From: Chris Duncan <chris@zoso.dev>
Date: Fri, 2 Oct 2026 08:36:13 +0000 (-0700)
Subject: Move scratch buffer from fe_isnegative.
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=0002c84177e10cc7fefc1a50ade761380bb36b6f;p=nano25519.git

Move scratch buffer from fe_isnegative.
---

diff --git a/src/assembly/ed25519/fe.ts b/src/assembly/ed25519/fe.ts
index ec1adcd..5d072cd 100644
--- a/src/assembly/ed25519/fe.ts
+++ b/src/assembly/ed25519/fe.ts
@@ -232,7 +232,6 @@ export function fe_invert (out: FieldElement, z: FieldElement): void {
 	fe_mul(out, t1, t0)
 }
 
-const fe_isnegative_t = fe()
 /**
  * return 1 if f is in {1,3,5,...,q-2}
  * return 0 if f is in {0,2,4,...,q-1}
@@ -240,10 +239,9 @@ const fe_isnegative_t = fe()
  * Preconditions:
  * |f| bounded by 1.1x2²⁶,1.1x2²⁵,1.1x2²⁶,1.1x2²⁵,etc.
  */
-export function fe_isnegative (f: FieldElement): u8 {
-	const t = fe_isnegative_t
+export function fe_isnegative (f: FieldElement, t: FieldElement): u8 {
 	fe_reduce(t, f)
-	return load<u8>(changetype<usize>(t), 0) & 1
+	return u8(t[0] & 1)
 }
 
 const fe_iszero_s = new StaticArray<u8>(32)
diff --git a/src/assembly/ed25519/ge.ts b/src/assembly/ed25519/ge.ts
index 93acadb..6bb9928 100644
--- a/src/assembly/ed25519/ge.ts
+++ b/src/assembly/ed25519/ge.ts
@@ -85,6 +85,7 @@ function ge_cmov8_base (t: ge_precomp, bp: usize, b: i8): void {
 	v128.store_lane<u64>(td, v128.bitselect(v128.neg<i32>(d2), d2, n), 0, 32)
 }
 
+const t: FieldElement = fe()
 const u: FieldElement = fe()
 const v: FieldElement = fe()
 const v3: FieldElement = fe()
@@ -140,7 +141,7 @@ export function ge_frombytes_negate_vartime (h: ge_p3, s: StaticArray<u8>): i32
 		fe_mul(h.X, h.X, fe_sqrtm1)
 	}
 
-	if (fe_isnegative(h.X) == (s[31] >> 7)) {
+	if (fe_isnegative(h.X, t) == (s[31] >> 7)) {
 		fe_neg(h.X, h.X)
 	}
 	fe_mul(h.T, h.X, h.Y)
@@ -148,6 +149,7 @@ export function ge_frombytes_negate_vartime (h: ge_p3, s: StaticArray<u8>): i32
 	return 0
 }
 
+const ge_frombytes_t: FieldElement = fe()
 const ge_frombytes_u: FieldElement = fe()
 const ge_frombytes_v: FieldElement = fe()
 const ge_frombytes_vxx: FieldElement = fe()
@@ -161,6 +163,7 @@ const x_sqrtm1: FieldElement = fe()
  * @returns {i32} 0 if `s` decodes to a valid point, else -1
  */
 export function ge_frombytes (h: ge_p3, s: StaticArray<u8>): i32 {
+	const t = ge_frombytes_t
 	const u = ge_frombytes_u
 	const v = ge_frombytes_v
 	const vxx = ge_frombytes_vxx
@@ -202,7 +205,7 @@ 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] >> 7))
+	fe_cmov(h.X, negx, fe_isnegative(h.X, t) ^ (s[31] >> 7))
 	fe_mul(h.T, h.X, h.Y)
 
 	return i32(has_m_root | has_p_root) - 1
diff --git a/src/assembly/ed25519/p.ts b/src/assembly/ed25519/p.ts
index 4ee65f4..401cd0f 100644
--- a/src/assembly/ed25519/p.ts
+++ b/src/assembly/ed25519/p.ts
@@ -118,7 +118,7 @@ export function ge_p3_tobytes (s: StaticArray<u8>, h: ge_p3): void {
 	fe_mul(x, h.X, recip)
 	fe_mul(y, h.Y, recip)
 	fe_tobytes(s, y, t)
-	s[31] ^= fe_isnegative(x) << 7
+	s[31] ^= fe_isnegative(x, t) << 7
 }
 
 const ge_p2_dbl_t: FieldElement = fe()