[Mlir-commits] [mlir] [mlir][linalg] Support subtracting accumulation in partial reduction … (PR #214033)

[Federico Bruzzone]

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@@ -534,6 +535,78 @@ static InitSliceInfo getInitSliceInfo(MLIRContext *context,
       partialReductionMap, initOperandShape);
 }
 
+/// Returns true if `combinerOp` accumulates into `accumulator` by subtracting
+/// the reduced value from it, i.e. it reduces the negated inputs.
+///
+/// Subtraction is not commutative, so the accumulator has to be the left-hand
+/// side: `x - acc` computes an alternating sum instead of accumulating every
+/// input with the same sign, and cannot be split into partial results.
+static bool isSubtractingAccumulation(Operation *combinerOp,
+                                      Value accumulator) {
+  if (!isa<arith::SubFOp, arith::SubIOp>(combinerOp))
+    return false;
+  return combinerOp->getOperand(0) == accumulator;
+}
+
+/// Creates the operation combining two partial results of the subtracting
+/// accumulation performed by `combinerOp`, preserving its fast-math flags,
+/// rounding mode and integer overflow flags.
+///
+/// Note that the overflow flags assert that the original accumulation does not
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FedericoBruzzone wrote:

+1

https://github.com/llvm/llvm-project/pull/214033