Merge pull request #12164 from ziglang/llvm-opt-byref

LLVM: lower optional types as byref=true

1 files changed, 162 insertions, 66 deletions

diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index d34bdea766..53c97c880f 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -4539,7 +4539,7 @@ pub const FuncGen = struct {
                 }
                 // We need to emit instructions to check for equality/inequality
                 // of optionals that are not pointers.
-                const is_by_ref = isByRef(operand_ty);
+                const is_by_ref = isByRef(scalar_ty);
                 const lhs_non_null = self.optIsNonNull(lhs, is_by_ref);
                 const rhs_non_null = self.optIsNonNull(rhs, is_by_ref);
                 const llvm_i2 = self.context.intType(2);
@@ -4564,8 +4564,8 @@ pub const FuncGen = struct {
                 _ = self.builder.buildBr(end_block);
 
                 self.builder.positionBuilderAtEnd(both_pl_block);
-                const lhs_payload = self.optPayloadHandle(lhs, is_by_ref);
-                const rhs_payload = self.optPayloadHandle(rhs, is_by_ref);
+                const lhs_payload = self.optPayloadHandle(lhs, scalar_ty);
+                const rhs_payload = self.optPayloadHandle(rhs, scalar_ty);
                 const payload_cmp = try self.cmp(lhs_payload, rhs_payload, payload_ty, op);
                 _ = self.builder.buildBr(end_block);
                 const both_pl_block_end = self.builder.getInsertBlock();
@@ -4740,12 +4740,14 @@ pub const FuncGen = struct {
                 const err_set_ty = try fg.dg.lowerType(Type.anyerror);
                 const zero = err_set_ty.constNull();
                 if (!payload_has_bits) {
+                    // TODO add alignment to this load
                     const loaded = if (operand_is_ptr) fg.builder.buildLoad(err_union, "") else err_union;
                     break :err fg.builder.buildICmp(.NE, loaded, zero, "");
                 }
                 const err_field_index = errUnionErrorOffset(payload_ty, target);
                 if (operand_is_ptr or isByRef(err_union_ty)) {
                     const err_field_ptr = fg.builder.buildStructGEP(err_union, err_field_index, "");
+                    // TODO add alignment to this load
                     const loaded = fg.builder.buildLoad(err_field_ptr, "");
                     break :err fg.builder.buildICmp(.NE, loaded, zero, "");
                 }
@@ -4765,13 +4767,22 @@ pub const FuncGen = struct {
         if (!payload_has_bits) {
             if (!operand_is_ptr) return null;
 
-            // TODO once we update to LLVM 14 this bitcast won't be necessary.
+            // TODO once we update to an LLVM version with opaque pointers
+            // this bitcast won't be necessary.
             const res_ptr_ty = try fg.dg.lowerType(result_ty);
             return fg.builder.buildBitCast(err_union, res_ptr_ty, "");
         }
         const offset = errUnionPayloadOffset(payload_ty, target);
         if (operand_is_ptr or isByRef(payload_ty)) {
             return fg.builder.buildStructGEP(err_union, offset, "");
+        } else if (isByRef(err_union_ty)) {
+            const payload_ptr = fg.builder.buildStructGEP(err_union, offset, "");
+            if (isByRef(payload_ty)) {
+                return payload_ptr;
+            }
+            const load_inst = fg.builder.buildLoad(payload_ptr, "");
+            load_inst.setAlignment(payload_ty.abiAlignment(target));
+            return load_inst;
         }
         return fg.builder.buildExtractValue(err_union, offset, "");
     }
@@ -5730,12 +5741,7 @@ pub const FuncGen = struct {
             // The payload and the optional are the same value.
             return operand;
         }
-        const index_type = self.context.intType(32);
-        const indices: [2]*const llvm.Value = .{
-            index_type.constNull(), // dereference the pointer
-            index_type.constNull(), // first field is the payload
-        };
-        return self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
+        return self.builder.buildStructGEP(operand, 0, "");
     }
 
