Add `uninline-portable` feature

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to Rust's notion of
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- `uninline-portable` feature flag, which disables inlining of some functions.
+  This is useful for tiny microchips (such as ARM Cortex-M0), where inlining
+  can hurt performance and blow up binary size.
 
 ## [0.4.0] - 2022-05-05
 ### Changed

Cargo.toml

@@ -64,3 +64,4 @@ bits = ["ff/bits"]
 gpu = ["alloc", "ec-gpu"]
 sqrt-table = ["alloc", "lazy_static"]
 repr-c = []
+uninline-portable = []

src/fields/fp.rs

@@ -293,7 +293,7 @@ impl Fp {
     }
 
     /// Squares this element.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn square(&self) -> Fp {
         let (r1, carry) = mac(0, self.0[0], self.0[1], 0);
         let (r2, carry) = mac(0, self.0[0], self.0[2], carry);
@@ -373,7 +373,7 @@ impl Fp {
     }
 
     /// Multiplies `rhs` by `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn mul(&self, rhs: &Self) -> Self {
         // Schoolbook multiplication
 
@@ -401,7 +401,7 @@ impl Fp {
     }
 
     /// Subtracts `rhs` from `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn sub(&self, rhs: &Self) -> Self {
         let (d0, borrow) = sbb(self.0[0], rhs.0[0], 0);
         let (d1, borrow) = sbb(self.0[1], rhs.0[1], borrow);
@@ -419,7 +419,7 @@ impl Fp {
     }
 
     /// Adds `rhs` to `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn add(&self, rhs: &Self) -> Self {
         let (d0, carry) = adc(self.0[0], rhs.0[0], 0);
         let (d1, carry) = adc(self.0[1], rhs.0[1], carry);
@@ -432,7 +432,7 @@ impl Fp {
     }
 
     /// Negates `self`.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn neg(&self) -> Self {
         // Subtract `self` from `MODULUS` to negate. Ignore the final
         // borrow because it cannot underflow; self is guaranteed to

src/fields/fq.rs

@@ -293,7 +293,7 @@ impl Fq {
     }
 
     /// Squares this element.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn square(&self) -> Fq {
         let (r1, carry) = mac(0, self.0[0], self.0[1], 0);
         let (r2, carry) = mac(0, self.0[0], self.0[2], carry);
@@ -373,7 +373,7 @@ impl Fq {
     }
 
     /// Multiplies `rhs` by `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn mul(&self, rhs: &Self) -> Self {
         // Schoolbook multiplication
 
@@ -401,7 +401,7 @@ impl Fq {
     }
 
     /// Subtracts `rhs` from `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn sub(&self, rhs: &Self) -> Self {
         let (d0, borrow) = sbb(self.0[0], rhs.0[0], 0);
         let (d1, borrow) = sbb(self.0[1], rhs.0[1], borrow);
@@ -419,7 +419,7 @@ impl Fq {
     }
 
     /// Adds `rhs` to `self`, returning the result.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn add(&self, rhs: &Self) -> Self {
         let (d0, carry) = adc(self.0[0], rhs.0[0], 0);
         let (d1, carry) = adc(self.0[1], rhs.0[1], carry);
@@ -432,7 +432,7 @@ impl Fq {
     }
 
     /// Negates `self`.
-    #[inline]
+    #[cfg_attr(inline, not(feature = "uninline-portable"))]
     pub const fn neg(&self) -> Self {
         // Subtract `self` from `MODULUS` to negate. Ignore the final
         // borrow because it cannot underflow; self is guaranteed to