From 0833a92ddd0bf560afe76accd25c2acaa6617513 Mon Sep 17 00:00:00 2001
From: Chris Fallin <chris@cfallin.org>
Date: Thu, 17 Dec 2020 12:14:53 -0800
Subject: [PATCH] cranelift-native crate: add API variant allowing backend
 selection.

---
 cranelift/native/src/lib.rs | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/cranelift/native/src/lib.rs b/cranelift/native/src/lib.rs
index 668a1934bf..3bd5716dac 100644
--- a/cranelift/native/src/lib.rs
+++ b/cranelift/native/src/lib.rs
@@ -34,10 +34,26 @@ use raw_cpuid::CpuId;
 /// machine, or `Err(())` if the host machine is not supported
 /// in the current configuration.
 pub fn builder() -> Result<isa::Builder, &'static str> {
-    let mut isa_builder = isa::lookup(Triple::host()).map_err(|err| match err {
-        isa::LookupError::SupportDisabled => "support for architecture disabled at compile time",
-        isa::LookupError::Unsupported => "unsupported architecture",
-    })?;
+    builder_with_backend_variant(isa::BackendVariant::Any)
+}
+
+/// Return an `isa` builder configured for the current host
+/// machine, or `Err(())` if the host machine is not supported
+/// in the current configuration.
+///
+/// Selects the given backend variant specifically; this is
+/// useful when more than oen backend exists for a given target
+/// (e.g., on x86-64).
+pub fn builder_with_backend_variant(
+    variant: isa::BackendVariant,
+) -> Result<isa::Builder, &'static str> {
+    let mut isa_builder =
+        isa::lookup_variant(Triple::host(), variant).map_err(|err| match err {
+            isa::LookupError::SupportDisabled => {
+                "support for architecture disabled at compile time"
+            }
+            isa::LookupError::Unsupported => "unsupported architecture",
+        })?;
 
     if cfg!(any(target_arch = "x86", target_arch = "x86_64")) {
         parse_x86_cpuid(&mut isa_builder)?;