[InstSimplify] use ConstantRange to simplify or-of-icmps

We can simplify (or (icmp X, C1), (icmp X, C2)) to 'true' or one of the icmps in many cases.
I had to check some of these with Alive to prove to myself it's right, but everything seems 
to check out. Eg, the deleted code in instcombine was completely ignoring predicates with
mismatched signedness.

This is a follow-up to:
https://reviews.llvm.org/rL301260
https://reviews.llvm.org/D32143

llvm-svn: 302370

1 files changed, 2 insertions, 55 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index c7092bf3a39..b114801cc1c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1834,25 +1834,8 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
     case ICmpInst::ICMP_UGT: // (X == 13 | X u> 14) -> no change
     case ICmpInst::ICMP_SGT: // (X == 13 | X s> 14) -> no change
       break;
-    case ICmpInst::ICMP_NE:  // (X == 13 | X != 15) -> X != 15
-    case ICmpInst::ICMP_ULT: // (X == 13 | X u< 15) -> X u< 15
-    case ICmpInst::ICMP_SLT: // (X == 13 | X s< 15) -> X s< 15
-      return RHS;
     }
     break;
-  case ICmpInst::ICMP_NE:
-    switch (PredR) {
-    default:
-      llvm_unreachable("Unknown integer condition code!");
-    case ICmpInst::ICMP_EQ:  // (X != 13 | X == 15) -> X != 13
-    case ICmpInst::ICMP_UGT: // (X != 13 | X u> 15) -> X != 13
-    case ICmpInst::ICMP_SGT: // (X != 13 | X s> 15) -> X != 13
-      return LHS;
-    case ICmpInst::ICMP_NE:  // (X != 13 | X != 15) -> true
-    case ICmpInst::ICMP_ULT: // (X != 13 | X u< 15) -> true
-    case ICmpInst::ICMP_SLT: // (X != 13 | X s< 15) -> true
-      return Builder->getTrue();
-    }
   case ICmpInst::ICMP_ULT:
     switch (PredR) {
     default:
@@ -1860,15 +1843,9 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
     case ICmpInst::ICMP_EQ: // (X u< 13 | X == 14) -> no change
       break;
     case ICmpInst::ICMP_UGT: // (X u< 13 | X u> 15) -> (X-13) u> 2
-      // If RHSC is [us]MAXINT, it is always false.  Not handling
-      // this can cause overflow.
-      if (RHSC->isMaxValue(false))
-        return LHS;
+      assert(!RHSC->isMaxValue(false) && "Missed icmp simplification");
       return insertRangeTest(LHS0, LHSC->getValue(), RHSC->getValue() + 1,
                              false, false);
-    case ICmpInst::ICMP_NE:  // (X u< 13 | X != 15) -> X != 15
-    case ICmpInst::ICMP_ULT: // (X u< 13 | X u< 15) -> X u< 15
-      return RHS;
     }
     break;
   case ICmpInst::ICMP_SLT:
@@ -1878,39 +1855,9 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
     case ICmpInst::ICMP_EQ: // (X s< 13 | X == 14) -> no change
       break;
     case ICmpInst::ICMP_SGT: // (X s< 13 | X s> 15) -> (X-13) s> 2
-      // If RHSC is [us]MAXINT, it is always false.  Not handling
-      // this can cause overflow.
-      if (RHSC->isMaxValue(true))
-        return LHS;
+      assert(!RHSC->isMaxValue(true) && "Missed icmp simplification");
       return insertRangeTest(LHS0, LHSC->getValue(), RHSC->getValue() + 1, true,
                              false);
-    case ICmpInst::ICMP_NE:  // (X s< 13 | X != 15) -> X != 15
-    case ICmpInst::ICMP_SLT: // (X s< 13 | X s< 15) -> X s< 15
-      return RHS;
-    }
-    break;
-  case ICmpInst::ICMP_UGT:
-    switch (PredR) {
-    default:
-      llvm_unreachable("Unknown integer condition code!");
-    case ICmpInst::ICMP_EQ:  // (X u> 13 | X == 15) -> X u> 13
-    case ICmpInst::ICMP_UGT: // (X u> 13 | X u> 15) -> X u> 13
-      return LHS;
-    case ICmpInst::ICMP_NE:  // (X u> 13 | X != 15) -> true
-    case ICmpInst::ICMP_ULT: // (X u> 13 | X u< 15) -> true
-      return Builder->getTrue();
-    }
-    break;
-  case ICmpInst::ICMP_SGT:
-    switch (PredR) {
-    default:
-      llvm_unreachable("Unknown integer condition code!");
-    case ICmpInst::ICMP_EQ:  // (X s> 13 | X == 15) -> X > 13
-    case ICmpInst::ICMP_SGT: // (X s> 13 | X s> 15) -> X > 13
-      return LHS;
-    case ICmpInst::ICMP_NE:  // (X s> 13 | X != 15) -> true
-    case ICmpInst::ICMP_SLT: // (X s> 13 | X s< 15) -> true
-      return Builder->getTrue();
     }
     break;
   }