ -31,7 +31,7 @@ export function load_4 (input: StaticArray<u8>, i: u8): u64 {
 @inline
 export function negative (b: i8): u8 {
 	const x: u8 = u8(b) /* 0..127: no 128..255: yes */
-	return (x >> 5) >> 2 /* 1: yes; 0: no */
+	return x >> 7 /* 1: yes; 0: no */
 }
 
 //@ts-expect-error