[InstCombine] add helper functions for foldICmpWithConstant; NFCI

Besides breaking up a 700 line function to improve readability,
this sinks the 'FIXME: ConstantInt' check into each helper. So 
now we can independently break that restriction within any of the
helper functions.

As much as possible, the code was only {cut/paste/clang-format}'ed 
to minimize risk (no functional changes intended), so several more
readability improvements are still possible. 

llvm-svn: 278828
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 88c52e2..7ce5ac1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -548,10 +548,10 @@
                                             ConstantInt *AndCst = nullptr);
   Instruction *foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
                                     Constant *RHSC);
-  Instruction *foldICmpDivConst(ICmpInst &ICI, BinaryOperator *DivI,
-                                ConstantInt *DivRHS);
-  Instruction *foldICmpShrConst(ICmpInst &ICI, BinaryOperator *DivI,
-                                ConstantInt *DivRHS);
+  Instruction *foldICmpDivConstConst(ICmpInst &ICI, BinaryOperator *DivI,
+                                     ConstantInt *DivRHS);
+  Instruction *foldICmpShrConstConst(ICmpInst &ICI, BinaryOperator *DivI,
+                                     ConstantInt *DivRHS);
   Instruction *foldICmpCstShrConst(ICmpInst &I, Value *Op, Value *A,
                                    ConstantInt *CI1, ConstantInt *CI2);
   Instruction *foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
@@ -560,6 +560,30 @@
                                   ICmpInst::Predicate Pred);
   Instruction *foldICmpWithCastAndCast(ICmpInst &ICI);
   Instruction *foldICmpWithConstant(ICmpInst &ICI);
+
+  Instruction *foldICmpTruncConstant(ICmpInst &ICI, Instruction *LHSI,
+                                     const APInt *RHSV);
+  Instruction *foldICmpAndConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpXorConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpOrConstant(ICmpInst &ICI, Instruction *LHSI,
+                                  const APInt *RHSV);
+  Instruction *foldICmpMulConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpShlConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpShrConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpUDivConstant(ICmpInst &ICI, Instruction *LHSI,
+                                    const APInt *RHSV);
+  Instruction *foldICmpDivConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpSubConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+  Instruction *foldICmpAddConstant(ICmpInst &ICI, Instruction *LHSI,
+                                   const APInt *RHSV);
+
   Instruction *foldICmpEqualityWithConstant(ICmpInst &ICI);
   Instruction *foldICmpIntrinsicWithConstant(ICmpInst &ICI);