[llvm] [GlobalISel] Fix buildCopyFromRegs for split vectors (PR #77448)

[Pierre van Houtryve via llvm-commits]

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@@ -478,9 +478,43 @@ static void buildCopyFromRegs(MachineIRBuilder &B, ArrayRef<Register> OrigRegs,
   } else {
     // Vector was split, and elements promoted to a wider type.
     // FIXME: Should handle floating point promotions.
-    LLT BVType = LLT::fixed_vector(LLTy.getNumElements(), PartLLT);
-    auto BV = B.buildBuildVector(BVType, Regs);
-    B.buildTrunc(OrigRegs[0], BV);
+    unsigned NumElts = LLTy.getNumElements();
+    LLT BVType = LLT::fixed_vector(NumElts, PartLLT);
+
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Pierre-vh wrote:

I don't think so, I don't see how it could help because we have multiple Regs to process + we have to handle the anyExt

https://github.com/llvm/llvm-project/pull/77448