[Constant] Make Constant::getSplatValue return poison on poison (#141870)

This is a follow up from #141845. 

TargetTransformInfo::getOperandInfo needs to be updated to check for
undef values as otherwise a splat is considered a constant, and some
RISC-V cost model tests will start adding a cost to materialize the
constant.

1 files changed, 0 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 40302fb..2476dc5 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -3794,11 +3794,6 @@ static Constant *ConstantFoldScalableVectorCall(
       SplatOps.push_back(Op);
       continue;
     }
-    // TODO: Should getSplatValue return a poison scalar for a poison vector?
-    if (isa<PoisonValue>(Op)) {
-      SplatOps.push_back(PoisonValue::get(Op->getType()->getScalarType()));
-      continue;
-    }
     Constant *Splat = Op->getSplatValue();
     if (!Splat)
       return nullptr;