[llvm] e414ba3 - [ValueTracking] Shufflevector produces poison rather than undef

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-12-21T15:21:23+01:00
New Revision: e414ba33b44971d47d24d75b7da94898d2cc8bde

URL: https://github.com/llvm/llvm-project/commit/e414ba33b44971d47d24d75b7da94898d2cc8bde
DIFF: https://github.com/llvm/llvm-project/commit/e414ba33b44971d47d24d75b7da94898d2cc8bde.diff

LOG: [ValueTracking] Shufflevector produces poison rather than undef

Shufflevector semantics have changed so that poison mask elements
return poison rather than undef. Reflect this in the
canCreateUndefOrPoison() implementation.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/unittests/Analysis/ValueTrackingTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index efdb3fc2858249..2ce660b9a858eb 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6674,9 +6674,6 @@ static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly,
     return false;
   }
   case Instruction::ShuffleVector: {
-    // shufflevector may return undef.
-    if (PoisonOnly)
-      return false;
     ArrayRef<int> Mask = isa<ConstantExpr>(Op)
                              ? cast<ConstantExpr>(Op)->getShuffleMask()
                              : cast<ShuffleVectorInst>(Op)->getShuffleMask();

diff  --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index 0d3a594da0c067..27f631884072b5 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -1177,12 +1177,12 @@ TEST(ValueTracking, canCreatePoisonOrUndef) {
       {{false, false},
        "shufflevector <4 x i32> %vx, <4 x i32> %vx2, "
        "<4 x i32> <i32 0, i32 1, i32 2, i32 3>"},
-      {{false, true},
+      {{true, false},
        "shufflevector <4 x i32> %vx, <4 x i32> %vx2, "
-       "<4 x i32> <i32 0, i32 1, i32 2, i32 undef>"},
-      {{false, true},
+       "<4 x i32> <i32 0, i32 1, i32 2, i32 poison>"},
+      {{true, false},
        "shufflevector <vscale x 4 x i32> %svx, "
-       "<vscale x 4 x i32> %svx, <vscale x 4 x i32> undef"},
+       "<vscale x 4 x i32> %svx, <vscale x 4 x i32> poison"},
       {{true, false}, "call i32 @g(i32 %x)"},
       {{false, false}, "call noundef i32 @g(i32 %x)"},
       {{true, false}, "fcmp nnan oeq float %fx, %fy"},