revert r328921 - [DAGCombine] (float)((int) f) --> ftrunc (PR36617)

This change is exposing UB in source code - as was warned/predicted. :)
See D44909 for discussion. Reverting while we figure out how to fix things.

llvm-svn: 329920

1 files changed, 0 insertions, 18 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index dc87e899455..42c754a5331 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10890,15 +10890,6 @@ SDValue DAGCombiner::visitSINT_TO_FP(SDNode *N) {
     }
   }
 
-  // fptosi rounds towards zero, so converting from FP to integer and back is
-  // the same as an 'ftrunc': sitofp (fptosi X) --> ftrunc X
-  // We only do this if the target has legal ftrunc, otherwise we'd likely be
-  // replacing casts with a libcall.
-  if (N0.getOpcode() == ISD::FP_TO_SINT &&
-      N0.getOperand(0).getValueType() == VT &&
-      TLI.isOperationLegal(ISD::FTRUNC, VT))
-    return DAG.getNode(ISD::FTRUNC, SDLoc(N), VT, N0.getOperand(0));
-
   return SDValue();
 }
 
@@ -10938,15 +10929,6 @@ SDValue DAGCombiner::visitUINT_TO_FP(SDNode *N) {
     }
   }
 
-  // fptoui rounds towards zero, so converting from FP to integer and back is
-  // the same as an 'ftrunc': uitofp (fptoui X) --> ftrunc X
-  // We only do this if the target has legal ftrunc, otherwise we'd likely be
-  // replacing casts with a libcall.
-  if (N0.getOpcode() == ISD::FP_TO_UINT &&
-      N0.getOperand(0).getValueType() == VT &&
-      TLI.isOperationLegal(ISD::FTRUNC, VT))
-    return DAG.getNode(ISD::FTRUNC, SDLoc(N), VT, N0.getOperand(0));
-
   return SDValue();
 }