[PartialInliner] Inline vararg functions that forward varargs.

Summary:
This patch extends the partial inliner to support inlining parts of
vararg functions, if the vararg handling is done in the outlined part.

It adds a `ForwardVarArgsTo` argument to InlineFunction. If it is
non-null, all varargs passed to the inlined function will be added to
all calls to `ForwardVarArgsTo`.

The partial inliner takes care to only pass `ForwardVarArgsTo` if the
varargs handing is done in the outlined function. It checks that vastart
is not part of the function to be inlined.

`test/Transforms/CodeExtractor/PartialInlineNoInline.ll` (already part
of the repo) checks we do not do partial inlining if vastart is used in
a basic block that will be inlined.

Reviewers: davide, davidxl, grosser

Reviewed By: davide, davidxl, grosser

Subscribers: gyiu, grosser, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D39607

llvm-svn: 318028

1 files changed, 9 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/IPO/PartialInlining.cpp b/llvm/lib/Transforms/IPO/PartialInlining.cpp
index c47d8b78df3..c00e13c4ae2 100644
--- a/llvm/lib/Transforms/IPO/PartialInlining.cpp
+++ b/llvm/lib/Transforms/IPO/PartialInlining.cpp
@@ -149,7 +149,12 @@ struct PartialInlinerImpl {
     // the return block.
     void NormalizeReturnBlock();
 
-    // Do function outlining:
+    // Do function outlining.
+    // NOTE: For vararg functions that do the vararg handling in the outlined
+    //       function, we temporarily generate IR that does not properly
+    //       forward varargs to the outlined function. Calling InlineFunction
+    //       will update calls to the outlined functions to properly forward
+    //       the varargs.
     Function *doFunctionOutlining();
 
     Function *OrigFunc = nullptr;
@@ -813,7 +818,8 @@ Function *PartialInlinerImpl::FunctionCloner::doFunctionOutlining() {
 
   // Extract the body of the if.
   OutlinedFunc = CodeExtractor(ToExtract, &DT, /*AggregateArgs*/ false,
-                               ClonedFuncBFI.get(), &BPI)
+                               ClonedFuncBFI.get(), &BPI,
+                               /* AllowVarargs */ true)
                      .extractCodeRegion();
 
   if (OutlinedFunc) {
@@ -938,7 +944,7 @@ bool PartialInlinerImpl::tryPartialInline(FunctionCloner &Cloner) {
        << ore::NV("Caller", CS.getCaller());
 
     InlineFunctionInfo IFI(nullptr, GetAssumptionCache, PSI);
-    if (!InlineFunction(CS, IFI))
+    if (!InlineFunction(CS, IFI, nullptr, true, Cloner.OutlinedFunc))
       continue;
 
     ORE.emit(OR);