Cherry-picking the pow-for-le32 fix from upstream clang.

SVN log from upstream clang:

r185568 | eliben | 2013-07-03 12:19:12 -0700 (Wed, 03 Jul 2013)

Add target hook CodeGen queries when generating builtin pow*.

Without fmath-errno, Clang currently generates calls to @llvm.pow.* intrinsics
when it sees pow*(). This may not be suitable for all targets (for
example le32/PNaCl), so the attached patch adds a target hook that CodeGen
queries. The target can state its preference for having or not having the
intrinsic generated. Non-PNaCl behavior remains unchanged;
PNaCl-specific test added.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3513
R=dschuff@chromium.org

Review URL: https://codereview.chromium.org/18953003

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/CodeGen/CGBuiltin.cpp b/lib/CodeGen/CGBuiltin.cpp
index 7f1709e10f..0d5be26a5e 100644
--- a/lib/CodeGen/CGBuiltin.cpp
+++ b/lib/CodeGen/CGBuiltin.cpp
@@ -1293,10 +1293,17 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
   case Builtin::BIpow:
   case Builtin::BIpowf:
   case Builtin::BIpowl: {
-    // LOCALMOD: For PNACl we don't want pow* calls to ever turn into
-    // intrinsics. We want them to be resolved vs. the newlib implementation
-    // within the pexe during bitcode linking.
-    // TODO(eliben): upstream this
+    // Transform a call to pow* into a @llvm.pow.* intrinsic call, but only
+    // if the target agrees.
+    if (getTargetHooks().emitIntrinsicForPow()) {
+      if (!FD->hasAttr<ConstAttr>())
+        break;
+      Value *Base = EmitScalarExpr(E->getArg(0));
+      Value *Exponent = EmitScalarExpr(E->getArg(1));
+      llvm::Type *ArgType = Base->getType();
+      Value *F = CGM.getIntrinsic(Intrinsic::pow, ArgType);
+      return RValue::get(Builder.CreateCall2(F, Base, Exponent));
+    }
     break;
   }