Add basic infinite precision tests with random input

Author: tgross35

ci/docker/aarch64-unknown-linux-gnu/Dockerfile

@@ -3,7 +3,7 @@ FROM ubuntu:24.04
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
     gcc libc6-dev ca-certificates \
-    gcc-aarch64-linux-gnu libc6-dev-arm64-cross \
+    gcc-aarch64-linux-gnu m4 make libc6-dev-arm64-cross \
     qemu-user-static
 
 ENV TOOLCHAIN_PREFIX=aarch64-linux-gnu-

ci/docker/i686-unknown-linux-gnu/Dockerfile

@@ -2,4 +2,4 @@ FROM ubuntu:24.04
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-    gcc-multilib libc6-dev ca-certificates
+    gcc-multilib m4 make libc6-dev ca-certificates

ci/docker/x86_64-unknown-linux-gnu/Dockerfile

@@ -2,4 +2,4 @@ FROM ubuntu:24.04
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-    gcc libc6-dev ca-certificates
+    gcc m4 make libc6-dev ca-certificates

ci/run.sh

@@ -24,6 +24,22 @@ case "$target" in
     *thumb*) extra_flags="$extra_flags --exclude musl-math-sys" ;;
 esac
 
+# Configure which targets test against MPFR
+case "$target" in
+    # MSVC cannot link MPFR
+    *windows-msvc*) ;;
+    # FIXME: MinGW should be able to build MPFR, but setup in CI is nontrivial.
+    *windows-gnu*) ;;
+    # Targets that aren't cross compiled work fine
+    # FIXME(ci): we should be able to enable aarch64 Linux here once GHA
+    # support rolls out.
+    x86_64*) extra_flags="$extra_flags --features libm-test/multiprecision-tests" ;;
+    # i686 works fine, i586 does not
+    i686*) extra_flags="$extra_flags --features libm-test/multiprecision-tests" ;;
+    # Apple aarch64 is native
+    aarch64*apple*) extra_flags="$extra_flags --features libm-test/multiprecision-tests" ;;
+esac
+
 # FIXME: `STATUS_DLL_NOT_FOUND` testing macros on CI.
 # <https://github.com/rust-lang/rust/issues/128944>
 case "$target" in

crates/libm-test/Cargo.toml

@@ -10,14 +10,17 @@ default = []
 # Generate tests which are random inputs and the outputs are calculated with
 # musl libc.
 musl-bitwise-tests = ["rand"]
+multiprecision-tests = ["dep:az", "dep:rug"]
 
 [dependencies]
 anyhow = "1.0.90"
+az = { version = "1.2.1", optional = true }
 libm = { path = "../.." }
 libm-macros = { path = "../libm-macros" }
 paste = "1.0.15"
 rand = "0.8.5"
 rand_chacha = "0.3.1"
+rug = { version = "1.26.1", optional = true, default-features = false, features = ["float", "std"] }
 
 [target.'cfg(target_family = "wasm")'.dependencies]
 # Enable randomness on WASM

crates/libm-test/src/lib.rs

@@ -1,4 +1,6 @@
 pub mod gen;
+#[cfg(feature = "multiprecision-tests")]
+pub mod mpfloat;
 mod num_traits;
 mod test_traits;
 
@@ -8,15 +10,19 @@ pub use test_traits::{CheckOutput, GenerateInput, TupleCall};
 // List of all files present in libm's source
 include!(concat!(env!("OUT_DIR"), "/all_files.rs"));
 
-/// ULP allowed to differ from musl (note that musl itself may not be accurate).
+/// Default ULP allowed to differ from musl (note that musl itself may not be accurate).
 const MUSL_DEFAULT_ULP: u32 = 2;
 
-/// Certain functions have different allowed ULP (consider these xfail).
+/// Default ULP allowed to differ from multiprecision (i.e. infinite) results.
+const MULTIPREC_DEFAULT_ULP: u32 = 1;
+
+/// ULP allowed to differ from muls results.
 ///
-/// Currently this includes:
+/// Current overrides includes:
 /// - gamma functions that have higher errors
 /// - 32-bit functions fall back to a less precise algorithm.
 pub fn musl_allowed_ulp(name: &str) -> u32 {
+    // Consider overrides xfail
     match name {
         #[cfg(x86_no_sse)]
         "asinhf" => 6,
@@ -30,3 +36,19 @@ pub fn musl_allowed_ulp(name: &str) -> u32 {
         _ => MUSL_DEFAULT_ULP,
     }
 }
+
+/// ULP allowed to differ from multiprecision results.
+pub fn multiprec_allowed_ulp(name: &str) -> u32 {
+    // Consider overrides xfail
+    match name {
+        "asinh" | "asinhf" => 2,
+        "atanh" | "atanhf" => 2,
+        "exp10" | "exp10f" => 3,
+        "j0" | "j0f" => 2,
+        "lgamma" | "lgammaf" | "lgamma_r" | "lgammaf_r" => 2,
+        "sinh" | "sinhf" => 2,
+        "tanh" | "tanhf" => 2,
+        "tgamma" => 6,
+        _ => MULTIPREC_DEFAULT_ULP,
+    }
+}