[llvm] [AMDGPU] Update base addr of dyn alloca considering GrowingUp stack (PR #119822)

[Sergei Barannikov via llvm-commits]

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@@ -4023,10 +4024,20 @@ SDValue SITargetLowering::lowerDYNAMIC_STACKALLOCImpl(SDValue Op,
   Chain = DAG.getCALLSEQ_START(Chain, 0, 0, dl);
 
   SDValue Size = Tmp2.getOperand(1);
-  SDValue SP = DAG.getCopyFromReg(Chain, dl, SPReg, VT);
-  Chain = SP.getValue(1);
+  SDValue SPOld = DAG.getCopyFromReg(Chain, dl, SPReg, VT);
+  Chain = SPOld.getValue(1);
   MaybeAlign Alignment = cast<ConstantSDNode>(Tmp3)->getMaybeAlignValue();
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s-barannikov wrote:

The alignment is guaranteed to be specified:
`Align Alignment = cast<ConstantSDNode>(Op->getOperand(2))->getAlignValue();`



https://github.com/llvm/llvm-project/pull/119822