From: Chris Duncan <chris@zoso.dev>
Date: Fri, 2 Oct 2026 05:33:50 +0000 (-0700)
Subject: Eliminate another scratch buffer.
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=3e5718ac32c0ef459a989f9182f9e0c434009125;p=nano25519.git

Eliminate another scratch buffer.
---

diff --git a/src/assembly/ed25519/p.ts b/src/assembly/ed25519/p.ts
index f43c362..6be8019 100644
--- a/src/assembly/ed25519/p.ts
+++ b/src/assembly/ed25519/p.ts
@@ -190,24 +190,25 @@ export function ge_add_cached (r: ge_p1p1, p: ge_p3, q: ge_cached): void {
 	fe_sub(r.T, t0, r.T)
 }
 
-const ge_add_precomp_t0: FieldElement = fe()
 /**
- * r = p + q
+ * `r = p + q`
+ *
+ * `p.Z` is doubled and stored to itself because its value is not referenced
+ * again before being reassigned at all three call sites of this function.
  */
 //@ts-expect-error
 @inline
 export function ge_add_precomp (r: ge_p1p1, p: ge_p3, q: ge_precomp): void {
-	const t0 = ge_add_precomp_t0
 	fe_add(r.X, p.Y, p.X)
 	fe_sub(r.Y, p.Y, p.X)
 	fe_mul(r.Z, r.X, q.yplusx)
 	fe_mul(r.Y, r.Y, q.yminusx)
 	fe_mul(r.T, q.xy2d, p.T)
-	fe_dbl(t0, p.Z)
+	fe_dbl(p.Z, p.Z)
 	fe_sub(r.X, r.Z, r.Y)
 	fe_add(r.Y, r.Z, r.Y)
-	fe_add(r.Z, t0, r.T)
-	fe_sub(r.T, t0, r.T)
+	fe_add(r.Z, p.Z, r.T)
+	fe_sub(r.T, p.Z, r.T)
 }
 
 const ge_sub_p3_q_cached = new ge_cached()