llvm dev - Nov 2015 - [PATCH] patch for missed constantFold optimization in InstCombine

Hi All,
llvm::ConstantFoldCompareInstOperands misses an optimization when it tries to
constantFold a compare instruction containing addrspacecast instead of
combination of ptrtoint and inttoptr. Adding the patched code snippet in the
code would enable the pass to handle addrspacecast and constantFold the missing
cases.
Attached is the .ll file for the reproducer. Let me know if there are any
suggestions/comments or I can commit the patch.

Patched code :
Index: ConstantFolding.cpp
==================================================================diff --git
a/llvm/trunk/lib/Analysis/ConstantFolding.cpp
b/llvm/trunk/lib/Analysis/ConstantFolding.cpp
--- a/llvm/trunk/lib/Analysis/ConstantFolding.cpp            (revision 252222)
+++ b/llvm/trunk/lib/Analysis/ConstantFolding.cpp        (working copy)
@@ -1137,6 +1137,12 @@
           return ConstantFoldCompareInstOperands(Predicate, C, Null, DL, TLI);
         }
       }
+
+      if (CE0->getOpcode() == Instruction::AddrSpaceCast) {
+          Constant *C = CE0->getOperand(0);
+          Constant *Null = Constant::getNullValue(C->getType());
+          return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI);
+      }
     }
     if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {


Thanks,
Tejas
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