[llvm] [Matrix] Place allocas in function entry. (PR #190032)

[Florian Hahn via llvm-commits]

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@@ -1950,14 +1952,16 @@ class LowerMatrixIntrinsics {
     setExplicitlyUnknownBranchWeightsIfProfiled(*BR2, DEBUG_TYPE);
 
     // Copy load operand to new alloca.
-    Builder.SetInsertPoint(Copy, Copy->begin());
     auto *VT = cast<FixedVectorType>(Load->getType());
     // Use an array type for the alloca, to avoid potentially huge alignment
     // requirements for large vector types.
     auto *ArrayTy = ArrayType::get(VT->getElementType(), VT->getNumElements());
+    IRBuilder<> AllocaBuilder(&Func.getEntryBlock().front());
     AllocaInst *Alloca =
-        Builder.CreateAlloca(ArrayTy, Load->getPointerAddressSpace());
+        AllocaBuilder.CreateAlloca(ArrayTy, Load->getPointerAddressSpace());
 
+    Builder.SetInsertPoint(Copy, Copy->begin());
+    Builder.CreateLifetimeStart(Alloca);
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fhahn wrote:

Sounds good, I updated the code to emit it before the conditional check, thanks

https://github.com/llvm/llvm-project/pull/190032