[Inliner] Don't inline through callsites with operand bundles

[sanjoy]

Summary

This change teaches the LLVM inliner to not inline through callsites
with unknown operand bundles. Currently all operand bundles are
"unknown" operand bundles but in the near future we will add support for
inlining through some select kinds of operand bundles.

[majnemer]

LGTM

lib/Transforms/Utils/InlineFunction.cpp

bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
   // If IFI has any state in it, zap it before we fill it in.
   IFI.reset();
   
   const Function *CalledFunc = CS.getCalledFunction();
   if (!CalledFunc ||              // Can't inline external function or indirect
       CalledFunc->isDeclaration() || // call, or call to a vararg function!
       CalledFunc->getFunctionType()->isVarArg()) return false;
 
+  // The inliner does not know how to inline through calls with operand bundles.
+  if (CS.hasOperandBundles())
+    return false;
+
   // If the call to the callee cannot throw, set the 'nounwind' flag on any
   // calls that we inline.
   bool MarkNoUnwind = CS.doesNotThrow();
 
   BasicBlock *OrigBB = TheCall->getParent();
   Function *Caller = OrigBB->getParent();
 
   // GC poses two hazards to inlining, which only occur when the callee has GC:

test/Feature/OperandBundles/inliner-conservative.ll

+; RUN: opt -S -inline < %s | FileCheck %s
+
+; Check that the inliner does not inline through arbitrary unknown
+; operand bundles.
+
+define i32 @callee() {
+ entry:
+  ret i32 2
+}
+
+define i32 @caller() {
+; CHECK: @caller(
+ entry:
+; CHECK: call i32 @callee() [ "unknown"() ]
+  %x = call i32 @callee() [ "unknown"() ]
+  ret i32 %x
+}