     fn airOptionalPayloadPtrSet(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
@@ -5761,24 +5767,17 @@ pub const FuncGen = struct {
             // Setting to non-null will be done when the payload is set.
             return operand;
         }
-        const index_type = self.context.intType(32);
-        {
-            // First set the non-null bit.
-            const indices: [2]*const llvm.Value = .{
-                index_type.constNull(), // dereference the pointer
-                index_type.constInt(1, .False), // second field is the non-null bit
-            };
-            const non_null_ptr = self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
-            _ = self.builder.buildStore(non_null_bit, non_null_ptr);
-        }
+
+        // First set the non-null bit.
+        const non_null_ptr = self.builder.buildStructGEP(operand, 1, "");
+        // TODO set alignment on this store
+        _ = self.builder.buildStore(non_null_bit, non_null_ptr);
+
         // Then return the payload pointer (only if it's used).
         if (self.liveness.isUnused(inst))
             return null;
-        const indices: [2]*const llvm.Value = .{
-            index_type.constNull(), // dereference the pointer
-            index_type.constNull(), // first field is the payload
-        };
-        return self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
+
+        return self.builder.buildStructGEP(operand, 0, "");
     }
 
     fn airOptionalPayload(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
@@ -5795,7 +5794,7 @@ pub const FuncGen = struct {
             return operand;
         }
 
-        return self.optPayloadHandle(operand, isByRef(payload_ty));
+        return self.optPayloadHandle(operand, optional_ty);
     }
 
     fn airErrUnionPayload(
@@ -5807,6 +5806,8 @@ pub const FuncGen = struct {
 
         const ty_op = self.air.instructions.items(.data)[inst].ty_op;
         const operand = try self.resolveInst(ty_op.operand);
+        const operand_ty = self.air.typeOf(ty_op.operand);
+        const err_union_ty = if (operand_is_ptr) operand_ty.childType() else operand_ty;
         const result_ty = self.air.typeOfIndex(inst);
         const payload_ty = if (operand_is_ptr) result_ty.childType() else result_ty;
         const target = self.dg.module.getTarget();
@@ -5821,6 +5822,14 @@ pub const FuncGen = struct {
         const offset = errUnionPayloadOffset(payload_ty, target);
         if (operand_is_ptr or isByRef(payload_ty)) {
             return self.builder.buildStructGEP(operand, offset, "");
+        } else if (isByRef(err_union_ty)) {
+            const payload_ptr = self.builder.buildStructGEP(operand, offset, "");
+            if (isByRef(payload_ty)) {
+                return payload_ptr;
+            }
+            const load_inst = self.builder.buildLoad(payload_ptr, "");
+            load_inst.setAlignment(payload_ty.abiAlignment(target));
+            return load_inst;
         }
         return self.builder.buildExtractValue(operand, offset, "");
     }
@@ -5874,16 +5883,11 @@ pub const FuncGen = struct {
             _ = self.builder.buildStore(non_error_val, operand);
             return operand;
         }
-        const index_type = self.context.intType(32);
         const target = self.dg.module.getTarget();
         {
             const error_offset = errUnionErrorOffset(payload_ty, target);
             // First set the non-error value.
-            const indices: [2]*const llvm.Value = .{
-                index_type.constNull(), // dereference the pointer
-                index_type.constInt(error_offset, .False),
-            };
-            const non_null_ptr = self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
+            const non_null_ptr = self.builder.buildStructGEP(operand, error_offset, "");
             const store_inst = self.builder.buildStore(non_error_val, non_null_ptr);
             store_inst.setAlignment(Type.anyerror.abiAlignment(target));
         }
@@ -5892,11 +5896,7 @@ pub const FuncGen = struct {
             return null;
 
         const payload_offset = errUnionPayloadOffset(payload_ty, target);
-        const indices: [2]*const llvm.Value = .{
-            index_type.constNull(), // dereference the pointer
-            index_type.constInt(payload_offset, .False),
-        };
-        return self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
+        return self.builder.buildStructGEP(operand, payload_offset, "");
     }
 
     fn airErrReturnTrace(self: *FuncGen, _: Air.Inst.Index) !?*const llvm.Value {
@@ -6391,8 +6391,30 @@ pub const FuncGen = struct {
         const overflow_bit = self.builder.buildExtractValue(result_struct, 1, "");
 
         var ty_buf: Type.Payload.Pointer = undefined;
-        const partial = self.builder.buildInsertValue(llvm_dest_ty.getUndef(), result, llvmFieldIndex(dest_ty, 0, tg, &ty_buf).?, "");
-        return self.builder.buildInsertValue(partial, overflow_bit, llvmFieldIndex(dest_ty, 1, tg, &ty_buf).?, "");
+        const result_index = llvmFieldIndex(dest_ty, 0, tg, &ty_buf).?;
+        const overflow_index = llvmFieldIndex(dest_ty, 1, tg, &ty_buf).?;
+
+        if (isByRef(dest_ty)) {
+            const target = self.dg.module.getTarget();
+            const alloca_inst = self.buildAlloca(llvm_dest_ty);
+            const result_alignment = dest_ty.abiAlignment(target);
+            alloca_inst.setAlignment(result_alignment);
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, result_index, "");
+                const store_inst = self.builder.buildStore(result, field_ptr);
+                store_inst.setAlignment(result_alignment);
+            }
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, overflow_index, "");
+                const store_inst = self.builder.buildStore(overflow_bit, field_ptr);
+                store_inst.setAlignment(1);
+            }
+
+            return alloca_inst;
+        }
+
+        const partial = self.builder.buildInsertValue(llvm_dest_ty.getUndef(), result, result_index, "");
+        return self.builder.buildInsertValue(partial, overflow_bit, overflow_index, "");
     }
 
