From: Loup Vaillant <loup@loup-vaillant.fr>
Date: Fri, 14 Feb 2020 23:27:25 +0000 (+0100)
Subject: Removed modulo operation in SHA-512
X-Git-Url: https://git.codecow.com/?a=commitdiff_plain;h=d36944946ecda0a48c885702fc4b0b20618ecd16;p=Monocypher.git

Removed modulo operation in SHA-512

While I expect almost all compilers optimise those down to a bit mask in
practice, it can help naive compilers generate better code. The rest of
Monocypher already took this approach, I just forgot about this one.
---

diff --git a/src/optional/monocypher-ed25519.c b/src/optional/monocypher-ed25519.c
index f6b4628..fe844ce 100644
--- a/src/optional/monocypher-ed25519.c
+++ b/src/optional/monocypher-ed25519.c
@@ -163,8 +163,8 @@ static void sha512_set_input(crypto_sha512_ctx *ctx, u8 input)
             ctx->input[i] = 0;
         }
     }
-    size_t word = ctx->input_idx / 8;
-    size_t byte = ctx->input_idx % 8;
+    size_t word = ctx->input_idx >> 3;
+    size_t byte = ctx->input_idx &  7;
     ctx->input[word] |= (u64)input << (8 * (7 - byte));
 }