Lower null-cast patterns

Match `addrspacecast (Ty1 null to Ty2)` pattern to `null`

Author: igorban-intel

IGC/VectorCompiler/lib/GenXCodeGen/GenXPatternMatch.cpp

@@ -4168,6 +4168,17 @@ bool GenXPatternMatch::placeConstants(Function *F) {
           continue;
         if (opMustBeConstant(Inst, i))
           continue;
+
+        // Match `addrspacecast (Ty1 null to Ty2)` pattern to `null`
+        if (auto *Const = dyn_cast<ConstantExpr>(C); Const && Const->isCast()) {
+          auto *NullVal = dyn_cast<Constant>(Const->getOperand(0));
+          if (NullVal && NullVal->isNullValue()) {
+            auto *Ty = cast<PointerType>(Const->getType());
+            auto *NewConst = llvm::ConstantPointerNull::get(Ty);
+            Inst->setOperand(i, NewConst);
+            Changed = true;
+          }
+        }
         auto Ty = C->getType();
         if (!Ty->isVectorTy() || C->getSplatValue())
           continue;

IGC/VectorCompiler/test/PatternMatch/icmp-patt.ll

@@ -88,4 +88,12 @@ case4:
 
 declare <16 x i32> @llvm.genx.wrregionf.v16i32.v1i32.i16.i1(<16 x i32>, <1 x i32>, i32, i32, i32, i16, i32, i1)
 declare <16 x i32> @llvm.genx.wrregionf.v16i32.v2i32.i16.v2i1(<16 x i32>, <2 x i32>, i32, i32, i32, i16, i32, <2 x i1>)
-declare <16 x i32> @llvm.genx.wrregionf.v16i32.v1i32.i16.v16i1(<16 x i32>, <1 x i32>, i32, i32, i32, i16, i32, <16 x i1>)
+declare <16 x i32> @llvm.genx.wrregionf.v16i32.v1i32.i16.v16i1(<16 x i32>, <1 x i32>, i32, i32, i32, i16, i32, <16 x i1>)
+
+; CHECK-LABEL: test_addrspacecast
+define i1 @test_addrspacecast(i64 %in) {
+; CHECK: %res = icmp ne [17 x i8] addrspace(1)* %b,  null
+  %b = inttoptr i64 %in to [17 x i8] addrspace(1)*
+  %res = icmp ne [17 x i8] addrspace(1)* %b, addrspacecast ([17 x i8] addrspace(4)* null to [17 x i8] addrspace(1)*)
+  ret i1 %res
+}