[InstCombine] Expand the simplification of pow() with nested exp{,2}()

Expand the simplification of `pow(exp{,2}(x), y)` to all FP types.

This improvement helps some benchmarks in SPEC CPU2000 and CPU2006, such as
252.eon, 447.dealII, 453.povray.  Otherwise, no significant regressions on
x86-64 or A64.

Differential revision: https://reviews.llvm.org/D51195

llvm-svn: 340948

1 files changed, 21 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index b0ee1fa0299..6c359ebf2b8 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1212,14 +1212,31 @@ Value *LibCallSimplifier::replacePowWithExp(CallInst *Pow, IRBuilder<> &B) {
     LibFunc LibFn;
 
     Function *CalleeFn = BaseFn->getCalledFunction();
-    if (CalleeFn && TLI->getLibFunc(CalleeFn->getName(), LibFn) &&
-        (LibFn == LibFunc_exp || LibFn == LibFunc_exp2) && TLI->has(LibFn)) {
+    if (CalleeFn &&
+        TLI->getLibFunc(CalleeFn->getName(), LibFn) && TLI->has(LibFn)) {
+      StringRef ExpName;
+      Intrinsic::ID ID;
       Value *ExpFn;
 
+      switch (LibFn) {
+      default:
+        return nullptr;
+      case LibFunc_expf:  case LibFunc_exp:  case LibFunc_expl:
+        ExpName = TLI->getName(LibFunc_exp);
+        ID = Intrinsic::exp;
+        break;
+      case LibFunc_exp2f: case LibFunc_exp2: case LibFunc_exp2l:
+        ExpName = TLI->getName(LibFunc_exp2);
+        ID = Intrinsic::exp2;
+        break;
+      }
+
       // Create new exp{,2}() with the product as its argument.
       Value *FMul = B.CreateFMul(BaseFn->getArgOperand(0), Expo, "mul");
-      ExpFn = emitUnaryFloatFnCall(FMul, CalleeFn->getName(), B,
-                                   BaseFn->getAttributes());
+      ExpFn = BaseFn->doesNotAccessMemory()
+              ? B.CreateCall(Intrinsic::getDeclaration(Mod, ID, Ty),
+                             FMul, ExpName)
+              : emitUnaryFloatFnCall(FMul, ExpName, B, BaseFn->getAttributes());
 
       // Since the new exp{,2}() is different from the original one, dead code
       // elimination cannot be trusted to remove it, since it may have side