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CommonCompareExpressionRewrite: place the negation after the op it reads #2995

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CommonCompareExpressionRewrite: place the negation after the op it reads #2995

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4 changes: 4 additions & 0 deletions src/enzyme_ad/jax/Passes/EnzymeHLOOpt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21918,6 +21918,10 @@ struct CommonCompareExpressionRewrite
rewriter.replaceOp(op, negatedCondition);
return success();
} else {
// The negation reads op's result, so it must sit after op — the
// rewriter's insertion point is before op here.
PatternRewriter::InsertionGuard guard(rewriter);
rewriter.setInsertionPoint(user);
auto negatedCondition = stablehlo::NotOp::create(
rewriter, userCompareOp.getLoc(), op.getResult());
rewriter.replaceOp(user, negatedCondition);
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15 changes: 15 additions & 0 deletions test/lit_tests/commoncompare_neg_after.mlir
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@@ -0,0 +1,15 @@
// RUN: enzymexlamlir-opt %s --enzyme-hlo-opt | FileCheck %s

// The negated twin appears after the matched compare: the rewrite replaces
// it with a negation of the earlier compare, which must be inserted after
// the compare it reads, not at the match point before it.
func.func @negpair(%a: tensor<4xi32>, %b: tensor<4xi32>) -> (tensor<4xi1>, tensor<4xi1>) {
%le = stablehlo.compare LE, %a, %b, SIGNED : (tensor<4xi32>, tensor<4xi32>) -> tensor<4xi1>
%gt = stablehlo.compare GT, %a, %b, SIGNED : (tensor<4xi32>, tensor<4xi32>) -> tensor<4xi1>
return %le, %gt : tensor<4xi1>, tensor<4xi1>
}

// CHECK-LABEL: func.func @negpair(
// CHECK-NEXT: %[[LE:.+]] = stablehlo.compare LE, %arg0, %arg1, SIGNED
// CHECK-NEXT: %[[NOT:.+]] = stablehlo.not %[[LE]]
// CHECK-NEXT: return %[[LE]], %[[NOT]]
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