[PATCH] D13377: [SCEV] Refactor out a createNodeForSelect

[Sanjoy Das via llvm-commits]

sanjoy added inline comments.

================
Comment at: lib/Analysis/ScalarEvolution.cpp:4566
@@ -4472,89 +4565,3 @@
   case Instruction::Select:
-    // This could be a smax or umax that was lowered earlier.
-    // Try to recover it.
-    if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
-      Value *LHS = ICI->getOperand(0);
-      Value *RHS = ICI->getOperand(1);
-      switch (ICI->getPredicate()) {
-      case ICmpInst::ICMP_SLT:
-      case ICmpInst::ICMP_SLE:
-        std::swap(LHS, RHS);
-        // fall through
-      case ICmpInst::ICMP_SGT:
-      case ICmpInst::ICMP_SGE:
-        // a >s b ? a+x : b+x  ->  smax(a, b)+x
-        // a >s b ? b+x : a+x  ->  smin(a, b)+x
-        if (getTypeSizeInBits(LHS->getType()) <=
-            getTypeSizeInBits(U->getType())) {
-          const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), U->getType());
-          const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), U->getType());
-          const SCEV *LA = getSCEV(U->getOperand(1));
-          const SCEV *RA = getSCEV(U->getOperand(2));
-          const SCEV *LDiff = getMinusSCEV(LA, LS);
-          const SCEV *RDiff = getMinusSCEV(RA, RS);
-          if (LDiff == RDiff)
-            return getAddExpr(getSMaxExpr(LS, RS), LDiff);
-          LDiff = getMinusSCEV(LA, RS);
-          RDiff = getMinusSCEV(RA, LS);
-          if (LDiff == RDiff)
-            return getAddExpr(getSMinExpr(LS, RS), LDiff);
-        }
-        break;
-      case ICmpInst::ICMP_ULT:
-      case ICmpInst::ICMP_ULE:
-        std::swap(LHS, RHS);
-        // fall through
-      case ICmpInst::ICMP_UGT:
-      case ICmpInst::ICMP_UGE:
-        // a >u b ? a+x : b+x  ->  umax(a, b)+x
-        // a >u b ? b+x : a+x  ->  umin(a, b)+x
-        if (getTypeSizeInBits(LHS->getType()) <=
-            getTypeSizeInBits(U->getType())) {
-          const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
-          const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), U->getType());
-          const SCEV *LA = getSCEV(U->getOperand(1));
-          const SCEV *RA = getSCEV(U->getOperand(2));
-          const SCEV *LDiff = getMinusSCEV(LA, LS);
-          const SCEV *RDiff = getMinusSCEV(RA, RS);
-          if (LDiff == RDiff)
-            return getAddExpr(getUMaxExpr(LS, RS), LDiff);
-          LDiff = getMinusSCEV(LA, RS);
-          RDiff = getMinusSCEV(RA, LS);
-          if (LDiff == RDiff)
-            return getAddExpr(getUMinExpr(LS, RS), LDiff);
-        }
-        break;
-      case ICmpInst::ICMP_NE:
-        // n != 0 ? n+x : 1+x  ->  umax(n, 1)+x
-        if (getTypeSizeInBits(LHS->getType()) <=
-                getTypeSizeInBits(U->getType()) &&
-            isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
-          const SCEV *One = getOne(U->getType());
-          const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
-          const SCEV *LA = getSCEV(U->getOperand(1));
-          const SCEV *RA = getSCEV(U->getOperand(2));
-          const SCEV *LDiff = getMinusSCEV(LA, LS);
-          const SCEV *RDiff = getMinusSCEV(RA, One);
-          if (LDiff == RDiff)
-            return getAddExpr(getUMaxExpr(One, LS), LDiff);
-        }
-        break;
-      case ICmpInst::ICMP_EQ:
-        // n == 0 ? 1+x : n+x  ->  umax(n, 1)+x
-        if (getTypeSizeInBits(LHS->getType()) <=
-                getTypeSizeInBits(U->getType()) &&
-            isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
-          const SCEV *One = getOne(U->getType());
-          const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
-          const SCEV *LA = getSCEV(U->getOperand(1));
-          const SCEV *RA = getSCEV(U->getOperand(2));
-          const SCEV *LDiff = getMinusSCEV(LA, One);
-          const SCEV *RDiff = getMinusSCEV(RA, LS);
-          if (LDiff == RDiff)
-            return getAddExpr(getUMaxExpr(One, LS), LDiff);
-        }
-        break;
-      default:
-        break;
-      }
-    }
+    if (isa<Instruction>(U))
+      return createNodeForSelect(cast<Instruction>(U), U->getOperand(0),
----------------
joker.eph wrote:
> What else than an instruction it could be here?
It could be a `SelectOperator` (a `ConstantExpr`).  These won't have their condition operand be an `icmp` anyway (which is the first thing we check for in `createNodeForSelect`), so ignoring these at this place is fine.

I'll add a comment stating what I just said.


http://reviews.llvm.org/D13377