Implement 128bit shl and shr binops

src/codegen_i128.rs

@@ -19,7 +19,13 @@ pub fn maybe_codegen<'a, 'tcx>(
     let rhs_val = rhs.load_scalar(fx);
 
     match bin_op {
-        BinOp::Add | BinOp::Sub | BinOp::BitAnd | BinOp::BitOr | BinOp::BitXor => return None,
+        BinOp::BitAnd | BinOp::BitOr | BinOp::BitXor => {
+            assert!(!checked);
+            return None;
+        }
+        BinOp::Add | BinOp::Sub => {
+            return None; // FIXME implement checked versions
+        }
         BinOp::Offset => unreachable!("offset should only be used on pointers, not 128bit ints"),
         BinOp::Mul => {
             let res = if checked {
@@ -99,9 +105,79 @@ pub fn maybe_codegen<'a, 'tcx>(
             return Some(res);
         }
         BinOp::Shl | BinOp::Shr => {
-            // FIXME implement it
-            let out_layout = fx.layout_of(out_ty);
-            return Some(crate::trap::trap_unreachable_ret_value(fx, out_layout, format!("unimplemented 128bit binop {:?}", bin_op)));
+            let is_overflow = if checked {
+                // rhs >= 128
+
+                // FIXME support non 128bit rhs
+                /*let (rhs_lsb, rhs_msb) = fx.bcx.ins().isplit(rhs_val);
+                let rhs_msb_gt_0 = fx.bcx.ins().icmp_imm(IntCC::NotEqual, rhs_msb, 0);
+                let rhs_lsb_ge_128 = fx.bcx.ins().icmp_imm(IntCC::SignedGreaterThan, rhs_lsb, 127);
+                let is_overflow = fx.bcx.ins().bor(rhs_msb_gt_0, rhs_lsb_ge_128);*/
+                let is_overflow = fx.bcx.ins().bconst(types::B1, false);
+
+                Some(fx.bcx.ins().bint(types::I8, is_overflow))
+            } else {
+                None
+            };
+
+            // Optimize `val >> 64`, because compiler_builtins uses it to deconstruct an 128bit
+            // integer into its lsb and msb.
+            // https://github.com/rust-lang-nursery/compiler-builtins/blob/79a6a1603d5672cbb9187ff41ff4d9b5048ac1cb/src/int/mod.rs#L217
+            if let Some(64) = resolve_value_imm(fx.bcx.func, rhs_val) {
+                let (lhs_lsb, lhs_msb) = fx.bcx.ins().isplit(lhs_val);
+                let all_zeros = fx.bcx.ins().iconst(types::I64, 0);
+                let val = match (bin_op, is_signed) {
+                    (BinOp::Shr, false) => {
+                        let val = fx.bcx.ins().iconcat(lhs_msb, all_zeros);
+                        Some(CValue::by_val(val, fx.layout_of(fx.tcx.types.u128)))
+                    }
+                    (BinOp::Shr, true) => {
+                        let sign = fx.bcx.ins().icmp_imm(IntCC::SignedLessThan, lhs_msb, 0);
+                        let all_ones = fx.bcx.ins().iconst(types::I64, u64::max_value() as i64);
+                        let all_sign_bits = fx.bcx.ins().select(sign, all_zeros, all_ones);
+
+                        let val = fx.bcx.ins().iconcat(lhs_msb, all_sign_bits);
+                        Some(CValue::by_val(val, fx.layout_of(fx.tcx.types.i128)))
+                    }
+                    (BinOp::Shl, _) => {
+                        let val = fx.bcx.ins().iconcat(all_zeros, lhs_lsb);
+                        Some(CValue::by_val(val, fx.layout_of(out_ty)))
+                    }
+                    _ => None
+                };
+                if let Some(val) = val {
+                    if let Some(is_overflow) = is_overflow {
+                        let val = val.load_scalar(fx);
+                        return Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)))
+                    } else {
+                        return Some(val);
+                    }
+                }
+            }
+
+            let truncated_rhs = clif_intcast(fx, rhs_val, types::I32, false);
+            let truncated_rhs = CValue::by_val(truncated_rhs, fx.layout_of(fx.tcx.types.u32));
+            let val = match (bin_op, is_signed) {
+                (BinOp::Shl, false) => {
+                    fx.easy_call("__ashlti3", &[lhs, truncated_rhs], fx.tcx.types.u128)
+                }
+                (BinOp::Shl, true) => {
+                    fx.easy_call("__ashlti3", &[lhs, truncated_rhs], fx.tcx.types.i128)
+                }
+                (BinOp::Shr, false) => {
+                    fx.easy_call("__lshrti3", &[lhs, truncated_rhs], fx.tcx.types.u128)
+                }
+                (BinOp::Shr, true) => {
+                    fx.easy_call("__ashrti3", &[lhs, truncated_rhs], fx.tcx.types.i128)
+                }
+                (_, _) => unreachable!(),
+            };
+            if let Some(is_overflow) = is_overflow {
+                let val = val.load_scalar(fx);
+                Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)))
+            } else {
+                Some(val)
+            }
         }
     }
 }