[llvm] [SROA] Prevent load atomic vector from being generated (PR #112432)

[Matt Arsenault via llvm-commits]

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@@ -2853,6 +2853,11 @@ class AllocaSliceRewriter : public InstVisitor<AllocaSliceRewriter, bool> {
 
   bool visitLoadInst(LoadInst &LI) {
     LLVM_DEBUG(dbgs() << "    original: " << LI << "\n");
+
+    // load atomic vector would be generated, which is illegal
+    if (LI.isAtomic() && NewAI.getAllocatedType()->isVectorTy())
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arsenm wrote:

No, you need to ensure the atomic is a valid type for an atomic load. 

Alternatively you can do the load with the equivalent sized type and then bitcast (which is why this restriction is dumb in the first place, the lowering can always do the same) 

https://github.com/llvm/llvm-project/pull/112432