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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Carl Ritson (perlfu)

<details>
<summary>Changes</summary>

If more than one disassembler is created for a context then allow reuse of existing constants.
Update assertion to validate constant contents.

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


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp (+6-2) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index 76a559c9443bd..d61e8ebb866df 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -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;
+  if (!Sym->isVariable())
+    Sym->setVariableValue(MCConstantExpr::create(Val, Ctx));
   return MCSymbolRefExpr::create(Sym, Ctx);
 }
 

``````````

</details>


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