From c818f89db699145c1757f65d0081554022ef9b83 Mon Sep 17 00:00:00 2001
From: Jack Lloyd <jack.lloyd@dfinity.org>
Date: Wed, 18 Oct 2023 15:03:00 -0400
Subject: [PATCH] Add inline annotations on conditional_select in p256, k256,
 and primeorder

This seems to help situations where the Rust compiler otherwise will not
completely inline conditional_select, causing algoritms which depend on this to
become significantly slower than they would otherwise.

See #940 for discussion.
---
 k256/src/arithmetic/field.rs             | 1 +
 k256/src/arithmetic/field/field_10x26.rs | 1 +
 k256/src/arithmetic/field/field_5x52.rs  | 1 +
 k256/src/arithmetic/field/field_impl.rs  | 1 +
 p256/src/arithmetic/field.rs             | 1 +
 primeorder/src/affine.rs                 | 1 +
 primeorder/src/projective.rs             | 1 +
 7 files changed, 7 insertions(+)

diff --git a/k256/src/arithmetic/field.rs b/k256/src/arithmetic/field.rs
index 6e97ee78..7e68f1b4 100644
--- a/k256/src/arithmetic/field.rs
+++ b/k256/src/arithmetic/field.rs
@@ -323,6 +323,7 @@ impl PrimeField for FieldElement {
 }
 
 impl ConditionallySelectable for FieldElement {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         Self(FieldElementImpl::conditional_select(&(a.0), &(b.0), choice))
     }
diff --git a/k256/src/arithmetic/field/field_10x26.rs b/k256/src/arithmetic/field/field_10x26.rs
index d3c5706d..6ea525a0 100644
--- a/k256/src/arithmetic/field/field_10x26.rs
+++ b/k256/src/arithmetic/field/field_10x26.rs
@@ -674,6 +674,7 @@ impl Default for FieldElement10x26 {
 }
 
 impl ConditionallySelectable for FieldElement10x26 {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         Self([
             u32::conditional_select(&a.0[0], &b.0[0], choice),
diff --git a/k256/src/arithmetic/field/field_5x52.rs b/k256/src/arithmetic/field/field_5x52.rs
index 06735ade..3653ec50 100644
--- a/k256/src/arithmetic/field/field_5x52.rs
+++ b/k256/src/arithmetic/field/field_5x52.rs
@@ -461,6 +461,7 @@ impl Default for FieldElement5x52 {
 }
 
 impl ConditionallySelectable for FieldElement5x52 {
+    #[inline(always)]
     fn conditional_select(
         a: &FieldElement5x52,
         b: &FieldElement5x52,
diff --git a/k256/src/arithmetic/field/field_impl.rs b/k256/src/arithmetic/field/field_impl.rs
index 4fa1f4f5..6c7820b1 100644
--- a/k256/src/arithmetic/field/field_impl.rs
+++ b/k256/src/arithmetic/field/field_impl.rs
@@ -142,6 +142,7 @@ impl Default for FieldElementImpl {
 }
 
 impl ConditionallySelectable for FieldElementImpl {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         // 1. It's debug only, so it shouldn't present a security risk
         // 2. Being normalized does is independent from the field element value;
diff --git a/p256/src/arithmetic/field.rs b/p256/src/arithmetic/field.rs
index ea153a88..86462f6a 100644
--- a/p256/src/arithmetic/field.rs
+++ b/p256/src/arithmetic/field.rs
@@ -473,6 +473,7 @@ impl PrimeField for FieldElement {
 }
 
 impl ConditionallySelectable for FieldElement {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         Self(U256::conditional_select(&a.0, &b.0, choice))
     }
diff --git a/primeorder/src/affine.rs b/primeorder/src/affine.rs
index 3fb01d90..6801c5d3 100644
--- a/primeorder/src/affine.rs
+++ b/primeorder/src/affine.rs
@@ -96,6 +96,7 @@ impl<C> ConditionallySelectable for AffinePoint<C>
 where
     C: PrimeCurveParams,
 {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         Self {
             x: C::FieldElement::conditional_select(&a.x, &b.x, choice),
diff --git a/primeorder/src/projective.rs b/primeorder/src/projective.rs
index 5549543f..dc30f532 100644
--- a/primeorder/src/projective.rs
+++ b/primeorder/src/projective.rs
@@ -172,6 +172,7 @@ impl<C> ConditionallySelectable for ProjectivePoint<C>
 where
     C: PrimeCurveParams,
 {
+    #[inline(always)]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
         Self {
             x: C::FieldElement::conditional_select(&a.x, &b.x, choice),