Directly use Cranelift instructions for 128bit int shifts

Author: bjorn3

src/codegen_i128.rs

@@ -97,70 +97,23 @@ pub(crate) fn maybe_codegen<'tcx>(
                 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 resolve_value_imm(fx.bcx.func, rhs_val) == Some(64) {
-                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 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_ty = if is_signed {
-                            fx.tcx.types.i128
-                        } else {
-                            fx.tcx.types.u128
-                        };
-                        let val = fx.bcx.ins().iconcat(all_zeros, lhs_lsb);
-                        Some(CValue::by_val(val, fx.layout_of(val_ty)))
-                    }
-                    _ => None,
-                };
-                if let Some(val) = val {
-                    if let Some(is_overflow) = is_overflow {
-                        let out_ty = fx.tcx.mk_tup([lhs.layout().ty, fx.tcx.types.bool].iter());
-                        let val = val.load_scalar(fx);
-                        return Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)));
+            let truncated_rhs = clif_intcast(fx, rhs_val, types::I32, false);
+            let val = match bin_op {
+                BinOp::Shl => fx.bcx.ins().ishl(lhs_val, truncated_rhs),
+                BinOp::Shr => {
+                    if is_signed {
+                        fx.bcx.ins().sshr(lhs_val, truncated_rhs)
                     } else {
-                        return Some(val);
+                        fx.bcx.ins().ushr(lhs_val, truncated_rhs)
                     }
                 }
-            }
-
-            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!(),
+                _ => unreachable!(),
             };
             if let Some(is_overflow) = is_overflow {
                 let out_ty = fx.tcx.mk_tup([lhs.layout().ty, fx.tcx.types.bool].iter());
-                let val = val.load_scalar(fx);
                 Some(CValue::by_val_pair(val, is_overflow, fx.layout_of(out_ty)))
             } else {
-                Some(val)
+                Some(CValue::by_val(val, lhs.layout()))
             }
         }
     }

src/common.rs

@@ -3,8 +3,6 @@ use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::{Integer, Primitive};
 use rustc_target::spec::{HasTargetSpec, Target};
 
-use cranelift_codegen::ir::{InstructionData, Opcode, ValueDef};
-
 use crate::prelude::*;
 
 pub(crate) fn pointer_ty(tcx: TyCtxt<'_>) -> types::Type {
@@ -175,51 +173,6 @@ pub(crate) fn codegen_icmp_imm(
     }
 }
 
-fn resolve_normal_value_imm(func: &Function, val: Value) -> Option<i64> {
-    if let ValueDef::Result(inst, 0 /*param*/) = func.dfg.value_def(val) {
-        if let InstructionData::UnaryImm {
-            opcode: Opcode::Iconst,
-            imm,
-        } = func.dfg[inst]
-        {
-            Some(imm.into())
-        } else {
-            None
-        }
-    } else {
-        None
-    }
-}
-
-fn resolve_128bit_value_imm(func: &Function, val: Value) -> Option<u128> {
-    let (lsb, msb) = if let ValueDef::Result(inst, 0 /*param*/) = func.dfg.value_def(val) {
-        if let InstructionData::Binary {
-            opcode: Opcode::Iconcat,
-            args: [lsb, msb],
-        } = func.dfg[inst]
-        {
-            (lsb, msb)
-        } else {
-            return None;
-        }
-    } else {
-        return None;
-    };
-
-    let lsb = u128::from(resolve_normal_value_imm(func, lsb)? as u64);
-    let msb = u128::from(resolve_normal_value_imm(func, msb)? as u64);
-
-    Some(msb << 64 | lsb)
-}
-
-pub(crate) fn resolve_value_imm(func: &Function, val: Value) -> Option<u128> {
-    if func.dfg.value_type(val) == types::I128 {
-        resolve_128bit_value_imm(func, val)
-    } else {
-        resolve_normal_value_imm(func, val).map(|imm| u128::from(imm as u64))
-    }
-}
-
 pub(crate) fn type_min_max_value(
     bcx: &mut FunctionBuilder<'_>,
     ty: Type,