[Mlir-commits] [mlir] [mlir] [arith] Combine op for select (PR #234818)

[Renato Golin]

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@@ -3128,6 +3130,119 @@ struct SelectToExtUI : public OpRewritePattern<arith::SelectOp> {
   }
 };
 
+///   select(c, F(a0, a1), F(b0, b1))
+///     -> F(select(c, a0, b0), select(c, a1, b1)).
+/// For a non-poison condition, each lane of F receives exactly the operands of
+/// the selected producer, so poison in the other producer remains masked. For
+/// a poison condition, the original result is poison; the replacement may
+/// refine it, but must not introduce immediate undefined behavior. In
+/// particular, speculatability must also hold with the new operands.
+struct SelectCommonElementwiseOp : public OpRewritePattern<arith::SelectOp> {
+  using Base::Base;
+
+  LogicalResult matchAndRewrite(arith::SelectOp op,
+                                PatternRewriter &rewriter) const override {
+    Operation *lhs = op.getTrueValue().getDefiningOp();
+    Operation *rhs = op.getFalseValue().getDefiningOp();
+    if (!lhs || !rhs || lhs == rhs)
+      return failure();
+
+    for (Operation *producer : {lhs, rhs}) {
+      // Conservative design. The motivation is we don't want to transfer:
+      //
+      //  x = F(a)
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rengolin wrote:

this code really isn't necessary

https://github.com/llvm/llvm-project/pull/234818