Make use of APInt::countLeadingOnes. NFC.

jayfoad · jayfoad · commit 7cdbf1ed4b94 · 2020-03-23T09:08:20.000Z
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4048,13 +4048,10 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
     return FirstAnswer;
   }
 
-  // Okay, we know that the sign bit in Mask is set.  Use CLZ to determine
+  // Okay, we know that the sign bit in Mask is set.  Use CLO to determine
   // the number of identical bits in the top of the input value.
-  Mask = ~Mask;
   Mask <<= Mask.getBitWidth()-VTBits;
-  // Return # leading zeros.  We use 'min' here in case Val was zero before
-  // shifting.  We don't want to return '64' as for an i32 "0".
-  return std::max(FirstAnswer, std::min(VTBits, Mask.countLeadingZeros()));
+  return std::max(FirstAnswer, Mask.countLeadingOnes());
 }
 
 bool SelectionDAG::isBaseWithConstantOffset(SDValue Op) const {

Original file line number	Diff line number	Diff line change
`@@ -4048,13 +4048,10 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,`
`4048`	`4048`	`return FirstAnswer;`
`4049`	`4049`	`}`
`4050`	`4050`
`4051`		`- // Okay, we know that the sign bit in Mask is set. Use CLZ to determine`
	`4051`	`+ // Okay, we know that the sign bit in Mask is set. Use CLO to determine`
`4052`	`4052`	`// the number of identical bits in the top of the input value.`
`4053`		`- Mask = ~Mask;`
`4054`	`4053`	`Mask <<= Mask.getBitWidth()-VTBits;`
`4055`		`- // Return # leading zeros. We use 'min' here in case Val was zero before`
`4056`		`- // shifting. We don't want to return '64' as for an i32 "0".`
`4057`		`- return std::max(FirstAnswer, std::min(VTBits, Mask.countLeadingZeros()));`
	`4054`	`+ return std::max(FirstAnswer, Mask.countLeadingOnes());`
`4058`	`4055`	`}`
`4059`	`4056`
`4060`	`4057`	`bool SelectionDAG::isBaseWithConstantOffset(SDValue Op) const {`