motiejus/zig
1
Fork 0
Code Releases Activity

AstGen: coerce break operands of labeled blocks

Browse Source 
Similar code was already in place for conditional branches. This updates
AstGen to do the same for labeled blocks. It takes advantage of the
`store_to_block_ptr` instructions by mutating them in place to become
`as` instructions, coercing the break operands before they are returned
from the block.
This commit is contained in:
Andrew Kelley
2022-03-28 18:28:08 -07:00
parent 857743473c
commit 4dd65316b7
2 changed files with 39 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
src/AstGen.zig
View File

@@ -2015,6 +2015,7 @@ fn labeledBlockExpr(
}
const zir_datas = gz.astgen.instructions.items(.data);
const zir_tags = gz.astgen.instructions.items(.tag);
const strat = rl.strategy(&block_scope);
switch (strat.tag) {
.break_void => {
@@ -2029,6 +2030,31 @@ fn labeledBlockExpr(
},
.break_operand => {
// All break operands are values that did not use the result location pointer.
// The break instructions need to have their operands coerced if the
// block's result location is a `ty`. In this case we overwrite the
// `store_to_block_ptr` instruction with an `as` instruction and repurpose
// it as the break operand.
// This corresponds to similar code in `setCondBrPayloadElideBlockStorePtr`.
if (block_scope.rl_ty_inst != .none) {
for (block_scope.labeled_breaks.items) |br| {
// We expect the `store_to_block_ptr` to be created between 1-3 instructions
// prior to the break.
var search_index = br -| 3;
while (search_index < br) : (search_index += 1) {
if (zir_tags[search_index] == .store_to_block_ptr and
zir_datas[search_index].bin.lhs == block_scope.rl_ptr)
{
zir_tags[search_index] = .as;
zir_datas[search_index].bin = .{
.lhs = block_scope.rl_ty_inst,
.rhs = zir_datas[br].@"break".operand,
};
zir_datas[br].@"break".operand = indexToRef(search_index);
break;
}
} else unreachable;
}
}
try block_scope.setBlockBody(block_inst);
const block_ref = indexToRef(block_inst);
switch (rl) {
@@ -5366,6 +5392,7 @@ fn setCondBrPayloadElideBlockStorePtr(
// switch's result location is a `ty`. In this case we overwrite the
// `store_to_block_ptr` instruction with an `as` instruction and repurpose
// it as the break operand.
// This corresponds to similar code in `labeledBlockExpr`.
for (then_body) |src_inst| {
if (zir_tags[src_inst] == .store_to_block_ptr and
zir_datas[src_inst].bin.lhs == block_ptr)

12
test/behavior/basic.zig
View File

@@ -875,3 +875,15 @@ test "catch in block has correct result location" {
};
try expect(config_h_text == 1);
}
test "labeled block with runtime branch forwards its result location type to break statements" {
const E = enum { a, b };
var a = false;
const e: E = blk: {
if (a) {
break :blk .a;
}
break :blk .b;
};
try expect(e == .b);
}