3 files changed, 45 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 502913886e3..fc7e7d9c3ce 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1581,12 +1581,36 @@ bool TargetLowering::SimplifyDemandedBits(
       if (SimplifyDemandedBits(Src, DemandedSrcBits, DemandedSrcElts,
                                KnownSrcBits, TLO, Depth + 1))
         return true;
+    } else if ((NumSrcEltBits % BitWidth) == 0 &&
+               TLO.DAG.getDataLayout().isLittleEndian()) {
+      unsigned Scale = NumSrcEltBits / BitWidth;
+      unsigned NumSrcElts = SrcVT.isVector() ? SrcVT.getVectorNumElements() : 1;
+      APInt DemandedSrcBits = APInt::getNullValue(NumSrcEltBits);
+      APInt DemandedSrcElts = APInt::getNullValue(NumSrcElts);
+      for (unsigned i = 0; i != NumElts; ++i)
+        if (DemandedElts[i]) {
+          unsigned Offset = (i % Scale) * BitWidth;
+          DemandedSrcBits.insertBits(DemandedBits, Offset);
+          DemandedSrcElts.setBit(i / Scale);
+        }
+
+      if (SrcVT.isVector()) {
+        APInt KnownSrcUndef, KnownSrcZero;
+        if (SimplifyDemandedVectorElts(Src, DemandedSrcElts, KnownSrcUndef,
+                                       KnownSrcZero, TLO, Depth + 1))
+          return true;
+      }
+
+      KnownBits KnownSrcBits;
+      if (SimplifyDemandedBits(Src, DemandedSrcBits, DemandedSrcElts,
+                               KnownSrcBits, TLO, Depth + 1))
+        return true;
     }
 
     // If this is a bitcast, let computeKnownBits handle it.  Only do this on a
     // recursive call where Known may be useful to the caller.
     if (Depth > 0) {
-      Known = TLO.DAG.computeKnownBits(Op, Depth);
+      Known = TLO.DAG.computeKnownBits(Op, DemandedElts, Depth);
       return false;
     }
     break;
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 7dec87cdcb0..1e62958e722 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -216,6 +216,21 @@ X86RegisterInfo::getPointerRegClass(const MachineFunction &MF,
   }
 }
 
+bool X86RegisterInfo::shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
+                                           unsigned DefSubReg,
+                                           const TargetRegisterClass *SrcRC,
+                                           unsigned SrcSubReg) const {
+  // Prevent rewriting a copy where the destination size is larger than the
+  // input size. See PR41619.
+  // FIXME: Should this be factored into the base implementation somehow.
+  if (DefRC->hasSuperClassEq(&X86::GR64RegClass) && DefSubReg == 0 &&
+      SrcRC->hasSuperClassEq(&X86::GR64RegClass) && SrcSubReg == X86::sub_32bit)
+    return false;
+
+  return TargetRegisterInfo::shouldRewriteCopySrc(DefRC, DefSubReg,
+                                                  SrcRC, SrcSubReg);
+}
+
 const TargetRegisterClass *
 X86RegisterInfo::getGPRsForTailCall(const MachineFunction &MF) const {
   const Function &F = MF.getFunction();
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.h b/llvm/lib/Target/X86/X86RegisterInfo.h
index d362f20b472..81e4920f6a5 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.h
+++ b/llvm/lib/Target/X86/X86RegisterInfo.h
@@ -74,6 +74,11 @@ public:
   getLargestLegalSuperClass(const TargetRegisterClass *RC,
                             const MachineFunction &MF) const override;
 
+  bool shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
+                            unsigned DefSubReg,
+                            const TargetRegisterClass *SrcRC,
+                            unsigned SrcSubReg) const override;
+
   /// getPointerRegClass - Returns a TargetRegisterClass used for pointer
   /// values.
   const TargetRegisterClass *