[Mlir-commits] [mlir] [MLIR] Fuse locations of hoisted / merged constants (PR #74670)

[Mehdi Amini]

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@@ -19,6 +19,38 @@
 
 using namespace mlir;
 
+// Fuse `foldedLocation` into the Location of `retainedOp`.
+// This will result in `retainedOp` having a FusedLoc with a StringAttr tag
+// "OpFold" to help trace the source of the fusion. If `retainedOp` already had
+// a FusedLoc with the same tag, `foldedLocation` will simply be appended to it.
+// Usage:
+// - When an op is deduplicated, fuse the location of the op to be removed into
+//   the op that is retained.
+// - When an op is hoisted to the front/back of a block, fuse the location of
+//   the parent region of the block into the hoisted op.
+static void appendFoldedLocation(Operation *retainedOp,
+                                 Location foldedLocation) {
+  constexpr std::string_view tag = "OpFold";
+  // Append into existing fused location if it has the same tag.
+  if (auto existingFusedLoc =
+          retainedOp->getLoc().dyn_cast<FusedLocWith<StringAttr>>()) {
+    StringAttr existingMetadata = existingFusedLoc.getMetadata();
+    if (existingMetadata.strref().equals(tag)) {
+      SmallVector<Location> locations(existingFusedLoc.getLocations());
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joker-eph wrote:

It this possible we'd fuse the same location over and over? Should this be a SmallPtrSet to remove the duplication?

Please add tests for this.

https://github.com/llvm/llvm-project/pull/74670