[Mlir-commits] [mlir] [mlir][Vector] add vector.insert canonicalization pattern for vectors created from ub.poison (PR #142944)

[Yang Bai]

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@@ -3250,6 +3262,128 @@ class InsertSplatToSplat final : public OpRewritePattern<InsertOp> {
     return success();
   }
 };
+
+/// Pattern to optimize a chain of insertions.
+///
+/// This pattern identifies chains of vector.insert operations that:
+/// 1. Only insert values at static positions.
+/// 2. Completely initialize all elements in the resulting vector.
+/// 3. All intermediate insert operations have only one use.
+///
+/// When these conditions are met, the entire chain can be replaced with a
+/// single vector.from_elements operation.
+///
+/// Example transformation:
+///   %poison = ub.poison : vector<2xi32>
+///   %0 = vector.insert %c1, %poison[0] : i32 into vector<2xi32>
+///   %1 = vector.insert %c2, %0[1] : i32 into vector<2xi32>
+/// ->
+///   %result = vector.from_elements %c1, %c2 : vector<2xi32>
+class InsertChainFullyInitialized final : public OpRewritePattern<InsertOp> {
+public:
+  using OpRewritePattern::OpRewritePattern;
+  LogicalResult matchAndRewrite(InsertOp op,
+                                PatternRewriter &rewriter) const override {
+
+    VectorType destTy = op.getDestVectorType();
+    if (destTy.isScalable())
+      return failure();
+    // Check if the result is used as the dest operand of another vector.insert
+    // Only care about the last op in a chain of insertions.
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yangtetris wrote:

That makes sense. Document updated.

https://github.com/llvm/llvm-project/pull/142944