Provide reason messages for unviable inlining

InlineCost's isInlineViable() is changed to return InlineResult
instead of bool. This provides messages for failure reasons and
allows to get more specific messages for cases where callsites
are not viable for inlining.

Reviewed By: xbolva00, anemet

Differential Revision: https://reviews.llvm.org/D57089

llvm-svn: 352849

1 files changed, 15 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/IPO/AlwaysInliner.cpp b/llvm/lib/Transforms/IPO/AlwaysInliner.cpp
index c7697556530..0058bb9832a 100644
--- a/llvm/lib/Transforms/IPO/AlwaysInliner.cpp
+++ b/llvm/lib/Transforms/IPO/AlwaysInliner.cpp
@@ -145,11 +145,20 @@ InlineCost AlwaysInlinerLegacyPass::getInlineCost(CallSite CS) {
   Function *Callee = CS.getCalledFunction();
 
   // Only inline direct calls to functions with always-inline attributes
-  // that are viable for inlining. FIXME: We shouldn't even get here for
-  // declarations.
-  if (Callee && !Callee->isDeclaration() &&
-      CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee))
-    return InlineCost::getAlways("always inliner");
+  // that are viable for inlining.
+  if (!Callee)
+    return InlineCost::getNever("indirect call");
 
-  return InlineCost::getNever("always inliner");
+  // FIXME: We shouldn't even get here for declarations.
+  if (Callee->isDeclaration())
+    return InlineCost::getNever("no definition");
+
+  if (!CS.hasFnAttr(Attribute::AlwaysInline))
+    return InlineCost::getNever("no alwaysinline attribute");
+
+  auto IsViable = isInlineViable(*Callee);
+  if (!IsViable)
+    return InlineCost::getNever(IsViable.message);
+
+  return InlineCost::getAlways("always inliner");
 }