Cleanup of the [SU]ADDO type legalization code. Patch by Duncan!

"It simplifies the type legalization part a bit, and produces better code by
teaching SelectionDAG about the extra bits in an i8 SADDO/UADDO node.  In
essence, I spontaneously decided that on x86 this i8 boolean result would be
either 0 or 1, and on other platforms 0/1 or 0/-1, depending on whether the
platform likes it's boolean zero extended or sign extended."

llvm-svn: 59864

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 02159de0c75..7d64b2441d9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1491,6 +1491,11 @@ void SelectionDAG::ComputeMaskedBits(SDValue Op, const APInt &Mask,
     KnownOne &= KnownOne2;
     KnownZero &= KnownZero2;
     return;
+  case ISD::SADDO:
+  case ISD::UADDO:
+    if (Op.getResNo() != 1)
+      return;
+    // The boolean result conforms to getSetCCResultContents.  Fall through.
   case ISD::SETCC:
     // If we know the result of a setcc has the top bits zero, use this info.
     if (TLI.getSetCCResultContents() == TargetLowering::ZeroOrOneSetCCResult &&
@@ -1893,7 +1898,12 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const{
     if (Tmp == 1) return 1;  // Early out.
     Tmp2 = ComputeNumSignBits(Op.getOperand(2), Depth+1);
     return std::min(Tmp, Tmp2);
-    
+
+  case ISD::SADDO:
+  case ISD::UADDO:
+    if (Op.getResNo() != 1)
+      break;
+    // The boolean result conforms to getSetCCResultContents.  Fall through.
   case ISD::SETCC:
     // If setcc returns 0/-1, all bits are sign bits.
     if (TLI.getSetCCResultContents() ==