cranelift: add i64.{ishl,ushr,ashr} libcalls.

These libcalls are useful for 32-bit platforms.

On x86_32 in particular, commit 4ec16fa0 added support for legalizing
64-bit shifts through SIMD operations. However, that legalization
requires SIMD to be enabled and SSE 4.1 to be supported, which is not
acceptable as a hard requirement.

crates/jit/src/link.rs

@@ -50,6 +50,9 @@ fn apply_reloc(
                 SdivI64 => wasmtime_i64_sdiv as usize,
                 UremI64 => wasmtime_i64_urem as usize,
                 SremI64 => wasmtime_i64_srem as usize,
+                IshlI64 => wasmtime_i64_ishl as usize,
+                UshrI64 => wasmtime_i64_ushr as usize,
+                SshrI64 => wasmtime_i64_sshr as usize,
                 CeilF32 => wasmtime_f32_ceil as usize,
                 FloorF32 => wasmtime_f32_floor as usize,
                 TruncF32 => wasmtime_f32_trunc as usize,

crates/runtime/src/libcalls.rs

@@ -98,6 +98,21 @@ pub extern "C" fn wasmtime_i64_srem(x: i64, y: i64) -> i64 {
     x % y
 }
 
+/// Implementation of i64.ishl
+pub extern "C" fn wasmtime_i64_ishl(x: i64, y: i64) -> i64 {
+    x << y
+}
+
+/// Implementation of i64.ushr
+pub extern "C" fn wasmtime_i64_ushr(x: u64, y: i64) -> u64 {
+    x >> y
+}
+
+/// Implementation of i64.sshr
+pub extern "C" fn wasmtime_i64_sshr(x: i64, y: i64) -> i64 {
+    x >> y
+}
+
 /// Implementation of f64.ceil
 pub extern "C" fn wasmtime_f64_ceil(x: f64) -> f64 {
     x.ceil()