Fold "icmp pred (srem X, Y), Y" like we do for urem. Handle signed comparisons

in the urem case, though not the other way around. This is enough to get #3 from
PR9343!

llvm-svn: 126991

1 files changed, 30 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 3cfb2b7637e..44b0247e5ae 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1671,14 +1671,28 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
     }
   }
 
-  if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
+  Value *V;
+  if (LBO && match(LBO, m_URem(m_Value(V), m_Specific(RHS)))) {
+    bool KnownNonNegative, KnownNegative;
     switch (Pred) {
     default:
       break;
+    case ICmpInst::ICMP_SGT:
+    case ICmpInst::ICMP_SGE:
+      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
+      if (!KnownNonNegative)
+        break;
+      // fall-through
     case ICmpInst::ICMP_EQ:
     case ICmpInst::ICMP_UGT:
     case ICmpInst::ICMP_UGE:
       return ConstantInt::getFalse(RHS->getContext());
+    case ICmpInst::ICMP_SLT:
+    case ICmpInst::ICMP_SLE:
+      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
+      if (!KnownNonNegative)
+        break;
+      // fall-through
     case ICmpInst::ICMP_NE:
     case ICmpInst::ICMP_ULT:
     case ICmpInst::ICMP_ULE:
@@ -1686,6 +1700,21 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
     }
   }
 
+  if (LBO && match(LBO, m_SRem(m_Value(), m_Specific(RHS)))) {
+    switch (Pred) {
+    default:
+      break;
+    case ICmpInst::ICMP_EQ:
+    case ICmpInst::ICMP_SGT:
+    case ICmpInst::ICMP_SGE:
+      return ConstantInt::getFalse(RHS->getContext());
+    case ICmpInst::ICMP_NE:
+    case ICmpInst::ICMP_SLT:
+    case ICmpInst::ICMP_SLE:
+      return ConstantInt::getTrue(RHS->getContext());
+    }
+  }
+
   // If the comparison is with the result of a select instruction, check whether
   // comparing with either branch of the select always yields the same value.
   if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))