InstSimplify: Optimize away useless unsigned comparisons

[oota-llvm.git] / lib / IR / ConstantFold.cpp

diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp
index b96d1540d715547e98d5ff89a32178e1cd620674..b28effee812aeabc645816ae936d02bfa9d7cc05 100644 (file)
--- a/lib/IR/ConstantFold.cpp
+++ b/lib/IR/ConstantFold.cpp
@@ -593,8 +593,13 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
       bool ignored;
       uint64_t x[2]; 
       uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
-      (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
-                                APFloat::rmTowardZero, &ignored);
+      if (APFloat::opInvalidOp ==
+          V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
+                             APFloat::rmTowardZero, &ignored)) {
+        // Undefined behavior invoked - the destination type can't represent
+        // the input constant.
+        return UndefValue::get(DestTy);
+      }
       APInt Val(DestBitWidth, x);
       return ConstantInt::get(FPC->getContext(), Val);
     }
@@ -653,9 +658,13 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
       APInt api = CI->getValue();
       APFloat apf(DestTy->getFltSemantics(),
                   APInt::getNullValue(DestTy->getPrimitiveSizeInBits()));
-      (void)apf.convertFromAPInt(api, 
-                                 opc==Instruction::SIToFP,
-                                 APFloat::rmNearestTiesToEven);
+      if (APFloat::opOverflow &
+          apf.convertFromAPInt(api, opc==Instruction::SIToFP,
+                              APFloat::rmNearestTiesToEven)) {
+        // Undefined behavior invoked - the destination type can't represent
+        // the input constant.
+        return UndefValue::get(DestTy);
+      }
       return ConstantFP::get(V->getContext(), apf);
     }
     return nullptr;
@@ -1341,7 +1350,7 @@ static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
                                                       const GlobalValue *GV2) {
   // Don't try to decide equality of aliases.
   if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
-    if (!GV1->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage())
+    if (!GV1->hasExternalWeakLinkage() && !GV2->hasExternalWeakLinkage())
       return ICmpInst::ICMP_NE;
   return ICmpInst::BAD_ICMP_PREDICATE;
 }