Merge pull request #21425 from mlugg/pointer-arith-inplace-res-ty

compiler: provide correct result types to `+=` and `-=`

3 files changed, 45 insertions, 7 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index 559fbe3e53..ded3999b84 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -1361,6 +1361,7 @@ fn analyzeBodyInner(
                     .value_placeholder => unreachable, // never appears in a body
                     .field_parent_ptr => try sema.zirFieldParentPtr(block, extended),
                     .builtin_value => try sema.zirBuiltinValue(extended),
+                    .inplace_arith_result_ty => try sema.zirInplaceArithResultTy(extended),
                 };
             },
 
@@ -27342,6 +27343,33 @@ fn zirBuiltinValue(sema: *Sema, extended: Zir.Inst.Extended.InstData) CompileErr
     return Air.internedToRef(ty.toIntern());
 }
 
+fn zirInplaceArithResultTy(sema: *Sema, extended: Zir.Inst.Extended.InstData) CompileError!Air.Inst.Ref {
+    const pt = sema.pt;
+    const zcu = pt.zcu;
+
+    const lhs = try sema.resolveInst(@enumFromInt(extended.operand));
+    const lhs_ty = sema.typeOf(lhs);
+
+    const op: Zir.Inst.InplaceOp = @enumFromInt(extended.small);
+    const ty: Type = switch (op) {
+        .add_eq => ty: {
+            const ptr_size = lhs_ty.ptrSizeOrNull(zcu) orelse break :ty lhs_ty;
+            switch (ptr_size) {
+                .One, .Slice => break :ty lhs_ty, // invalid, let it error
+                .Many, .C => break :ty .usize, // `[*]T + usize`
+            }
+        },
+        .sub_eq => ty: {
+            const ptr_size = lhs_ty.ptrSizeOrNull(zcu) orelse break :ty lhs_ty;
+            switch (ptr_size) {
+                .One, .Slice => break :ty lhs_ty, // invalid, let it error
+                .Many, .C => break :ty .generic_poison, // could be `[*]T - [*]T` or `[*]T - usize`
+            }
+        },
+    };
+    return Air.internedToRef(ty.toIntern());
+}
+
 fn zirBranchHint(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstData) CompileError!void {
     const pt = sema.pt;
     const zcu = pt.zcu;
diff --git a/src/arch/riscv64/CodeGen.zig b/src/arch/riscv64/CodeGen.zig
index 0c6da840eb..73fa0460de 100644
--- a/src/arch/riscv64/CodeGen.zig
+++ b/src/arch/riscv64/CodeGen.zig
@@ -3897,7 +3897,7 @@ fn airArrayElemVal(func: *Func, inst: Air.Inst.Index) !void {
 
         if (array_ty.isVector(zcu)) {
             // we need to load the vector, vslidedown to get the element we want
-            // and store that element at in a load frame.
+            // and store that element in a load frame.
 
             const src_reg, const src_lock = try func.allocReg(.vector);
             defer func.register_manager.unlockReg(src_lock);
@@ -3970,12 +3970,15 @@ fn airPtrElemVal(func: *Func, inst: Air.Inst.Index) !void {
         };
         defer if (index_lock) |lock| func.register_manager.unlockReg(lock);
 
-        const elem_ptr_reg = if (base_ptr_mcv.isRegister() and func.liveness.operandDies(inst, 0))
-            base_ptr_mcv.register
-        else
-            try func.copyToTmpRegister(base_ptr_ty, base_ptr_mcv);
-        const elem_ptr_lock = func.register_manager.lockRegAssumeUnused(elem_ptr_reg);
-        defer func.register_manager.unlockReg(elem_ptr_lock);
+        const elem_ptr_reg, const elem_ptr_lock = if (base_ptr_mcv.isRegister() and
+            func.liveness.operandDies(inst, 0))
+            .{ base_ptr_mcv.register, null }
+        else blk: {
+            const reg, const lock = try func.allocReg(.int);
+            try func.genSetReg(base_ptr_ty, reg, base_ptr_mcv);
+            break :blk .{ reg, lock };
+        };
+        defer if (elem_ptr_lock) |lock| func.register_manager.unlockReg(lock);
 
         try func.genBinOp(
             .ptr_add,
diff --git a/src/print_zir.zig b/src/print_zir.zig
index f5c83c98e2..c5f1517edd 100644
--- a/src/print_zir.zig
+++ b/src/print_zir.zig
@@ -620,6 +620,7 @@ const Writer = struct {
             .closure_get => try self.writeClosureGet(stream, extended),
             .field_parent_ptr => try self.writeFieldParentPtr(stream, extended),
             .builtin_value => try self.writeBuiltinValue(stream, extended),
+            .inplace_arith_result_ty => try self.writeInplaceArithResultTy(stream, extended),
         }
     }
 
@@ -2781,6 +2782,12 @@ const Writer = struct {
         try self.writeSrcNode(stream, @bitCast(extended.operand));
     }
 
+    fn writeInplaceArithResultTy(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const op: Zir.Inst.InplaceOp = @enumFromInt(extended.small);
+        try self.writeInstRef(stream, @enumFromInt(extended.operand));
+        try stream.print(", {s}))", .{@tagName(op)});
+    }
+
     fn writeInstRef(self: *Writer, stream: anytype, ref: Zir.Inst.Ref) !void {
         if (ref == .none) {
             return stream.writeAll(".none");