[EraVM][ELF] Handle emission of NULL pointer explicitly

Make EraVMAsmPrinter handle ConstantPointerNull value by explicitly
emitting an equivalent of `.cell 0`, otherwise the generic code would
try to emit 256-bit wide zero integer triggering an assertion

    Assertion `1 <= Size && Size <= 8 && "Invalid size"' failed.

in `MCStreamer::emitIntValue(uint64_t, unsigned int)`.

llvm/lib/Target/EraVM/EraVMAsmPrinter.cpp

@@ -294,6 +294,11 @@ void EraVMAsmPrinter::emitGlobalConstant(const DataLayout &DL,
     return;
   }
 
+  if (isa<ConstantPointerNull>(CV)) {
+    Streamer->emitCell(APInt::getZero(256));
+    return;
+  }
+
   AsmPrinter::emitGlobalConstant(DL, CV);
 }
 

llvm/test/MC/EraVM/encoding/data.ll

@@ -0,0 +1,66 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -filetype=obj -o %t.o < %s
+; RUN: llvm-readelf --syms --hex-dump=.data %t.o | FileCheck --check-prefix=DATA %s
+
+target datalayout = "E-p:256:256-i8:256:256:256-i256:256:256-S32-a:256:256"
+target triple = "eravm"
+
+; Test zero and non-zero initializers
+@var1 = global i256 0, align 32
+@var2 = global i256 42, align 32
+@ptr = global ptr addrspace(3) null, align 32
+
+define void @set(ptr addrspace(3) %p, i256 %v1, i256 %v2) nounwind {
+  store ptr addrspace(3) %p, ptr @ptr, align 32
+  store i256 %v1, ptr @var1, align 32
+  store i256 %v2, ptr @var2, align 32
+  ret void
+}
+; CHECK-LABEL: set:
+; CHECK:         add     r2, r0, stack[@var1]
+; CHECK-NEXT:    ptr.add r1, r0, stack[@ptr]
+; CHECK-NEXT:    add     r3, r0, stack[@var2]
+; CHECK-NEXT:    ret
+
+
+define ptr addrspace(3) @get() nounwind {
+  %p = load ptr addrspace(3), ptr @ptr, align 32
+  %v1 = load i256, ptr @var1, align 32
+  %v2 = load i256, ptr @var2, align 32
+  %index = mul i256 %v1, %v2
+  %res = getelementptr i8, ptr addrspace(3) %p, i256 %index
+  ret ptr addrspace(3) %res
+}
+; CHECK-LABEL: get:
+; CHECK:         add     stack[@var2], r0, r1
+; CHECK-NEXT:    mul     stack[@var1], r1, r1, r2
+; CHECK-NEXT:    ptr.add stack[@ptr], r1, r1
+; CHECK-NEXT:    ret
+
+; CHECK:       .data
+; CHECK:       .globl var1
+; CHECK-NEXT:  .p2align 5, 0x0
+; CHECK-NEXT:var1:
+; CHECK-NEXT:  .cell 0
+; CHECK:       .globl var2
+; CHECK-NEXT:  .p2align 5, 0x0
+; CHECK-NEXT:var2:
+; CHECK-NEXT:  .cell 42
+; CHECK:       .globl ptr
+; CHECK-NEXT:  .p2align 5, 0x0
+; CHECK-NEXT:ptr:
+; CHECK-NEXT:  .cell 0
+
+; Check symbol values only, ignore "Num" column as well as unrelated symbols.
+; DATA: Symbol table '.symtab' {{.*}}
+; DATA: 00000000     0 NOTYPE  GLOBAL DEFAULT     4 var1
+; DATA: 00000040     0 NOTYPE  GLOBAL DEFAULT     4 ptr
+; DATA: 00000020     0 NOTYPE  GLOBAL DEFAULT     4 var2
+
+; DATA:      Hex dump of section '.data':
+; DATA-NEXT: 0x00000000 00000000 00000000 00000000 00000000 ................
+; DATA-NEXT: 0x00000010 00000000 00000000 00000000 00000000 ................
+; DATA-NEXT: 0x00000020 00000000 00000000 00000000 00000000 ................
+; DATA-NEXT: 0x00000030 00000000 00000000 00000000 0000002a ...............*
+; DATA-NEXT: 0x00000040 00000000 00000000 00000000 00000000 ................
+; DATA-NEXT: 0x00000050 00000000 00000000 00000000 00000000 ................