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AstGen: improve switch expressions

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* use the proper result location strategy even when there are noreturn
   prongs in the switch expression
 * when using break_operand strategy, actually omit the
   store_to_block_ptr instructions rather than eliding them.
 * for both strategies, properly handle noreturn prongs.
This commit is contained in:
Andrew Kelley 2021-03-31 12:37:20 -07:00
parent 549af582e7
commit c7b09be8de
1 changed files with 87 additions and 42 deletions
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129
src/AstGen.zig
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@ -2752,9 +2752,9 @@ fn switchExpr(
};
break :blk &capture_val_scope.base;
};
block_scope.break_count += 1;
const case_result = try expr(&case_scope, sub_scope, block_scope.break_result_loc, case.ast.target_expr);
if (!astgen.refIsNoReturn(case_result)) {
block_scope.break_count += 1;
_ = try case_scope.addBreak(.@"break", switch_block, case_result);
}
// Documentation for this: `zir.Inst.SwitchBlock` and `zir.Inst.SwitchBlockMulti`.
@ -2873,9 +2873,9 @@ fn switchExpr(
});
}
block_scope.break_count += 1;
const case_result = try expr(&case_scope, sub_scope, block_scope.break_result_loc, case.ast.target_expr);
if (!astgen.refIsNoReturn(case_result)) {
block_scope.break_count += 1;
_ = try case_scope.addBreak(.@"break", switch_block, case_result);
}
@ -2886,9 +2886,9 @@ fn switchExpr(
} else {
const item_node = case.ast.values[0];
const item_inst = try comptimeExpr(parent_gz, scope, item_rl, item_node);
block_scope.break_count += 1;
const case_result = try expr(&case_scope, sub_scope, block_scope.break_result_loc, case.ast.target_expr);
if (!astgen.refIsNoReturn(case_result)) {
block_scope.break_count += 1;
_ = try case_scope.addBreak(.@"break", switch_block, case_result);
}
try scalar_cases_payload.ensureCapacity(gpa, scalar_cases_payload.items.len +
@ -2925,13 +2925,11 @@ fn switchExpr(
0b1_10_1 => .switch_block_ref_under_multi,
else => unreachable,
};
const zir_datas = astgen.instructions.items(.data);
const payload_index = astgen.extra.items.len;
const zir_datas = astgen.instructions.items(.data);
zir_datas[switch_block].pl_node.payload_index = @intCast(u32, payload_index);
try astgen.extra.ensureCapacity(gpa, astgen.extra.items.len +
scalar_cases_payload.items.len + multi_cases_payload.items.len);
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items);
astgen.extra.appendSliceAssumeCapacity(multi_cases_payload.items);
const strat = rl.strategy(&block_scope);
switch (strat.tag) {
.break_operand => {
@ -2939,51 +2937,90 @@ fn switchExpr(
// this is always true.
assert(strat.elide_store_to_block_ptr_instructions);
// There will necessarily be a store_to_block_ptr for
// all prongs, except for prongs that ended with a noreturn instruction.
// Elide all the `store_to_block_ptr` instructions.
var extra_index: usize = payload_index;
var extra_index: usize = 0;
extra_index += 2;
extra_index += @boolToInt(multi_cases_len != 0);
if (special_prong != .none) {
const body_len = astgen.extra.items[extra_index];
const body_len_index = extra_index;
const body_len = scalar_cases_payload.items[extra_index];
extra_index += 1;
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const store_inst = body[body.len - 2];
assert(zir_tags[store_inst] == .store_to_block_ptr);
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
zir_tags[store_inst] = .elided;
zir_datas[store_inst] = undefined;
extra_index += body_len - 2;
const store_inst = scalar_cases_payload.items[extra_index];
if (zir_tags[store_inst] == .store_to_block_ptr) {
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
scalar_cases_payload.items[body_len_index] -= 1;
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[0..extra_index]);
extra_index += 1;
astgen.extra.appendAssumeCapacity(scalar_cases_payload.items[extra_index]);
extra_index += 1;
} else {
extra_index += 2;
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[0..extra_index]);
}
} else {
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[0..extra_index]);
}
var scalar_i: u32 = 0;
while (scalar_i < scalar_cases_len) : (scalar_i += 1) {
const start_index = extra_index;
extra_index += 1;
const body_len = astgen.extra.items[extra_index];
const body_len_index = extra_index;
const body_len = scalar_cases_payload.items[extra_index];
extra_index += 1;
