[llvm] r349400 - [X86][SSE] Split SimplifyDemandedBitsForTargetNode X86ISD::VSRLI/VSRAI handling.

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Mon Dec 17 13:36:17 2018
New Revision: 349400

URL: http://llvm.org/viewvc/llvm-project?rev=349400&view=rev
Log:
[X86][SSE] Split SimplifyDemandedBitsForTargetNode X86ISD::VSRLI/VSRAI handling.

First step towards adding more capable combines to fix comments in D55768.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=349400&r1=349399&r2=349400&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Mon Dec 17 13:36:17 2018
@@ -32410,7 +32410,6 @@ bool X86TargetLowering::SimplifyDemanded
     }
     break;
   }
-  case X86ISD::VSRAI:
   case X86ISD::VSRLI: {
     if (auto *ShiftImm = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
       if (ShiftImm->getAPIntValue().uge(BitWidth))
@@ -32420,10 +32419,24 @@ bool X86TargetLowering::SimplifyDemanded
       unsigned ShAmt = ShiftImm->getZExtValue();
       APInt DemandedMask = OriginalDemandedBits << ShAmt;
 
+      if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask,
+                               OriginalDemandedElts, KnownOp, TLO, Depth + 1))
+        return true;
+    }
+    break;
+  }
+  case X86ISD::VSRAI: {
+    if (auto *ShiftImm = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
+      if (ShiftImm->getAPIntValue().uge(BitWidth))
+        break;
+
+      KnownBits KnownOp;
+      unsigned ShAmt = ShiftImm->getZExtValue();
+      APInt DemandedMask = OriginalDemandedBits << ShAmt;
+
       // If any of the demanded bits are produced by the sign extension, we also
       // demand the input sign bit.
-      if (Opc == X86ISD::VSRAI &&
-          OriginalDemandedBits.countLeadingZeros() < ShAmt)
+      if (OriginalDemandedBits.countLeadingZeros() < ShAmt)
         DemandedMask.setSignBit();
 
       if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask,