commit 7f41e20802fd8f9eb19c0218f1e2000e2751592a (tree)
parent 7c6f5d26eadb137ab3fb2be340485ebd860a85fe
Author: Andrew Kelley <andrew@ziglang.org>
Date: Sat, 15 Jan 2022 23:13:44 -0700
AstGen: emit `as` instructions for branching expressions
There is a mechanism to avoid redundant `as` ZIR instructions which is
to pass `ResultLoc.coerced_ty` instead of `ResultLoc.ty` when it is
known by AstGen that Sema will do the coercion.
This commit downgrades `coerced_ty` to `ty` when a result location
passes through an expression that branches, such as `if`, `switch`,
`while`, and `for`, causing the `as` ZIR instruction to be emitted.
This ensures that the type of a result location will be applied to, e.g.
a `comptime_int` on either side of a branch on a runtime condition.
Diffstat:
3 files changed, 31 insertions(+), 22 deletions(-)
diff --git a/src/AstGen.zig b/src/AstGen.zig
@@ -281,6 +281,15 @@ pub const ResultLoc = union(enum) {
},
}
}
+
+ /// Turns a `coerced_ty` back into a `ty`. Should be called at branch points
+ /// such as if and switch expressions.
+ fn br(rl: ResultLoc) ResultLoc {
+ return switch (rl) {
+ .coerced_ty => |ty| .{ .ty = ty },
+ else => rl,
+ };
+ }
};
pub const align_rl: ResultLoc = .{ .ty = .u16_type };
@@ -748,15 +757,15 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: Ast.Node.Index) InnerEr
.field_access => return fieldAccess(gz, scope, rl, node),
.float_literal => return floatLiteral(gz, rl, node),
- .if_simple => return ifExpr(gz, scope, rl, node, tree.ifSimple(node)),
- .@"if" => return ifExpr(gz, scope, rl, node, tree.ifFull(node)),
+ .if_simple => return ifExpr(gz, scope, rl.br(), node, tree.ifSimple(node)),
+ .@"if" => return ifExpr(gz, scope, rl.br(), node, tree.ifFull(node)),
- .while_simple => return whileExpr(gz, scope, rl, node, tree.whileSimple(node)),
- .while_cont => return whileExpr(gz, scope, rl, node, tree.whileCont(node)),
- .@"while" => return whileExpr(gz, scope, rl, node, tree.whileFull(node)),
+ .while_simple => return whileExpr(gz, scope, rl.br(), node, tree.whileSimple(node)),
+ .while_cont => return whileExpr(gz, scope, rl.br(), node, tree.whileCont(node)),
+ .@"while" => return whileExpr(gz, scope, rl.br(), node, tree.whileFull(node)),
- .for_simple => return forExpr(gz, scope, rl, node, tree.forSimple(node)),
- .@"for" => return forExpr(gz, scope, rl, node, tree.forFull(node)),
+ .for_simple => return forExpr(gz, scope, rl.br(), node, tree.forSimple(node)),
+ .@"for" => return forExpr(gz, scope, rl.br(), node, tree.forFull(node)),
.slice_open => {
const lhs = try expr(gz, scope, .ref, node_datas[node].lhs);
@@ -943,7 +952,7 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: Ast.Node.Index) InnerEr
.error_set_decl => return errorSetDecl(gz, rl, node),
.array_access => return arrayAccess(gz, scope, rl, node),
.@"comptime" => return comptimeExprAst(gz, scope, rl, node),
- .@"switch", .switch_comma => return switchExpr(gz, scope, rl, node),
+ .@"switch", .switch_comma => return switchExpr(gz, scope, rl.br(), node),
.@"nosuspend" => return nosuspendExpr(gz, scope, rl, node),
.@"suspend" => return suspendExpr(gz, scope, node),
diff --git a/test/behavior/array_llvm.zig b/test/behavior/array_llvm.zig
@@ -179,3 +179,17 @@ test "access the null element of a null terminated array" {
try S.doTheTest();
comptime try S.doTheTest();
}
+
+test "type deduction for array subscript expression" {
+ const S = struct {
+ fn doTheTest() !void {
+ var array = [_]u8{ 0x55, 0xAA };
+ var v0 = true;
+ try expect(@as(u8, 0xAA) == array[if (v0) 1 else 0]);
+ var v1 = false;
+ try expect(@as(u8, 0x55) == array[if (v1) 1 else 0]);
+ }
+ };
+ try S.doTheTest();
+ comptime try S.doTheTest();
+}
diff --git a/test/behavior/array_stage1.zig b/test/behavior/array_stage1.zig
@@ -4,20 +4,6 @@ const mem = std.mem;
const expect = testing.expect;
const expectEqual = testing.expectEqual;
-test "type deduction for array subscript expression" {
- const S = struct {
- fn doTheTest() !void {
- var array = [_]u8{ 0x55, 0xAA };
- var v0 = true;
- try expect(@as(u8, 0xAA) == array[if (v0) 1 else 0]);
- var v1 = false;
- try expect(@as(u8, 0x55) == array[if (v1) 1 else 0]);
- }
- };
- try S.doTheTest();
- comptime try S.doTheTest();
-}
-
test "sentinel element count towards the ABI size calculation" {
const S = struct {
fn doTheTest() !void {
