[PATCH] D33801: [InstSimplify][ConstantFolding] Teach constant folding how to handle icmp null, (inttoptr x) as well as it handles icmp (inttoptr x), null

[Craig Topper via Phabricator via llvm-commits]

craig.topper updated this revision to Diff 101124.
craig.topper added a comment.

Implement with no code duplication. Just detect that LHS is not a constant expr, but RHS is. If that's the case swap the predicate and the operands and recurse back into the same function.


https://reviews.llvm.org/D33801

Files:
  lib/Analysis/ConstantFolding.cpp
  test/Transforms/InstSimplify/compare.ll


Index: test/Transforms/InstSimplify/compare.ll
===================================================================
--- test/Transforms/InstSimplify/compare.ll
+++ test/Transforms/InstSimplify/compare.ll
@@ -1289,7 +1289,7 @@
 
 define i1 @constant_fold_null_inttoptr() {
 ; CHECK-LABEL: @constant_fold_null_inttoptr(
-; CHECK-NEXT:    ret i1 icmp eq (i32* inttoptr (i64 32 to i32*), i32* null)
+; CHECK-NEXT:    ret i1 false
 ;
   %x = icmp eq i32* null, inttoptr (i64 32 to i32*)
   ret i1 %x
Index: lib/Analysis/ConstantFolding.cpp
===================================================================
--- lib/Analysis/ConstantFolding.cpp
+++ lib/Analysis/ConstantFolding.cpp
@@ -1170,7 +1170,9 @@
                                                 const DataLayout &DL,
                                                 const TargetLibraryInfo *TLI) {
   // fold: icmp (inttoptr x), null         -> icmp x, 0
+  // fold: icmp null, (inttoptr x)         -> icmp 0, x
   // fold: icmp (ptrtoint x), 0            -> icmp x, null
+  // fold: icmp 0, (ptrtoint x)            -> icmp null, x
   // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
   // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
   //
@@ -1240,6 +1242,11 @@
         Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
       return ConstantFoldBinaryOpOperands(OpC, LHS, RHS, DL);
     }
+  } else if (isa<ConstantExpr>(Ops1)) {
+    // If RHS is a constant expression, but the left side isn't, swap the
+    // operands and try again.
+    Predicate = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)Predicate);
+    return ConstantFoldCompareInstOperands(Predicate, Ops1, Ops0, DL, TLI);
   }
 
   return ConstantExpr::getCompare(Predicate, Ops0, Ops1);


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