[InstCombine] Pass SimplifyQuery to SimplifyDemandedBits()

This will enable calling SimplifyDemandedBits() with a SimplifyQuery
that has CondContext set in the future.

Additionally this also marginally strengthens the analysis by
retaining the original context instruction for one-use chains.

Author: nikic

llvm/include/llvm/Transforms/InstCombine/InstCombiner.h

@@ -504,7 +504,14 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner {
 
   virtual bool SimplifyDemandedBits(Instruction *I, unsigned OpNo,
                                     const APInt &DemandedMask, KnownBits &Known,
-                                    unsigned Depth = 0) = 0;
+                                    unsigned Depth, const SimplifyQuery &Q) = 0;
+
+  bool SimplifyDemandedBits(Instruction *I, unsigned OpNo,
+                            const APInt &DemandedMask, KnownBits &Known) {
+    return SimplifyDemandedBits(I, OpNo, DemandedMask, Known,
+                                /*Depth=*/0, SQ.getWithInstruction(I));
+  }
+
   virtual Value *
   SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, APInt &UndefElts,
                              unsigned Depth = 0,

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -187,7 +187,7 @@ ARMTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
     }
     KnownBits ScalarKnown(32);
     if (IC.SimplifyDemandedBits(&II, 0, APInt::getLowBitsSet(32, 16),
-                                ScalarKnown, 0)) {
+                                ScalarKnown)) {
       return ⅈ
     }
     break;

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -6451,13 +6451,13 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
     // Don't use dominating conditions when folding icmp using known bits. This
     // may convert signed into unsigned predicates in ways that other passes
     // (especially IndVarSimplify) may not be able to reliably undo.
-    SQ.DC = nullptr;
-    auto _ = make_scope_exit([&]() { SQ.DC = &DC; });
+    SimplifyQuery Q = SQ.getWithoutDomCondCache().getWithInstruction(&I);
     if (SimplifyDemandedBits(&I, 0, getDemandedBitsLHSMask(I, BitWidth),
-                             Op0Known, 0))
+                             Op0Known, /*Depth=*/0, Q))
       return &I;
 
-    if (SimplifyDemandedBits(&I, 1, APInt::getAllOnes(BitWidth), Op1Known, 0))
+    if (SimplifyDemandedBits(&I, 1, APInt::getAllOnes(BitWidth), Op1Known,
+                             /*Depth=*/0, Q))
       return &I;
   }
 

llvm/lib/Transforms/InstCombine/InstCombineInternal.h

@@ -548,18 +548,19 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
   /// Attempts to replace V with a simpler value based on the demanded
   /// bits.
   Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, KnownBits &Known,
-                                 unsigned Depth, Instruction *CxtI);
+                                 unsigned Depth, const SimplifyQuery &Q);
+  using InstCombiner::SimplifyDemandedBits;
   bool SimplifyDemandedBits(Instruction *I, unsigned Op,
                             const APInt &DemandedMask, KnownBits &Known,
-                            unsigned Depth = 0) override;
+                            unsigned Depth, const SimplifyQuery &Q) override;
 
   /// Helper routine of SimplifyDemandedUseBits. It computes KnownZero/KnownOne
   /// bits. It also tries to handle simplifications that can be done based on
   /// DemandedMask, but without modifying the Instruction.
   Value *SimplifyMultipleUseDemandedBits(Instruction *I,
                                          const APInt &DemandedMask,
-                                         KnownBits &Known,
-                                         unsigned Depth, Instruction *CxtI);
+                                         KnownBits &Known, unsigned Depth,
+                                         const SimplifyQuery &Q);
 
   /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
   /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.