From a71d00a4d504edfdb09cd169d29ca1bbc0b909c4 Mon Sep 17 00:00:00 2001 From: Andrew Kelley Date: Mon, 27 Jun 2022 19:05:51 -0700 Subject: std.crypto.25519.field: avoid excessive inlining This valid zig code produces reasonable LLVM IR, however, on the wasm32-wasi target, when using the wasmtime runtime, the number of locals of the `isSquare` function exceeds 50000, causing wasmtime to refuse to execute the binary. The `inline` keyword in Zig is intended to be used only where it is semantically necessary; not as an optimization hint. Otherwise, this may produce unwanted binary bloat for the -OReleaseSmall use case. In the future, it is possible that we may end up with both `inline` keyword, which operates as it does in status quo, and additionally `callconv(.inline_hint)` which has no semantic impact, but may be observed by optimization passes. In this commit, I also cleaned up `isSquare` by eliminating an unnecessary mutable variable, replacing it with several local constants. Closes #11947. --- lib/std/crypto/25519/field.zig | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'lib/std/crypto') diff --git a/lib/std/crypto/25519/field.zig b/lib/std/crypto/25519/field.zig index ce021ffb2a..1a786e0c32 100644 --- a/lib/std/crypto/25519/field.zig +++ b/lib/std/crypto/25519/field.zig @@ -341,7 +341,7 @@ pub const Fe = struct { } /// Square a field element `n` times - inline fn sqn(a: Fe, comptime n: comptime_int) Fe { + fn sqn(a: Fe, n: usize) Fe { var i: usize = 0; var fe = a; while (i < n) : (i += 1) { @@ -390,13 +390,12 @@ pub const Fe = struct { const _11 = a.mul(a.sq()); const _1111 = _11.mul(_11.sq().sq()); const _11111111 = _1111.mul(_1111.sq().sq().sq().sq()); - var t = _11111111.sqn(2).mul(_11); - const u = t; - t = t.sqn(10).mul(u).sqn(10).mul(u); - t = t.sqn(30).mul(t); - t = t.sqn(60).mul(t); - t = t.sqn(120).mul(t).sqn(10).mul(u).sqn(3).mul(_11).sq(); - return @bitCast(bool, @truncate(u1, ~(t.toBytes()[1] & 1))); + const u = _11111111.sqn(2).mul(_11); + const t = u.sqn(10).mul(u).sqn(10).mul(u); + const t2 = t.sqn(30).mul(t); + const t3 = t2.sqn(60).mul(t2); + const t4 = t3.sqn(120).mul(t3).sqn(10).mul(u).sqn(3).mul(_11).sq(); + return @bitCast(bool, @truncate(u1, ~(t4.toBytes()[1] & 1))); } fn uncheckedSqrt(x2: Fe) Fe { -- cgit v1.2.3