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[maglev] Fix DCHECK in RegisterMerge with constants

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Merging register values can encounter constants, which are loadable but
don't have spill slots. Add support for these (in practice this is the
same behaviour, we're just fixing a DCHECK).

Bug: v8:7700
Change-Id: I9ab8ba1fc3a3a64fe16668bb317ad02f878f5849
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3749579
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81611}
This commit is contained in:
Leszek Swirski 2022-07-08 12:25:29 +02:00 committed by V8 LUCI CQ
parent 307dffed3c
commit 871ed8cf08
2 changed files with 10 additions and 7 deletions
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9
src/maglev/maglev-ir.h
View File

@ -815,9 +815,14 @@ class ValueNode : public Node {
}
compiler::AllocatedOperand spill_slot() const {
DCHECK_EQ(state_, kSpillOrHint);
DCHECK(is_spilled());
return compiler::AllocatedOperand::cast(spill_or_hint_);
return compiler::AllocatedOperand::cast(loadable_slot());
}
compiler::InstructionOperand loadable_slot() const {
DCHECK_EQ(state_, kSpillOrHint);
DCHECK(is_loadable());
return spill_or_hint_;
}
void mark_use(NodeIdT id, InputLocation* input_location) {

8
src/maglev/maglev-regalloc.cc
View File

@ -1527,12 +1527,10 @@ void StraightForwardRegisterAllocator::MergeRegisterValues(ControlNode* control,
merge->node = node == nullptr ? incoming : node;
// If the register is unallocated at the merge point, allocation so far
// is the spill slot for the incoming value. Otherwise all incoming
// is the loadable slot for the incoming value. Otherwise all incoming
// branches agree that the current node is in the register info.
compiler::AllocatedOperand info_so_far =
node == nullptr
? compiler::AllocatedOperand::cast(incoming->spill_slot())
: register_info;
compiler::InstructionOperand info_so_far =
node == nullptr ? incoming->loadable_slot() : register_info;
// Initialize the entire array with info_so_far since we don't know in
// which order we've seen the predecessors so far. Predecessors we