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[AutoDiff] Better diagnose non-differentiability for throwing functions #81669

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Merged
merged 1 commit into from
May 21, 2025
Merged

[AutoDiff] Better diagnose non-differentiability for throwing functions #81669

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25 changes: 21 additions & 4 deletions lib/SILOptimizer/Differentiation/PullbackCloner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1780,8 +1780,12 @@ class PullbackCloner::Implementation final
void visitMoveValueInst(MoveValueInst *mvi) {
switch (getTangentValueCategory(mvi)) {
case SILValueCategory::Address:
llvm::report_fatal_error("AutoDiff does not support move_value with "
"SILValueCategory::Address");
LLVM_DEBUG(getADDebugStream() << "AutoDiff does not support move_value with "
"SILValueCategory::Address");
getContext().emitNondifferentiabilityError(
mvi, getInvoker(), diag::autodiff_expression_not_differentiable_note);
errorOccurred = true;
return;
case SILValueCategory::Object:
visitValueOwnershipInst(mvi, /*needZeroResAdj=*/true);
}
Expand Down Expand Up @@ -3121,8 +3125,21 @@ void PullbackCloner::Implementation::visitSILBasicBlock(SILBasicBlock *bb) {
break;
}
}
} else
llvm::report_fatal_error("do not know how to handle this incoming bb argument");
} else {
LLVM_DEBUG(getADDebugStream() <<
"do not know how to handle this incoming bb argument");
if (auto term = bbArg->getSingleTerminator()) {
getContext().emitNondifferentiabilityError(term, getInvoker(),
diag::autodiff_expression_not_differentiable_note);
} else {
// This will be a bit confusing, but still better than nothing.
getContext().emitNondifferentiabilityError(bbArg, getInvoker(),
diag::autodiff_expression_not_differentiable_note);
}

errorOccurred = true;
return;
}
}

// 3. Build the pullback successor cases for the `switch_enum`
Expand Down
11 changes: 11 additions & 0 deletions test/AutoDiff/SILOptimizer/differentiation_diagnostics.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,17 @@ func try_apply_rethrows(_ x: Float) -> Float {
return x
}

// This generates `try_apply` which we do not know to handle yet, therefore
// one should use a.differentialMap here. If / when differentiation of throwing
// functions will be supported, we'd need to remove this diagnostics.
// expected-error @+2 {{function is not differentiable}}
// expected-note @+2 {{when differentiating this function definition}}
@differentiable(reverse)
func map_nondiff(_ a: [Float]) -> [Float] {
// expected-note @+1 {{expression is not differentiable}}
return a.map { $0 }
}

//===----------------------------------------------------------------------===//
// Unreachable
//===----------------------------------------------------------------------===//
Expand Down