Dan recently disabled recursive inlining within a function, but we

were still inlining self-recursive functions into other functions.

Inlining a recursive function into itself has the potential to
reduce recursion depth by a factor of 2, inlining a recursive
function into something else reduces recursion depth by exactly 
1.  Since inlining a recursive function into something else is a
weird form of loop peeling, turn this off.

The deleted testcase was added by Dale in r62107, since then
we're leaning towards not inlining recursive stuff ever.  In any
case, if we like inlining recursive stuff, it should be done 
within the recursive function itself to get the algorithm 
recursion depth win.

llvm-svn: 102798

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index cb9e5526fc4..b478b503ba9 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -159,10 +159,18 @@ void CodeMetrics::analyzeBasicBlock(const BasicBlock *BB) {
       // it.  This is a hack because we depend on the user marking their local
       // variables as volatile if they are live across a setjmp call, and they
       // probably won't do this in callers.
-      if (Function *F = CS.getCalledFunction())
+      if (Function *F = CS.getCalledFunction()) {
         if (F->isDeclaration() && 
             (F->getName() == "setjmp" || F->getName() == "_setjmp"))
           NeverInline = true;
+       
+        // If this call is to function itself, then the function is recursive.
+        // Inlining it into other functions is a bad idea, because this is
+        // basically just a form of loop peeling, and our metrics aren't useful
+        // for that case.
+        if (F == BB->getParent())
+          NeverInline = true;
+      }
 
       if (!isa<IntrinsicInst>(II) && !callIsSmall(CS.getCalledFunction())) {
         // Each argument to a call takes on average one instruction to set up.