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[TableGen] Resolve arguments with fields in records #107829

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[TableGen] Resolve arguments with fields in records #107829

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5 changes: 4 additions & 1 deletion llvm/include/llvm/TableGen/Record.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2289,9 +2289,12 @@ class RecordResolver final : public Resolver {
DenseMap<Init *, Init *> Cache;
SmallVector<Init *, 4> Stack;
Init *Name = nullptr;
// Cache is for fields, ArgumentResolver is for arguments.
MapResolver *ArgumentResolver;

public:
explicit RecordResolver(Record &R) : Resolver(&R) {}
explicit RecordResolver(Record &R, MapResolver *ArgumentResolver = nullptr)
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Is it possible to just make this a required field?

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@optimisan optimisan Sep 16, 2024 •
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Yes, that would be ideal since the two-step resolution happens everywhere (in def R : C<n> as well).

This limitation of inaccessible arguments has forced the !if resolution to forego short-circuiting and resolve the MHS and RHS regardless of the condition. And so, the following case fails with a stack overflow:

class C<int n> {
    int v = n; 
    // !if ignores v==0 and evaluates C<n-1>.ret everytime
    // Ideally should short-circuit to 3
    int ret = !if(!eq(v, 0), 3, C<!sub(n, 1)>.ret);
}
def R : C<0>;

I think Record should contain arguments from each sub-class along with their fields as usual. Will see how that goes. With that, this patch would not be necessary since Record itself would have access to its arguments.

: Resolver(&R), ArgumentResolver(ArgumentResolver) {}

void setName(Init *NewName) { Name = NewName; }

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12 changes: 9 additions & 3 deletions llvm/lib/TableGen/Record.cpp
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Expand Up @@ -2321,8 +2321,6 @@ DefInit *VarDefInit::instantiate() {
R.set(Arg->getName(), Arg->getValue());
}

NewRec->resolveReferences(R);

// Add superclasses.
ArrayRef<std::pair<Record *, SMRange>> SCs = Class->getSuperClasses();
for (const auto &SCPair : SCs)
Expand All @@ -2332,7 +2330,10 @@ DefInit *VarDefInit::instantiate() {
Class, SMRange(Class->getLoc().back(), Class->getLoc().back()));

// Resolve internal references and store in record keeper
NewRec->resolveReferences();
RecordResolver RR(*NewRec, &R);
RR.setFinal(true);
NewRec->resolveReferences(RR);

Records.addDef(std::move(NewRecOwner));

// Check the assertions.
Expand Down Expand Up @@ -3348,6 +3349,11 @@ Init *RecordResolver::resolve(Init *VarName) {
if (Val)
return Val;

if (ArgumentResolver && (Val = ArgumentResolver->resolve(VarName))) {
Cache[VarName] = Val;
return Val;
}

if (llvm::is_contained(Stack, VarName))
return nullptr; // prevent infinite recursion

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11 changes: 11 additions & 0 deletions llvm/test/TableGen/record-recursion.td
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@@ -0,0 +1,11 @@
// RUN: llvm-tblgen %s | FileCheck %s

class SumTillN<int n> {
int v = !add(n, 0);
int ret = !if(!gt(v, 0), !add(v, SumTillN<!sub(n, 1)>.ret), v);
}

// CHECK: def SumTill4
// CHECK-NEXT: int v = 3;
// CHECK-NEXT: int ret = 6;
def SumTill4 : SumTillN<3>;
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