When forming SSE min and max nodes for UGE and ULE comparisons, it's

necessary to swap the operands to handle NaN and negative zero properly.

Also, reintroduce logic for checking for NaN conditions when forming
SSE min and max instructions, fixed to take into consideration NaNs and
negative zeros. This allows forming min and max instructions in more
cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97025 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f8930b8ff0..41050211b2 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2235,6 +2235,29 @@ bool SelectionDAG::isKnownNeverNaN(SDValue Op) const {
   return false;
 }
 
+bool SelectionDAG::isKnownNeverZero(SDValue Op) const {
+  // If the value is a constant, we can obviously see if it is a zero or not.
+  if (const ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Op))
+    return !C->isZero();
+
+  // TODO: Recognize more cases here.
+
+  return false;
+}
+
+bool SelectionDAG::isEqualTo(SDValue A, SDValue B) const {
+  // Check the obvious case.
+  if (A == B) return true;
+
+  // For for negative and positive zero.
+  if (const ConstantFPSDNode *CA = dyn_cast<ConstantFPSDNode>(A))
+    if (const ConstantFPSDNode *CB = dyn_cast<ConstantFPSDNode>(B))
+      if (CA->isZero() && CB->isZero()) return true;
+
+  // Otherwise they may not be equal.
+  return false;
+}
+
 bool SelectionDAG::isVerifiedDebugInfoDesc(SDValue Op) const {
   GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(Op);
   if (!GA) return false;