[llvm] [AMDGPU] Handle lowering addrspace casts from LDS to FLAT address in amdgpu-sw-lower-lds. (PR #121214)

[via llvm-commits]

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@@ -655,20 +654,40 @@ void AMDGPUSwLowerLDS::getLDSMemoryInstructions(
       } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(&Inst)) {
         if (XCHG->getPointerAddressSpace() == AMDGPUAS::LOCAL_ADDRESS)
           LDSInstructions.insert(&Inst);
+      } else if (AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(&Inst)) {
+        if (ASC->getSrcAddressSpace() == AMDGPUAS::LOCAL_ADDRESS &&
+            ASC->getDestAddressSpace() == AMDGPUAS::FLAT_ADDRESS)
+          LDSInstructions.insert(&Inst);
       } else
         continue;
     }
   }
 }
 
-Value *
-AMDGPUSwLowerLDS::getTranslatedGlobalMemoryGEPOfLDSPointer(Value *LoadMallocPtr,
+Value *AMDGPUSwLowerLDS::getTranslatedGlobalMemoryPtrOfLDS(Value *LoadMallocPtr,
                                                            Value *LDSPtr) {
   assert(LDSPtr && "Invalid LDS pointer operand");
+  Type *LDSPtrType = LDSPtr->getType();
+
+  if (LDSPtrType->isVectorTy()) {
+    // Handle vector of pointers
+    VectorType *VecPtrTy = cast<VectorType>(LDSPtrType);
+    ElementCount NumElements = VecPtrTy->getElementCount();
+    Type *Int32VecTy = VectorType::get(IRB.getInt32Ty(), NumElements);
+    Value *PtrToInt = IRB.CreatePtrToInt(LDSPtr, Int32VecTy);
+    Type *GlobalPtrVecTy =
+        VectorType::get(IRB.getPtrTy(AMDGPUAS::GLOBAL_ADDRESS), NumElements);
+    Value *GlobalPtrVec = PoisonValue::get(GlobalPtrVecTy);
+    for (uint64_t Index = 0; Index < NumElements.getKnownMinValue(); ++Index) {
+      Value *ExtElem = IRB.CreateExtractElement(PtrToInt, Index);
+      Value *Gep =
+          IRB.CreateInBoundsGEP(IRB.getInt8Ty(), LoadMallocPtr, {ExtElem});
+      GlobalPtrVec = IRB.CreateInsertElement(GlobalPtrVec, Gep, Index);
+    }
+    return GlobalPtrVec;
+  }
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skc7 wrote:

Thanks for feedback @arsenm . I was unaware that GEP supports vector of ptrs [[LINK](https://llvm.org/docs/LangRef.html#vector-of-pointers)] . Have updated PR to instead use vector of ptrs. 

https://github.com/llvm/llvm-project/pull/121214