implement PR9315, constant folding exp2 in terms of pow (since hosts without

C99 runtimes don't have exp2).

llvm-svn: 131872

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 5de2b04e80d..08a6065b31a 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1085,7 +1085,7 @@ llvm::canConstantFoldCallTo(const Function *F) {
   case 'c':
     return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
   case 'e':
-    return Name == "exp";
+    return Name == "exp" || Name == "exp2";
   case 'f':
     return Name == "fabs" || Name == "fmod" || Name == "floor";
   case 'l':
@@ -1221,6 +1221,12 @@ llvm::ConstantFoldCall(Function *F,
       case 'e':
         if (Name == "exp")
           return ConstantFoldFP(exp, V, Ty);
+  
+        if (Name == "exp2") {
+          // Constant fold exp2(x) as pow(2,x) in case the host doesn't have a
+          // C99 library.
+          return ConstantFoldBinaryFP(pow, 2.0, V, Ty);
+        }
         break;
       case 'f':
         if (Name == "fabs")