[llvm] [WIP][AMDGPU][Attributor] Make `AAAMDFlatWorkGroupSize` honor existing attribute (PR #114357)

[Shilei Tian via llvm-commits]

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@@ -728,12 +735,43 @@ struct AAAMDSizeRangeAttribute
     };
 
     bool AllCallSitesKnown = true;
-    if (!A.checkForAllCallSites(CheckCallSite, *this, true, AllCallSitesKnown))
+    if (!A.checkForAllCallSites(CheckCallSite, *this,
+                                /*RequireAllCallSites=*/true,
+                                AllCallSitesKnown))
       return indicatePessimisticFixpoint();
 
     return Change;
   }
 
+  /// Clamp the assumed range to the default value ([Min, Max]) and emit the
+  /// attribute if it is not same as default.
+  ChangeStatus
+  emitAttributeIfNotDefaultAfterClamp(Attributor &A,
+                                      std::pair<unsigned, unsigned> Default) {
+    auto [Min, Max] = Default;
+    unsigned Lower = getAssumed().getLower().getZExtValue();
+    unsigned Upper = getAssumed().getUpper().getZExtValue();
+
+    // Clamp the range to the default value.
+    if (Lower < Min)
+      Lower = Min;
+    if (Upper > Max + 1)
+      Upper = Max + 1;
+
+    // No manifest if the value is same as default after clamp.
+    if (Lower == Min && Upper == Max + 1)
+      return ChangeStatus::UNCHANGED;
+
+    Function *F = getAssociatedFunction();
+    LLVMContext &Ctx = F->getContext();
+    SmallString<10> Buffer;
+    raw_svector_ostream OS(Buffer);
+    OS << Lower << ',' << Upper - 1;
+    return A.manifestAttrs(getIRPosition(),
+                           {Attribute::get(Ctx, AttrName, OS.str())},
+                           /* ForceReplace=*/true);
+  }
+
   ChangeStatus emitAttributeIfNotDefault(Attributor &A, unsigned Min,
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shiltian wrote:

This will be eventually removed.

https://github.com/llvm/llvm-project/pull/114357