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[vm/compiler] Remove unnecessary type check from optimized switches

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Switch optimization now relies on static type of the tested value,
so it is safe to omit the type check (with sound null safety) or
reduce it to a null check (without sound null safety).

TEST=co19/LanguageFeatures/Patterns/Exhaustiveness/exhaustiveness_enum_A01_t01
Fixes https://github.com/dart-lang/sdk/issues/52422

Change-Id: Ic93f4f212bee9ed3bfe5035f3c8d7535274c2f63
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/304102
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
This commit is contained in:
Alexander Markov 2023-05-17 17:11:28 +00:00 committed by Commit Queue
parent 027d0738d0
commit 43ce5487c1
1 changed files with 18 additions and 21 deletions
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39
runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc
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@ -5072,30 +5072,23 @@ Fragment StreamingFlowGraphBuilder::BuildOptimizedSwitchPrelude(
SwitchHelper* helper,
JoinEntryInstr* join) {
const TokenPosition pos = helper->position();
// We need to check that the switch variable is of the correct type.
// If it is not, we go to [join] which is either the default case or
// the exit of the switch statement.
TargetEntryInstr* then_entry;
TargetEntryInstr* otherwise_entry;
const AbstractType& expression_type = helper->expression_type();
ASSERT(dart::SimpleInstanceOfType(expression_type));
Fragment instructions;
instructions += LoadLocal(scopes()->switch_variable);
instructions += Constant(expression_type);
instructions += InstanceCall(
pos, Library::PrivateCoreLibName(Symbols::_simpleInstanceOf()),
Token::kIS, /*argument_count=*/2,
/*checked_argument_count=*/2);
instructions += BranchIfTrue(&then_entry, &otherwise_entry, /*negate=*/false);
Fragment otherwise_instructions(otherwise_entry);
otherwise_instructions += Goto(join);
if (!IG->null_safety()) {
// Without sound null safety we need to check that the switch variable is
// not null. If it is null, we go to [join] which is either the default
// case or the exit of the switch statement.
TargetEntryInstr* null_entry;
TargetEntryInstr* non_null_entry;
instructions = Fragment(instructions.entry, then_entry);
instructions += LoadLocal(scopes()->switch_variable);
instructions += BranchIfNull(&null_entry, &non_null_entry);
Fragment null_instructions(null_entry);
null_instructions += Goto(join);
instructions = Fragment(instructions.entry, non_null_entry);
}
if (helper->is_enum_switch()) {
// For an enum switch, we need to load the enum index from the switch
@ -5260,6 +5253,10 @@ Fragment StreamingFlowGraphBuilder::BuildBinarySearchSwitch(
stack.Add(
SwitchRange::Branch(range.min(), middle, lower_branch_instructions));
}
if (current_instructions.is_empty()) {
current_instructions = branch_instructions;
}
}
return Fragment(current_instructions.entry, join_instructions.current);