Both Rust playgrounds (official[1], my take[2]) allow viewing the LLVM IR of a Rust program. The call to the print is call void @_ZN3std2io5stdio6_print

Both Rust playgrounds (official[1], my take[2]) allow viewing the LLVM IR of a Rust program. The call to the print is call void @_ZN3std2io5stdio6_print17h690779b3bd8114d5E(%"core::fmt::Arguments"* noalias nocapture nonnull dereferenceable(48) %_3) The entire chunk of `main` preceding that call: %size = alloca i64, align 8 %_3 = alloca %"core::fmt::Arguments", align 8 %_8 = alloca [1 x %"core::fmt::ArgumentV1"], align 8 %0 = bitcast i64* %size to i8* call void @llvm.lifetime.start(i64 8, i8* %0) store i64 33554432, i64* %size, align 8 %1 = bitcast %"core::fmt::Arguments"* %_3 to i8* call void @llvm.lifetime.start(i64 48, i8* %1) %2 = bitcast [1 x %"core::fmt::ArgumentV1"]* %_8 to i8* call void @llvm.lifetime.start(i64 16, i8* %2) %3 = ptrtoint i64* %size to i64 %4 = bitcast [1 x %"core::fmt::ArgumentV1"]* %_8 to i64* store i64 %3, i64* %4, align 8 %5 = getelementptr inbounds [1 x %"core::fmt::ArgumentV1"], [1 x %"core::fmt::ArgumentV1"]* %_8, i64 0, i64 0, i32 1 %6 = bitcast i8 (%"core::fmt::Void"*, %"core::fmt::Formatter"*)** %5 to i64* store i64 ptrtoint (i8 (i64*, %"core::fmt::Formatter"*)* @"_ZN4core3fmt3num54_$LT$impl$u20$core..fmt..Display$u20$for$u20$usize$GT$3fmt17hb872170870cc06d9E" to i64), i64* %6, align 8 %7 = getelementptr inbounds [1 x %"core::fmt::ArgumentV1"], [1 x %"core::fmt::ArgumentV1"]* %_8, i64 0, i64 0 %8 = getelementptr inbounds %"core::fmt::Arguments", %"core::fmt::Arguments"* %_3, i64 0, i32 0, i32 0 store %str_slice* getelementptr inbounds ([2 x %str_slice], [2 x %str_slice]* @ref.8, i64 0, i64 0), %str_slice** %8, align 8, !alias.scope !1, !noalias !4 %9 = getelementptr inbounds %"core::fmt::Arguments", %"core::fmt::Arguments"* %_3, i64 0, i32 0, i32 1 store i64 2, i64* %9, align 8, !alias.scope !1, !noalias !4 %_6.sroa.0.0..sroa_idx.i = getelementptr inbounds %"core::fmt::Arguments", %"core::fmt::Arguments"* %_3, i64 0, i32 1, i32 0, i32 0 store %"core::fmt::rt::v1::Argument"* null, %"core::fmt::rt::v1::Argument"** %_6.sroa.0.0..sroa_idx.i, align 8, !alias.scope !1, !noalias !4 %10 = getelementptr inbounds %"core::fmt::Arguments", %"core::fmt::Arguments"* %_3, i64 0, i32 2, i32 0 store %"core::fmt::ArgumentV1"* %7, %"core::fmt::ArgumentV1"** %10, align 8, !alias.scope !1, !noalias !4 %11 = getelementptr inbounds %"core::fmt::Arguments", %"core::fmt::Arguments"* %_3, i64 0, i32 2, i32 1 store i64 1, i64* %11, align 8, !alias.scope !1, !noalias !4 call void @_ZN3std2io5stdio6_print17h690779b3bd8114d5E(%"core::fmt::Arguments"* noalias nocapture nonnull dereferenceable(48) %_3) [1]: https://play.rust-lang.org/ https://play.rust-lang.org/ [2]: http://play.integer32.com/ http://play.integer32.com/