Update ARMISelLowering.cpp

Author: AZero13

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -20178,7 +20178,7 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
   if (DemandedBits.popcount() == 32)
     return false;
 
-    // Only optimize AND for now.
+  // Only optimize AND for now.
   if (Op.getOpcode() != ISD::AND)
     return false;
 
@@ -20188,29 +20188,27 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
     return false;
 
   unsigned Mask = C->getZExtValue();
-  
+
   if (Mask == 0 || Mask == ~0U)
     return false;
-    
-  unsigned Mask = C->getZExtValue();
 
   unsigned Demanded = DemandedBits.getZExtValue();
   unsigned ShrunkMask = Mask & Demanded;
   unsigned ExpandedMask = Mask | ~Demanded;
 
-    auto IsLegalMask = [ShrunkMask, ExpandedMask](unsigned Mask) -> bool {
-      return (ShrunkMask & Mask) == ShrunkMask && (~ExpandedMask & Mask) == 0;
-    };
-    auto UseMask = [Mask, Op, VT, &TLO](unsigned NewMask) -> bool {
-      if (NewMask == Mask)
-        return true;
-      SDLoc DL(Op);
-      SDValue NewC = TLO.DAG.getConstant(NewMask, DL, VT);
-      SDValue NewOp = TLO.DAG.getNode(ISD::AND, DL, VT, Op.getOperand(0), NewC);
-      return TLO.CombineTo(Op, NewOp);
-    };
+  auto IsLegalMask = [ShrunkMask, ExpandedMask](unsigned Mask) -> bool {
+    return (ShrunkMask & Mask) == ShrunkMask && (~ExpandedMask & Mask) == 0;
+  };
+  auto UseMask = [Mask, Op, VT, &TLO](unsigned NewMask) -> bool {
+    if (NewMask == Mask)
+      return true;
+    SDLoc DL(Op);
+    SDValue NewC = TLO.DAG.getConstant(NewMask, DL, VT);
+    SDValue NewOp = TLO.DAG.getNode(ISD::AND, DL, VT, Op.getOperand(0), NewC);
+    return TLO.CombineTo(Op, NewOp);
+  };
 
-      // If thumb, check for uxth and uxtb masks first and foremost.
+  // If thumb, check for uxth and uxtb masks first and foremost.
   if (Subtarget->isThumb1Only() && Subtarget->hasV6Ops()) {
     if (IsLegalMask(0xFF)) {
       ++NumOptimizedImms;
@@ -20227,17 +20225,23 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
   // result with zero.
   if (ShrunkMask == 0) {
     ++NumOptimizedImms;
-    return UseMask(0);
+    return UseMask(ShrunkMask);
   }
 
   // If the mask is all ones, erase the AND. (Currently, the target-independent
   // code won't do this, so we have to do it explicitly to avoid an infinite
   // loop in obscure cases.)
   if (ExpandedMask == ~0U) {
     ++NumOptimizedImms;
-    return TLO.CombineTo(Op, Op.getOperand(0));
+    return UseMask(ExpandedMask);
   }
 
+  // Don't optimize if it is legal already.
+  if (isLegalLogicalImmediate(Mask, Subtarget))
+    return false;
+
+  if (isLegalLogicalImmediate(~Mask, Subtarget))
+    return UseMask(Mask); // FIXME: Returning false causes infinite loop.
 
   if (isLegalLogicalImmediate(ShrunkMask, Subtarget)) {
     ++NumOptimizedImms;
@@ -20249,13 +20253,6 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
     return UseMask(ExpandedMask);
   }
 
-  // Don't optimize if it is legal already.
-  if (isLegalLogicalImmediate(Mask, Subtarget))
-    return false;
-
-  if (isLegalLogicalImmediate(~Mask, Subtarget))
-    return UseMask(Mask); // FIXME: Returning false causes infinite loop.
-
   // Potential improvements:
   //
   // We could try to recognize lsls+lsrs or lsrs+lsls pairs here.