Add test case and adjust tests.

Author: ekpyron

test/cmdlineTests/viair_subobject_optimization/args

@@ -0,0 +1 @@
+--experimental-via-ir --optimize --asm

test/cmdlineTests/viair_subobject_optimization/input.sol

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+// SPDX-License-Identifier: GPL-3.0
+pragma solidity >0.0.0;
+
+contract C {
+  constructor(uint x) {
+    // In earlier versions of the compiler, the resulting assembly pushed the constant
+    // 0xFFFFFFFFFFFFFFFF42 directly in the subassembly of D, while it was optimized to
+    // ``sub(shl(0x48, 0x01), 0xbe)`` when C was compiled in isolation.
+    // Now the assembly is expected to contain two instances of ``sub(shl(0x48, 0x01), 0xbe)``,
+    // one in the creation code of ``C`` directly, one in a subassembly of ``D``.
+    // The constant 0xFFFFFFFFFFFFFFFF42 should not occur in the assembly output at all.
+    if (x == 0xFFFFFFFFFFFFFFFF42)
+      revert();
+  }
+}
+contract D {
+  function f() public pure returns (bytes memory) {
+    return type(C).creationCode;
+  }
+}