[llvm] r304559 - [InstSimplify][ConstantFolding] Teach constant folding how to handle icmp null, (inttoptr x) as well as it handles icmp (inttoptr x), null

[Craig Topper via llvm-commits]

Author: ctopper
Date: Fri Jun  2 11:17:32 2017
New Revision: 304559

URL: http://llvm.org/viewvc/llvm-project?rev=304559&view=rev
Log:
[InstSimplify][ConstantFolding] Teach constant folding how to handle icmp null, (inttoptr x) as well as it handles icmp (inttoptr x), null

Summary:
The constant folding code currently assumes that the constant expression will always be on the left and the simple null will be on the right. But that's not true at least on the path from InstSimplify.

This patch adds support to ConstantFolding to detect the reversed case.

Reviewers: spatel, dberlin, majnemer, davide, joey

Reviewed By: joey

Subscribers: joey, llvm-commits

Differential Revision: https://reviews.llvm.org/D33801

Modified:
    llvm/trunk/lib/Analysis/ConstantFolding.cpp
    llvm/trunk/test/Transforms/InstSimplify/compare.ll

Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=304559&r1=304558&r2=304559&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Fri Jun  2 11:17:32 2017
@@ -1170,7 +1170,9 @@ Constant *llvm::ConstantFoldCompareInstO
                                                 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 @@ Constant *llvm::ConstantFoldCompareInstO
         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);

Modified: llvm/trunk/test/Transforms/InstSimplify/compare.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/compare.ll?rev=304559&r1=304558&r2=304559&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/compare.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/compare.ll Fri Jun  2 11:17:32 2017
@@ -1289,7 +1289,7 @@ define i1 @constant_fold_inttoptr_null()
 
 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