     fn buildElementwiseCall(
@@ -6721,8 +6743,30 @@ pub const FuncGen = struct {
         const overflow_bit = self.builder.buildICmp(.NE, lhs, reconstructed, "");
 
         var ty_buf: Type.Payload.Pointer = undefined;
-        const partial = self.builder.buildInsertValue(llvm_dest_ty.getUndef(), result, llvmFieldIndex(dest_ty, 0, tg, &ty_buf).?, "");
-        return self.builder.buildInsertValue(partial, overflow_bit, llvmFieldIndex(dest_ty, 1, tg, &ty_buf).?, "");
+        const result_index = llvmFieldIndex(dest_ty, 0, tg, &ty_buf).?;
+        const overflow_index = llvmFieldIndex(dest_ty, 1, tg, &ty_buf).?;
+
+        if (isByRef(dest_ty)) {
+            const target = self.dg.module.getTarget();
+            const alloca_inst = self.buildAlloca(llvm_dest_ty);
+            const result_alignment = dest_ty.abiAlignment(target);
+            alloca_inst.setAlignment(result_alignment);
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, result_index, "");
+                const store_inst = self.builder.buildStore(result, field_ptr);
+                store_inst.setAlignment(result_alignment);
+            }
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, overflow_index, "");
+                const store_inst = self.builder.buildStore(overflow_bit, field_ptr);
+                store_inst.setAlignment(1);
+            }
+
+            return alloca_inst;
+        }
+
+        const partial = self.builder.buildInsertValue(llvm_dest_ty.getUndef(), result, result_index, "");
+        return self.builder.buildInsertValue(partial, overflow_bit, overflow_index, "");
     }
 
     fn airAnd(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
@@ -7347,11 +7391,9 @@ pub const FuncGen = struct {
         }
 
         comptime assert(optional_layout_version == 3);
-        const optional_llvm_ty = try self.dg.lowerType(optional_ty);
+
         const non_null_bit = self.builder.buildNot(success_bit, "");
-        const non_null_field = self.builder.buildZExt(non_null_bit, self.dg.context.intType(8), "");
-        const partial = self.builder.buildInsertValue(optional_llvm_ty.getUndef(), payload, 0, "");
-        return self.builder.buildInsertValue(partial, non_null_field, 1, "");
+        return buildOptional(self, optional_ty, payload, non_null_bit);
     }
 
     fn airAtomicRmw(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
@@ -7515,11 +7557,13 @@ pub const FuncGen = struct {
         const union_ptr = try self.resolveInst(bin_op.lhs);
         const new_tag = try self.resolveInst(bin_op.rhs);
         if (layout.payload_size == 0) {
+            // TODO alignment on this store
             _ = self.builder.buildStore(new_tag, union_ptr);
             return null;
         }
         const tag_index = @boolToInt(layout.tag_align < layout.payload_align);
         const tag_field_ptr = self.builder.buildStructGEP(union_ptr, tag_index, "");
+        // TODO alignment on this store
         _ = self.builder.buildStore(new_tag, tag_field_ptr);
         return null;
     }
@@ -8336,17 +8380,9 @@ pub const FuncGen = struct {
     fn optIsNonNull(self: *FuncGen, opt_handle: *const llvm.Value, is_by_ref: bool) *const llvm.Value {
         const field = b: {
             if (is_by_ref) {
-                const index_type = self.context.intType(32);
-
-                const indices: [2]*const llvm.Value = .{
-                    index_type.constNull(),
-                    index_type.constInt(1, .False),
-                };
-
-                const field_ptr = self.builder.buildInBoundsGEP(opt_handle, &indices, indices.len, "");
+                const field_ptr = self.builder.buildStructGEP(opt_handle, 1, "");
                 break :b self.builder.buildLoad(field_ptr, "");
             }
-
             break :b self.builder.buildExtractValue(opt_handle, 1, "");
         };
         comptime assert(optional_layout_version == 3);
@@ -8355,18 +8391,63 @@ pub const FuncGen = struct {
     }
 
