instcombine: Migrate isdigit optimizations

This patch migrates the isdigit optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168578 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index ec98e93b29..1320f70097 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1267,6 +1267,22 @@ struct AbsOpt : public LibCallOptimization {
   }
 };
 
+struct IsDigitOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    FunctionType *FT = Callee->getFunctionType();
+    // We require integer(i32)
+    if (FT->getNumParams() != 1 || !FT->getReturnType()->isIntegerTy() ||
+        !FT->getParamType(0)->isIntegerTy(32))
+      return 0;
+
+    // isdigit(c) -> (c-'0') <u 10
+    Value *Op = CI->getArgOperand(0);
+    Op = B.CreateSub(Op, B.getInt32('0'), "isdigittmp");
+    Op = B.CreateICmpULT(Op, B.getInt32(10), "isdigit");
+    return B.CreateZExt(Op, CI->getType());
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -1316,6 +1332,7 @@ class LibCallSimplifierImpl {
   // Integer library call optimizations.
   FFSOpt FFS;
   AbsOpt Abs;
+  IsDigitOpt IsDigit;
 
   void initOptimizations();
   void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@@ -1434,6 +1451,7 @@ void LibCallSimplifierImpl::initOptimizations() {
   addOpt(LibFunc::abs, &Abs);
   addOpt(LibFunc::labs, &Abs);
   addOpt(LibFunc::llabs, &Abs);
+  addOpt(LibFunc::isdigit, &IsDigit);
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {