Undef and poison

Author: krzysz00

llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp

@@ -1998,18 +1998,31 @@ PtrParts SplitPtrStructs::visitAddrSpaceCastInst(AddrSpaceCastInst &I) {
   Type *OffTy = ResTy->getElementType(1);
   Value *ZeroOff = Constant::getNullValue(OffTy);
 
-  // Special case for null pointers, which can be created by address space
-  // propagation.
+  // Special case for null pointers, undef, and poison, which can be created by
+  // address space propagation.
   auto *InConst = dyn_cast<Constant>(In);
   if (InConst && InConst->isNullValue()) {
     Value *NullRsrc = Constant::getNullValue(RsrcTy);
     SplitUsers.insert(&I);
     return {NullRsrc, ZeroOff};
   }
+  if (isa<PoisonValue>(In)) {
+    Value *PoisonRsrc = PoisonValue::get(RsrcTy);
+    Value *PoisonOff = PoisonValue::get(OffTy);
+    SplitUsers.insert(&I);
+    return {PoisonRsrc, PoisonOff};
+  }
+  if (isa<UndefValue>(In)) {
+    Value *UndefRsrc = UndefValue::get(RsrcTy);
+    Value *UndefOff = UndefValue::get(OffTy);
+    SplitUsers.insert(&I);
+    return {UndefRsrc, UndefOff};
+  }
 
   if (I.getSrcAddressSpace() != AMDGPUAS::BUFFER_RESOURCE)
-    report_fatal_error("Only buffer resources (addrspace 8) and null pointers "
-                       "can be cast to buffer fat pointers (addrspace 7)");
+    report_fatal_error(
+        "only buffer resources (addrspace 8) and null/poison pointers can be "
+        "cast to buffer fat pointers (addrspace 7)");
   SplitUsers.insert(&I);
   return {In, ZeroOff};
 }

llvm/test/CodeGen/AMDGPU/lower-buffer-fat-pointers-pointer-ops.ll

@@ -364,6 +364,42 @@ define i1 @test_null(ptr addrspace(7) %p) {
   ret i1 %is.null
 }
 
+define ptr addrspace(7) @addrspacecast_undef() {
+; CHECK-LABEL: define { ptr addrspace(8), i32 } @addrspacecast_undef
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { ptr addrspace(8), i32 } undef
+;
+  %ret = addrspacecast ptr undef to ptr addrspace(7)
+  ret ptr addrspace(7) %ret
+}
+
+define <2 x ptr addrspace(7)> @addrspacecast_undef_vec() {
+; CHECK-LABEL: define { <2 x ptr addrspace(8)>, <2 x i32> } @addrspacecast_undef_vec
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { <2 x ptr addrspace(8)>, <2 x i32> } undef
+;
+  %ret = addrspacecast <2 x ptr> undef to <2 x ptr addrspace(7)>
+  ret <2 x ptr addrspace(7)> %ret
+}
+
+define ptr addrspace(7) @addrspacecast_poison() {
+; CHECK-LABEL: define { ptr addrspace(8), i32 } @addrspacecast_poison
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { ptr addrspace(8), i32 } poison
+;
+  %ret = addrspacecast ptr poison to ptr addrspace(7)
+  ret ptr addrspace(7) %ret
+}
+
+define <2 x ptr addrspace(7)> @addrspacecast_poison_vec() {
+; CHECK-LABEL: define { <2 x ptr addrspace(8)>, <2 x i32> } @addrspacecast_poison_vec
+; CHECK-SAME: () #[[ATTR0]] {
+; CHECK-NEXT:    ret { <2 x ptr addrspace(8)>, <2 x i32> } poison
+;
+  %ret = addrspacecast <2 x ptr> poison to <2 x ptr addrspace(7)>
+  ret <2 x ptr addrspace(7)> %ret
+}
+
 declare ptr addrspace(7) @llvm.amdgcn.make.buffer.rsrc.p7.p1(ptr addrspace(1), i16, i32, i32)
 
 define ptr addrspace(7) @make_buffer_rsrc(ptr addrspace(1) %buf, i16 %stride, i32 %numRecords, i32 %flags) {