Case handling MachineOperandType address of a global value in SIFoldOperands

While `FoldingImmLike` accepts `MO_Immediate`, `MO_FrameIndex` and `MO_GlobalAddress`, the conditional block after it only covers the first 2, so I have added a case for the global value as well.

Author: malavikasamak

clang/include/clang/Basic/AttrDocs.td

@@ -7517,9 +7517,11 @@ the field it is attached to, and it may also lead to emission of automatic fix-i
 hints which would help the user replace the use of unsafe functions(/fields) with safe
 alternatives, though the attribute can be used even when the fix can't be automated.
 
-* Attribute attached to functions: The attribute does not suppress
-  ``-Wunsafe-buffer-usage`` inside the function to which it is attached.
-  These warnings still need to be addressed.
+* Attribute attached to functions: The attribute suppresses all
+  ``-Wunsafe-buffer-usage`` warnings within the function it is attached to, as the
+  function is now classified as unsafe. The attribute should be used carefully, as it
+  will silence all unsafe operation warnings inside the function; including any new
+  unsafe operations introduced in the future.
 
   The attribute is warranted even if the only way a function can overflow
   the buffer is by violating the function's preconditions. For example, it

llvm/lib/Target/AMDGPU/SIFoldOperands.cpp

@@ -1161,8 +1161,10 @@ void SIFoldOperandsImpl::foldOperand(
 
         if (OpToFold.isImm())
           UseMI->getOperand(1).ChangeToImmediate(OpToFold.getImm());
-        else
+        else if(OpToFold.isFI())
           UseMI->getOperand(1).ChangeToFrameIndex(OpToFold.getIndex());
+        else if(OpToFold.isGlobal())
+          return;
         UseMI->removeOperand(2); // Remove exec read (or src1 for readlane)
         return;
       }