Rip min/max pattern matching out of InstCombine and into

 ValueTracking.

This matching functionality is useful in more than just InstCombine, so
make it available in ValueTracking.

NFC.

llvm-svn: 236998

1 files changed, 4 insertions, 88 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 6e57faa..b13d3ed 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -14,6 +14,7 @@
 #include "InstCombineInternal.h"
 #include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/PatternMatch.h"
 using namespace llvm;
 using namespace PatternMatch;
@@ -60,91 +61,6 @@ static Value *generateMinMaxSelectPattern(InstCombiner::BuilderTy *Builder,
   return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B);
 }
 
-/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
-/// returning the kind and providing the out parameter results if we
-/// successfully match.
-static SelectPatternFlavor
-MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
-  SelectInst *SI = dyn_cast<SelectInst>(V);
-  if (!SI) return SPF_UNKNOWN;
-
-  ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
-  if (!ICI) return SPF_UNKNOWN;
-
-  ICmpInst::Predicate Pred = ICI->getPredicate();
-  Value *CmpLHS = ICI->getOperand(0);
-  Value *CmpRHS = ICI->getOperand(1);
-  Value *TrueVal = SI->getTrueValue();
-  Value *FalseVal = SI->getFalseValue();
-
-  LHS = CmpLHS;
-  RHS = CmpRHS;
-
-  // (icmp X, Y) ? X : Y
-  if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
-    switch (Pred) {
-    default: return SPF_UNKNOWN; // Equality.
-    case ICmpInst::ICMP_UGT:
-    case ICmpInst::ICMP_UGE: return SPF_UMAX;
-    case ICmpInst::ICMP_SGT:
-    case ICmpInst::ICMP_SGE: return SPF_SMAX;
-    case ICmpInst::ICMP_ULT:
-    case ICmpInst::ICMP_ULE: return SPF_UMIN;
-    case ICmpInst::ICMP_SLT:
-    case ICmpInst::ICMP_SLE: return SPF_SMIN;
-    }
-  }
-
-  // (icmp X, Y) ? Y : X
-  if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
-    switch (Pred) {
-    default: return SPF_UNKNOWN; // Equality.
-    case ICmpInst::ICMP_UGT:
-    case ICmpInst::ICMP_UGE: return SPF_UMIN;
-    case ICmpInst::ICMP_SGT:
-    case ICmpInst::ICMP_SGE: return SPF_SMIN;
-    case ICmpInst::ICMP_ULT:
-    case ICmpInst::ICMP_ULE: return SPF_UMAX;
-    case ICmpInst::ICMP_SLT:
-    case ICmpInst::ICMP_SLE: return SPF_SMAX;
-    }
-  }
-
-  if (ConstantInt *C1 = dyn_cast<ConstantInt>(CmpRHS)) {
-    if ((CmpLHS == TrueVal && match(FalseVal, m_Neg(m_Specific(CmpLHS)))) ||
-        (CmpLHS == FalseVal && match(TrueVal, m_Neg(m_Specific(CmpLHS))))) {
-
-      // ABS(X) ==> (X >s 0) ? X : -X and (X >s -1) ? X : -X
-      // NABS(X) ==> (X >s 0) ? -X : X and (X >s -1) ? -X : X
-      if (Pred == ICmpInst::ICMP_SGT && (C1->isZero() || C1->isMinusOne())) {
-        return (CmpLHS == TrueVal) ? SPF_ABS : SPF_NABS;
-      }
-
-      // ABS(X) ==> (X <s 0) ? -X : X and (X <s 1) ? -X : X
-      // NABS(X) ==> (X <s 0) ? X : -X and (X <s 1) ? X : -X
-      if (Pred == ICmpInst::ICMP_SLT && (C1->isZero() || C1->isOne())) {
-        return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS;
-      }
-    }
-
-    // Y >s C ? ~Y : ~C == ~Y <s ~C ? ~Y : ~C = SMIN(~Y, ~C)
-    if (const auto *C2 = dyn_cast<ConstantInt>(FalseVal)) {
-      if (C1->getType() == C2->getType() && ~C1->getValue() == C2->getValue() &&
-          (match(TrueVal, m_Not(m_Specific(CmpLHS))) ||
-           match(CmpLHS, m_Not(m_Specific(TrueVal))))) {
-        LHS = TrueVal;
-        RHS = FalseVal;
-        return SPF_SMIN;
-      }
-    }
-  }
-
-  // TODO: (X > 4) ? X : 5   -->  (X >= 5) ? X : 5  -->  MAX(X, 5)
-
-  return SPF_UNKNOWN;
-}
-
-
 /// GetSelectFoldableOperands - We want to turn code that looks like this:
 ///   %C = or %A, %B
 ///   %D = select %cond, %C, %A
@@ -1243,18 +1159,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
       return FoldI;
 
     Value *LHS, *RHS, *LHS2, *RHS2;
-    SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS);
+    SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS);
 
     // MAX(MAX(a, b), a) -> MAX(a, b)
     // MIN(MIN(a, b), a) -> MIN(a, b)
     // MAX(MIN(a, b), a) -> a
     // MIN(MAX(a, b), a) -> a
     if (SPF) {
-      if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
+      if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
         if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
                                           SI, SPF, RHS))
           return R;
-      if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
+      if (SelectPatternFlavor SPF2 = matchSelectPattern(RHS, LHS2, RHS2))
         if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
                                           SI, SPF, LHS))
           return R;