     /// Assumes the optional is not pointer-like and payload has bits.
-    fn optPayloadHandle(self: *FuncGen, opt_handle: *const llvm.Value, is_by_ref: bool) *const llvm.Value {
-        if (is_by_ref) {
+    fn optPayloadHandle(
+        fg: *FuncGen,
+        opt_handle: *const llvm.Value,
+        opt_ty: Type,
+    ) *const llvm.Value {
+        var buf: Type.Payload.ElemType = undefined;
+        const payload_ty = opt_ty.optionalChild(&buf);
+
+        if (isByRef(opt_ty)) {
             // We have a pointer and we need to return a pointer to the first field.
-            const index_type = self.context.intType(32);
-            const indices: [2]*const llvm.Value = .{
-                index_type.constNull(), // dereference the pointer
-                index_type.constNull(), // first field is the payload
-            };
-            return self.builder.buildInBoundsGEP(opt_handle, &indices, indices.len, "");
+            const payload_ptr = fg.builder.buildStructGEP(opt_handle, 0, "");
+
+            if (isByRef(payload_ty)) {
+                return payload_ptr;
+            }
+            const target = fg.dg.module.getTarget();
+            const payload_alignment = payload_ty.abiAlignment(target);
+            const load_inst = fg.builder.buildLoad(payload_ptr, "");
+            load_inst.setAlignment(payload_alignment);
+            return load_inst;
+        }
+
+        assert(!isByRef(payload_ty));
+        return fg.builder.buildExtractValue(opt_handle, 0, "");
+    }
+
+    fn buildOptional(
+        self: *FuncGen,
+        optional_ty: Type,
+        payload: *const llvm.Value,
+        non_null_bit: *const llvm.Value,
+    ) !?*const llvm.Value {
+        const optional_llvm_ty = try self.dg.lowerType(optional_ty);
+        const non_null_field = self.builder.buildZExt(non_null_bit, self.dg.context.intType(8), "");
+
+        if (isByRef(optional_ty)) {
+            const target = self.dg.module.getTarget();
+            const alloca_inst = self.buildAlloca(optional_llvm_ty);
+            const payload_alignment = optional_ty.abiAlignment(target);
+            alloca_inst.setAlignment(payload_alignment);
+
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, 0, "");
+                const store_inst = self.builder.buildStore(payload, field_ptr);
+                store_inst.setAlignment(payload_alignment);
+            }
+            {
+                const field_ptr = self.builder.buildStructGEP(alloca_inst, 1, "");
+                const store_inst = self.builder.buildStore(non_null_field, field_ptr);
+                store_inst.setAlignment(1);
+            }
+
+            return alloca_inst;
         }
 
-        return self.builder.buildExtractValue(opt_handle, 0, "");
+        const partial = self.builder.buildInsertValue(optional_llvm_ty.getUndef(), payload, 0, "");
+        return self.builder.buildInsertValue(partial, non_null_field, 1, "");
     }
 
     fn fieldPtr(
@@ -9275,10 +9356,12 @@ fn ccAbiPromoteInt(
     return null;
 }
 
+/// This is the one source of truth for whether a type is passed around as an LLVM pointer,
+/// or as an LLVM value.
 fn isByRef(ty: Type) bool {
     // For tuples and structs, if there are more than this many non-void
     // fields, then we make it byref, otherwise byval.
-    const max_fields_byval = 2;
+    const max_fields_byval = 0;
 
     switch (ty.zigTypeTag()) {
         .Type,
@@ -9332,10 +9415,23 @@ fn isByRef(ty: Type) bool {
             return false;
         },
         .Union => return ty.hasRuntimeBits(),
-        .ErrorUnion => return isByRef(ty.errorUnionPayload()),
+        .ErrorUnion => {
+            const payload_ty = ty.errorUnionPayload();
+            if (!payload_ty.hasRuntimeBitsIgnoreComptime()) {
+                return false;
+            }
+            return true;
+        },
         .Optional => {
             var buf: Type.Payload.ElemType = undefined;
-            return isByRef(ty.optionalChild(&buf));
+            const payload_ty = ty.optionalChild(&buf);
+            if (!payload_ty.hasRuntimeBitsIgnoreComptime()) {
+                return false;
+            }
+            if (ty.optionalReprIsPayload()) {
+                return false;
+            }
+            return true;
         },
     }
 }