[llvm] [AMDGPU][MC] Allow UC_VERSION_* constant reuse (PR #96461)

[Jay Foad via llvm-commits]

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@@ -2366,8 +2366,12 @@ const MCExpr *AMDGPUDisassembler::createConstantSymbolExpr(StringRef Id,
                                                            int64_t Val) {
   MCContext &Ctx = getContext();
   MCSymbol *Sym = Ctx.getOrCreateSymbol(Id);
-  assert(!Sym->isVariable());
-  Sym->setVariableValue(MCConstantExpr::create(Val, Ctx));
+  int64_t Res = ~Val;
+  assert(!Sym->isVariable() ||
+         (Sym->getVariableValue()->evaluateAsAbsolute(Res) && Res == Val));
+  (void)Res;
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jayfoad wrote:

This makes me question whether implementing `UC_VERSION_*` as symbols _that the user can redefine_ was the best choice in the first place. But I don't have any alternative suggestion.

https://github.com/llvm/llvm-project/pull/96461