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[mlir][index] Fold cmp(x, x) when x isn't a constant #78812

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Merged
merged 1 commit into from
Jan 19, 2024
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[mlir][index] Fold cmp(x, x) when x isn't a constant #78812

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22 changes: 22 additions & 0 deletions mlir/lib/Dialect/Index/IR/IndexOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -578,6 +578,24 @@ static std::optional<bool> foldCmpOfMaxOrMin(Operation *lhsOp,
lhsRange, ConstantIntRanges::constant(cstB));
}

/// Return the result of `cmp(pred, x, x)`
static bool compareSameArgs(IndexCmpPredicate pred) {
switch (pred) {
case IndexCmpPredicate::EQ:
case IndexCmpPredicate::SGE:
case IndexCmpPredicate::SLE:
case IndexCmpPredicate::UGE:
case IndexCmpPredicate::ULE:
return true;
case IndexCmpPredicate::NE:
case IndexCmpPredicate::SGT:
case IndexCmpPredicate::SLT:
case IndexCmpPredicate::UGT:
case IndexCmpPredicate::ULT:
return false;
}
}

OpFoldResult CmpOp::fold(FoldAdaptor adaptor) {
// Attempt to fold if both inputs are constant.
auto lhs = dyn_cast_if_present<IntegerAttr>(adaptor.getLhs());
Expand Down Expand Up @@ -606,6 +624,10 @@ OpFoldResult CmpOp::fold(FoldAdaptor adaptor) {
return BoolAttr::get(getContext(), *result64);
}

// Fold `cmp(x, x)`
if (getLhs() == getRhs())
return BoolAttr::get(getContext(), compareSameArgs(getPred()));

return {};
}

Expand Down
20 changes: 20 additions & 0 deletions mlir/test/Dialect/Index/index-canonicalize.mlir
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Expand Up @@ -499,6 +499,26 @@ func.func @cmp(%arg0: index) -> (i1, i1, i1, i1, i1, i1) {
return %0, %1, %2, %3, %5, %7 : i1, i1, i1, i1, i1, i1
}

// CHECK-LABEL: @cmp_same_args
func.func @cmp_same_args(%a: index) -> (i1, i1, i1, i1, i1, i1, i1, i1, i1, i1) {
%0 = index.cmp eq(%a, %a)
%1 = index.cmp sge(%a, %a)
%2 = index.cmp sle(%a, %a)
%3 = index.cmp uge(%a, %a)
%4 = index.cmp ule(%a, %a)
%5 = index.cmp ne(%a, %a)
%6 = index.cmp sgt(%a, %a)
%7 = index.cmp slt(%a, %a)
%8 = index.cmp ugt(%a, %a)
%9 = index.cmp ult(%a, %a)

// CHECK-DAG: %[[TRUE:.*]] = index.bool.constant true
// CHECK-DAG: %[[FALSE:.*]] = index.bool.constant false
// CHECK-NEXT: return %[[TRUE]], %[[TRUE]], %[[TRUE]], %[[TRUE]], %[[TRUE]],
// CHECK-SAME: %[[FALSE]], %[[FALSE]], %[[FALSE]], %[[FALSE]], %[[FALSE]]
return %0, %1, %2, %3, %4, %5, %6, %7, %8, %9 : i1, i1, i1, i1, i1, i1, i1, i1, i1, i1
}

// CHECK-LABEL: @cmp_nofold
func.func @cmp_nofold() -> i1 {
%lhs = index.constant 1
Expand Down