[llvm] [AMDGPU] Let LowerModuleLDS run twice on the same module (PR #81729)

[Jon Chesterfield via llvm-commits]

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@@ -345,10 +347,18 @@ class AMDGPULowerModuleLDS {
         continue;
       }
 
-      if (GV.isAbsoluteSymbolRef()) {
-        report_fatal_error(
-            "LDS variables with absolute addresses are unimplemented.");
-      }
+      // Check if the module is consistent: either all GVs are absolute (happens
+      // when we run the pass more than once), or none are.
+      if (HasAbsoluteGVs.has_value()) {
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JonChesterfield wrote:

Lets call GV.isAbsoluteSymbolRef once instead of three times

https://github.com/llvm/llvm-project/pull/81729