[llvm] 9d0bfce - [SelectionDAG] ComputeNumSignBits - use Valid Min/Max shift amount helpers directly. NFCI.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2020-05-30T14:02:14+01:00
New Revision: 9d0bfcec8377acc29e8a9983e8343dba8e7e900d

URL: https://github.com/llvm/llvm-project/commit/9d0bfcec8377acc29e8a9983e8343dba8e7e900d
DIFF: https://github.com/llvm/llvm-project/commit/9d0bfcec8377acc29e8a9983e8343dba8e7e900d.diff

LOG: [SelectionDAG] ComputeNumSignBits - use Valid Min/Max shift amount helpers directly. NFCI.

We are calling getValidShiftAmountConstant first followed by getValidMinimumShiftAmountConstant/getValidMaximumShiftAmountConstant if that failed. But both are used in the same way in ComputeNumSignBits and the Min/Max variants call getValidShiftAmountConstant internally anyhow.

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3cba91a11d42..232b1ea6bb78 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3657,23 +3657,17 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
   case ISD::SRA:
     Tmp = ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1);
     // SRA X, C -> adds C sign bits.
-    if (const APInt *ShAmt = getValidShiftAmountConstant(Op, DemandedElts))
-      Tmp = std::min<uint64_t>(Tmp + ShAmt->getZExtValue(), VTBits);
-    else if (const APInt *ShAmt =
-                 getValidMinimumShiftAmountConstant(Op, DemandedElts))
+    if (const APInt *ShAmt =
+            getValidMinimumShiftAmountConstant(Op, DemandedElts))
       Tmp = std::min<uint64_t>(Tmp + ShAmt->getZExtValue(), VTBits);
     return Tmp;
   case ISD::SHL:
-    if (const APInt *ShAmt = getValidShiftAmountConstant(Op, DemandedElts)) {
+    if (const APInt *ShAmt =
+            getValidMaximumShiftAmountConstant(Op, DemandedElts)) {
       // shl destroys sign bits, ensure it doesn't shift out all sign bits.
       Tmp = ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1);
       if (ShAmt->ult(Tmp))
         return Tmp - ShAmt->getZExtValue();
-    } else if (const APInt *ShAmt =
-                   getValidMaximumShiftAmountConstant(Op, DemandedElts)) {
-      Tmp = ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1);
-      if (ShAmt->ult(Tmp))
-        return Tmp - ShAmt->getZExtValue();
     }
     break;
   case ISD::AND: