Fix a bug with hoisting 'IRVar' insts that are used outside the loop #6446
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- We introduce a 'CheckpointObject' inst and use that to split loop state insts into two pieces (one for within-loop uses and one for outside-loop uses. - This allows the two kinds of uses to be handled separately by the hoisting mechanism - CheckpointObject is then lowered to a no-op after hoisting is complete.
csyonghe
reviewed
Feb 24, 2025
| { | ||
| setInsertAfterOrdinaryInst(&builder, inst); | ||
| auto copy = builder.emitCheckpointObject(inst); | ||
| copy->sourceLoc = inst->sourceLoc; // Copy source location so that checkpoint |
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long multiline comment should be placed before the line.
| HashSet<IRUse*> afterLoopUses; | ||
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| // Get the indices for the condition block | ||
| auto condBlockIndices = indexedBlockInfo.getValue(condBlock); |
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I want us to be extra careful when using List types inside loops like this. The code here would be alloc/free-ing memory like crazy just to represent the temporary list objects. Should return and use references if indexedBlockInfo is immutable in this loop.
| // Shouldn't see any vars. | ||
| SLANG_ASSERT(!as<IRVar>(inst)); | ||
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| HashSet<IRUse*> loopUses; |
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any reason to use HashSet? it seems List would suffice.
also move these outside of the loop, and do a loopUses.clear() here to avoid frequent alloc.
csyonghe
approved these changes
Feb 25, 2025
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OpCheckpointObjectis then lowered to a no-op after hoisting is complete.Also added a test to check for this.
Fixes: #6394 and #5999