[llvm] [MergeFunc] Preserve observable function pointer identity (PR #213604)

[Nikita Popov via llvm-commits]

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@@ -964,11 +969,17 @@ int FunctionComparator::cmpBasicBlocks(const BasicBlock *BBL,
       return Res;
     if (needToCmpOperands) {
       assert(InstL->getNumOperands() == InstR->getNumOperands());
+      const auto *CBL = dyn_cast<CallBase>(InstL);
+      const auto *CBR = dyn_cast<CallBase>(InstR);
 
       for (unsigned i = 0, e = InstL->getNumOperands(); i != e; ++i) {
         Value *OpL = InstL->getOperand(i);
         Value *OpR = InstR->getOperand(i);
-        if (int Res = cmpValues(OpL, OpR))
+        ValueComparisonKind Kind = ValueComparisonKind::Normal;
+        if (CBL && CBR && CBL->isCallee(&InstL->getOperandUse(i)) &&
+            CBR->isCallee(&InstR->getOperandUse(i)))
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nikic wrote:

The second isCallee() check can be an assert.

https://github.com/llvm/llvm-project/pull/213604