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const store_inst = body[body.len - 2];
assert(zir_tags[store_inst] == .store_to_block_ptr);
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
zir_tags[store_inst] = .elided;
zir_datas[store_inst] = undefined;
if (body_len < 2) {
extra_index += body_len;
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[start_index..extra_index]);
continue;
}
extra_index += body_len - 2;
const store_inst = scalar_cases_payload.items[extra_index];
if (zir_tags[store_inst] == .store_to_block_ptr) {
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
scalar_cases_payload.items[body_len_index] -= 1;
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[start_index..extra_index]);
extra_index += 1;
astgen.extra.appendAssumeCapacity(scalar_cases_payload.items[extra_index]);
extra_index += 1;
} else {
extra_index += 2;
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items[start_index..extra_index]);
}
}
extra_index = 0;
var multi_i: u32 = 0;
while (multi_i < multi_cases_len) : (multi_i += 1) {
const items_len = astgen.extra.items[extra_index];
const start_index = extra_index;
const items_len = multi_cases_payload.items[extra_index];
extra_index += 1;
const ranges_len = astgen.extra.items[extra_index];
const ranges_len = multi_cases_payload.items[extra_index];
extra_index += 1;
const body_len = astgen.extra.items[extra_index];
const body_len_index = extra_index;
const body_len = multi_cases_payload.items[extra_index];
extra_index += 1;
extra_index += items_len;
extra_index += 2 * ranges_len;
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const store_inst = body[body.len - 2];
assert(zir_tags[store_inst] == .store_to_block_ptr);
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
zir_tags[store_inst] = .elided;
zir_datas[store_inst] = undefined;
if (body_len < 2) {
extra_index += body_len;
astgen.extra.appendSliceAssumeCapacity(multi_cases_payload.items[start_index..extra_index]);
continue;
}
extra_index += body_len - 2;
const store_inst = multi_cases_payload.items[extra_index];
if (zir_tags[store_inst] == .store_to_block_ptr) {
assert(zir_datas[store_inst].bin.lhs == block_scope.rl_ptr);
multi_cases_payload.items[body_len_index] -= 1;
astgen.extra.appendSliceAssumeCapacity(multi_cases_payload.items[start_index..extra_index]);
extra_index += 1;
astgen.extra.appendAssumeCapacity(multi_cases_payload.items[extra_index]);
extra_index += 1;
} else {
extra_index += 2;
astgen.extra.appendSliceAssumeCapacity(multi_cases_payload.items[start_index..extra_index]);
}
}
const block_ref = astgen.indexToRef(switch_block);
@ -2994,6 +3031,8 @@ fn switchExpr(
},
.break_void => {
assert(!strat.elide_store_to_block_ptr_instructions);
astgen.extra.appendSliceAssumeCapacity(scalar_cases_payload.items);
astgen.extra.appendSliceAssumeCapacity(multi_cases_payload.items);
// Modify all the terminating instruction tags to become `break` variants.
var extra_index: usize = payload_index;
extra_index += 2;
@ -3004,9 +3043,11 @@ fn switchExpr(
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const last = body[body.len - 1];
assert(zir_tags[last] == .@"break");
assert(zir_datas[last].@"break".block_inst == switch_block);
zir_datas[last].@"break".operand = .void_value;
if (zir_tags[last] == .@"break" and
zir_datas[last].@"break".block_inst == switch_block)
{
zir_datas[last].@"break".operand = .void_value;
}
}
var scalar_i: u32 = 0;
while (scalar_i < scalar_cases_len) : (scalar_i += 1) {
@ -3016,9 +3057,11 @@ fn switchExpr(
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const last = body[body.len - 1];
assert(zir_tags[last] == .@"break");
assert(zir_datas[last].@"break".block_inst == switch_block);
zir_datas[last].@"break".operand = .void_value;
if (zir_tags[last] == .@"break" and
zir_datas[last].@"break".block_inst == switch_block)
{
zir_datas[last].@"break".operand = .void_value;
}
}
var multi_i: u32 = 0;
while (multi_i < multi_cases_len) : (multi_i += 1) {
@ -3033,9 +3076,11 @@ fn switchExpr(
const body = astgen.extra.items[extra_index..][0..body_len];
extra_index += body_len;
const last = body[body.len - 1];
assert(zir_tags[last] == .@"break");
assert(zir_datas[last].@"break".block_inst == switch_block);
zir_datas[last].@"break".operand = .void_value;
if (zir_tags[last] == .@"break" and
zir_datas[last].@"break".block_inst == switch_block)
{
zir_datas[last].@"break".operand = .void_value;
}
}
return astgen.indexToRef(switch_block);