[llvm] fd1094f - [ConstantFolding] Clean up Intrinsics::abs undef handling

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2022-01-10T17:04:03Z
New Revision: fd1094f318971e4aaa1c6b836ba93e757c8b913a

URL: https://github.com/llvm/llvm-project/commit/fd1094f318971e4aaa1c6b836ba93e757c8b913a
DIFF: https://github.com/llvm/llvm-project/commit/fd1094f318971e4aaa1c6b836ba93e757c8b913a.diff

LOG: [ConstantFolding] Clean up Intrinsics::abs undef handling

Match cttz/ctlz handling by assuming C1 == 0 if C1 != 1 - I've added an assertion as well.

Fixes static analyzer nullptr dereference warnings.

Added: 
    

Modified: 
    llvm/lib/Analysis/ConstantFolding.cpp

Removed: 
    


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diff  --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index d25694b0c0eda..103992de3dc08 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -2572,13 +2572,15 @@ static Constant *ConstantFoldScalarCall2(StringRef Name,
         return ConstantInt::get(Ty, C0->countLeadingZeros());
 
     case Intrinsic::abs:
-      // Undef or minimum val operand with poison min --> undef
       assert(C1 && "Must be constant int");
+      assert((C1->isOne() || C1->isZero()) && "Must be 0 or 1");
+
+      // Undef or minimum val operand with poison min --> undef
       if (C1->isOne() && (!C0 || C0->isMinSignedValue()))
         return UndefValue::get(Ty);
 
       // Undef operand with no poison min --> 0 (sign bit must be clear)
-      if (C1->isZero() && !C0)
+      if (!C0)
         return Constant::getNullValue(Ty);
 
       return ConstantInt::get(Ty, C0->abs());