[InstSimplify][ConstantFolding] Teach constant folding how to handle icmp 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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304559 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 6a1af87450c90837ca9038d7bac5588495600788..a906770dbb341ba466a58d72949cd0f29e304d22 100644 (file)
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -1170,7 +1170,9 @@ Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
                                                 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::ConstantFoldCompareInstOperands(unsigned Predicate,
         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);

diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index 9125367a7bf9a3137eeb79a4e75bdf8e6b8e0b1d..20ebd36991a57a33c913098c427310a44eac58a2 100644 (file)
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/test/Transforms/InstSimplify/compare.ll
@@ -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