scf.for fix when iter-args and result args have shadow mismatch in fwd#2750
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scf.for fix when iter-args and result args have shadow mismatch in fwd#2750spikerheado1234 wants to merge 1 commit intomainfrom
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wsmoses
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Mar 18, 2026
| llvm::enumerate(targetValues, operandRange)) { | ||
| if (gutils->isConstantValue(regionValue)) | ||
| bool iterArgActive = !gutils->isConstantValue(regionValue); | ||
| bool resultActive = i < op->getNumResults() && |
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this isn't generally correct since an input operand doesn't necessarily correspond to the outputs as here.
Instead really you need to construct this correctly [and separately] for scf for, or with an interface -- and pass said array to the general controlFlowForwardHandler which accepts arrays
wsmoses
reviewed
Mar 18, 2026
| // | ||
| // We also register the mapping in invertedPointers so that invertPointerM, | ||
| // which checks invertedPointers before isConstantValue, returns the shadow | ||
| // block arg instead of zero when body ops reference this iter arg. |
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this should be handled in createWithShadows, not here
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In forward mode AD, if an iter-arg is deemed a constant, yet its corresponding result has a tangent, then there will be a mismatch between the number of iter-args and result-args. This PR fixes that by unioning if either an iter-arg or its corresponding result is active, inserting a corresponding shadow arg if at least one is active.