[PowerPC] Add comment explaining preprocessor directive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187320 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/PPCJITInfo.cpp b/lib/Target/PowerPC/PPCJITInfo.cpp
index 18f4adf839e3ccad8f69f656310624c0a10d5617..5e3a48d8bbdb15cbc83ede21ea67cc9e4b203bd4 100644 (file)
--- a/lib/Target/PowerPC/PPCJITInfo.cpp
+++ b/lib/Target/PowerPC/PPCJITInfo.cpp
@@ -71,6 +71,8 @@ static void EmitBranchToAt(uint64_t At, uint64_t To, bool isCall, bool is64Bit){
 extern "C" void PPC32CompilationCallback();
 extern "C" void PPC64CompilationCallback();
 
+// The first clause of the preprocessor directive looks wrong, but it is
+// necessary when compiling this code on non-PowerPC hosts.
 #if (!defined(__ppc__) && !defined(__powerpc__)) || defined(__powerpc64__) || defined(__ppc64__)
 void PPC32CompilationCallback() {
   llvm_unreachable("This is not a 32bit PowerPC, you can't execute this!");