[llvm] [SandboxVec][BottomUpVec] Add cost estimation and tr-accept-or-revert pass (PR #126325)

[via llvm-commits]

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@@ -448,13 +449,24 @@ bool BottomUpVec::runOnFunction(Function &F, const Analyses &A) {
 
           assert(SeedSlice.size() >= 2 && "Should have been rejected!");
 
-          // TODO: If vectorization succeeds, run the RegionPassManager on the
-          // resulting region.
-
           // TODO: Refactor to remove the unnecessary copy to SeedSliceVals.
           SmallVector<Value *> SeedSliceVals(SeedSlice.begin(),
                                              SeedSlice.end());
-          Change |= tryVectorize(SeedSliceVals);
+          // Create an empty region. Instructions get added to the region
+          // automatically by the callbacks.
+          auto &Ctx = F.getContext();
+          Region Rgn(Ctx, A.getTTI());
+          // Save the state of the IR before we make any changes. The
+          // transaction gets accepted/reverted by the tr-accept-or-revert pass.
+          Ctx.save();
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vporpo wrote:

Yes, this asymmetry will go away in a follow-up patch.

https://github.com/llvm/llvm-project/pull/126325