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Refactor subpattern logic out of Context (#4929)

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Note this is building on #4927 which factors out RegionStack, because
this heavily uses the region stack. However, it's a more complex level
of logic that appears specific to pattern handling.

I've moved InsertHere to pattern_match.cpp because it appears to be in
specific use there.
This commit is contained in:
Jon Ross-Perkins
2025-02-12 19:14:37 +00:00
committed by GitHub
parent d6ce8f192d
commit 71c91eaf14
9 changed files with 138 additions and 107 deletions
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toolchain/check/pattern_match.cpp
+48 -1
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@@ -12,6 +12,7 @@
#include "toolchain/base/kind_switch.h"
#include "toolchain/check/context.h"
#include "toolchain/check/convert.h"
#include "toolchain/check/subpattern.h"
namespace Carbon::Check {
@@ -124,6 +125,52 @@ auto MatchContext::DoWork(Context& context) -> SemIR::InstBlockId {
return block_id;
}
// Inserts the given region into the current code block. If the region
// consists of a single block, this will be implemented as a `splice_block`
// inst. Otherwise, this will end the current block with a branch to the entry
// block of the region, and add future insts to a new block which is the
// immediate successor of the region's exit block. As a result, this cannot be
// called more than once for the same region.
static auto InsertHere(Context& context, SemIR::ExprRegionId region_id)
-> SemIR::InstId {
auto region = context.sem_ir().expr_regions().Get(region_id);
auto loc_id = context.insts().GetLocId(region.result_id);
auto exit_block = context.inst_blocks().Get(region.block_ids.back());
if (region.block_ids.size() == 1) {
// TODO: Is it possible to avoid leaving an "orphan" block in the IR in the
// first two cases?
if (exit_block.empty()) {
return region.result_id;
}
if (exit_block.size() == 1) {
context.inst_block_stack().AddInstId(exit_block.front());
return region.result_id;
}
return context.AddInst<SemIR::SpliceBlock>(
loc_id, {.type_id = context.insts().Get(region.result_id).type_id(),
.block_id = region.block_ids.front(),
.result_id = region.result_id});
}
if (context.region_stack().empty()) {
context.TODO(loc_id,
"Control flow expressions are currently only supported inside "
"functions.");
return SemIR::ErrorInst::SingletonInstId;
}
context.AddInst(SemIR::LocIdAndInst::NoLoc<SemIR::Branch>(
{.target_id = region.block_ids.front()}));
context.inst_block_stack().Pop();
// TODO: this will cumulatively cost O(MN) running time for M blocks
// at the Nth level of the stack. Figure out how to do better.
context.region_stack().AddToRegion(region.block_ids);
auto resume_with_block_id =
context.insts().GetAs<SemIR::Branch>(exit_block.back()).target_id;
CARBON_CHECK(context.inst_blocks().GetOrEmpty(resume_with_block_id).empty());
context.inst_block_stack().Push(resume_with_block_id);
context.region_stack().AddToRegion(resume_with_block_id, loc_id);
return region.result_id;
}
auto MatchContext::EmitPatternMatch(Context& context,
MatchContext::WorkItem entry) -> void {
if (entry.pattern_id == SemIR::ErrorInst::SingletonInstId) {
@@ -149,7 +196,7 @@ auto MatchContext::EmitPatternMatch(Context& context,
context.bind_name_map().Lookup(entry.pattern_id).value(),
{.bind_name_id = SemIR::InstId::None,
.type_expr_region_id = SemIR::ExprRegionId::None});
context.InsertHere(type_expr_region_id);
InsertHere(context, type_expr_region_id);
auto value_id = entry.scrutinee_id;
switch (kind_) {
case MatchKind::Local: {