[InstCombine] Rename TTI member for clarity (NFC)

There is already a comment on the member and documentation in the
InstCombine contributor guide, but also rename it to make add
an additional speed bump.

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

@@ -49,7 +49,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner {
   /// Only used to call target specific intrinsic combining.
   /// It must **NOT** be used for any other purpose, as InstCombine is a
   /// target-independent canonicalization transform.
-  TargetTransformInfo &TTI;
+  TargetTransformInfo &TTIForTargetIntrinsicsOnly;
 
 public:
   /// Maximum size of array considered when transforming.
@@ -105,7 +105,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner {
                BlockFrequencyInfo *BFI, BranchProbabilityInfo *BPI,
                ProfileSummaryInfo *PSI, const DataLayout &DL,
                ReversePostOrderTraversal<BasicBlock *> &RPOT)
-      : TTI(TTI), Builder(Builder), Worklist(Worklist),
+      : TTIForTargetIntrinsicsOnly(TTI), Builder(Builder), Worklist(Worklist),
         MinimizeSize(MinimizeSize), AA(AA), AC(AC), TLI(TLI), DT(DT), DL(DL),
         SQ(DL, &TLI, &DT, &AC, nullptr, /*UseInstrInfo*/ true,
            /*CanUseUndef*/ true, &DC),

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -155,7 +155,7 @@ std::optional<Instruction *>
 InstCombiner::targetInstCombineIntrinsic(IntrinsicInst &II) {
   // Handle target specific intrinsics
   if (II.getCalledFunction()->isTargetIntrinsic()) {
-    return TTI.instCombineIntrinsic(*this, II);
+    return TTIForTargetIntrinsicsOnly.instCombineIntrinsic(*this, II);
   }
   return std::nullopt;
 }
@@ -165,8 +165,8 @@ std::optional<Value *> InstCombiner::targetSimplifyDemandedUseBitsIntrinsic(
     bool &KnownBitsComputed) {
   // Handle target specific intrinsics
   if (II.getCalledFunction()->isTargetIntrinsic()) {
-    return TTI.simplifyDemandedUseBitsIntrinsic(*this, II, DemandedMask, Known,
-                                                KnownBitsComputed);
+    return TTIForTargetIntrinsicsOnly.simplifyDemandedUseBitsIntrinsic(
+        *this, II, DemandedMask, Known, KnownBitsComputed);
   }
   return std::nullopt;
 }
@@ -178,15 +178,18 @@ std::optional<Value *> InstCombiner::targetSimplifyDemandedVectorEltsIntrinsic(
         SimplifyAndSetOp) {
   // Handle target specific intrinsics
   if (II.getCalledFunction()->isTargetIntrinsic()) {
-    return TTI.simplifyDemandedVectorEltsIntrinsic(
+    return TTIForTargetIntrinsicsOnly.simplifyDemandedVectorEltsIntrinsic(
         *this, II, DemandedElts, PoisonElts, PoisonElts2, PoisonElts3,
         SimplifyAndSetOp);
   }
   return std::nullopt;
 }
 
 bool InstCombiner::isValidAddrSpaceCast(unsigned FromAS, unsigned ToAS) const {
-  return TTI.isValidAddrSpaceCast(FromAS, ToAS);
+  // Approved exception for TTI use: This queries a legality property of the
+  // target, not an profitability heuristic. Ideally this should be part of
+  // DataLayout instead.
+  return TTIForTargetIntrinsicsOnly.isValidAddrSpaceCast(FromAS, ToAS);
 }
 
 Value *InstCombinerImpl::EmitGEPOffset(GEPOperator *GEP, bool RewriteGEP) {