[llvm] MCExpr-ify SIProgramInfo (PR #88257)

[Pierre van Houtryve via llvm-commits]

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@@ -86,6 +105,158 @@ bool AMDGPUVariadicMCExpr::evaluateAsRelocatableImpl(
     MCValue &Res, const MCAsmLayout *Layout, const MCFixup *Fixup) const {
   std::optional<int64_t> Total;
 
+  auto TryGetMCExprValue = [&](const MCExpr *Arg, uint64_t &ConstantValue) {
+    MCValue MCVal;
+    if (!Arg->evaluateAsRelocatable(MCVal, Layout, Fixup) ||
+        !MCVal.isAbsolute())
+      return false;
+
+    ConstantValue = MCVal.getConstant();
+    return true;
+  };
+
+  if (Kind == AGVK_ExtraSGPRs) {
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Pierre-vh wrote:

I think at this point it might be better to create separate functions (static helpers?) for each of these cases and call them in a switch. 
It'll make it more readable. 

https://github.com/llvm/llvm-project/pull/88257