From 28252b6f0a483ffb0ead991c7a1ead14e3cd2fc1 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sun, 16 Jan 2011 08:09:24 +0000
Subject: fix PR8932, a case where arg promotion could infinitely promote.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123574 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/ArgumentPromotion.cpp | 75 ++++++++++++++++++++++----------
 1 file changed, 51 insertions(+), 24 deletions(-)

(limited to 'lib/Transforms/IPO/ArgumentPromotion.cpp')

diff --git a/lib/Transforms/IPO/ArgumentPromotion.cpp b/lib/Transforms/IPO/ArgumentPromotion.cpp
index 17ef703..0c650cf 100644
--- a/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -135,47 +135,74 @@ CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
   if (PointerArgs.empty()) return 0;
 
   // Second check: make sure that all callers are direct callers.  We can't
-  // transform functions that have indirect callers.
-  if (F->hasAddressTaken())
-    return 0;
-
+  // transform functions that have indirect callers.  Also see if the function
+  // is self-recursive.
+  bool isSelfRecursive = false;
+  for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
+       UI != E; ++UI) {
+    CallSite CS(*UI);
+    // Must be a direct call.
+    if (CS.getInstruction() == 0 || !CS.isCallee(UI)) return 0;
+    
+    if (CS.getInstruction()->getParent()->getParent() == F)
+      isSelfRecursive = true;
+  }
+  
   // Check to see which arguments are promotable.  If an argument is promotable,
   // add it to ArgsToPromote.
   SmallPtrSet<Argument*, 8> ArgsToPromote;
   SmallPtrSet<Argument*, 8> ByValArgsToTransform;
   for (unsigned i = 0; i != PointerArgs.size(); ++i) {
     bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
+    Argument *PtrArg = PointerArgs[i].first;
+    const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
 
     // If this is a byval argument, and if the aggregate type is small, just
     // pass the elements, which is always safe.
-    Argument *PtrArg = PointerArgs[i].first;
     if (isByVal) {
-      const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
       if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
         if (maxElements > 0 && STy->getNumElements() > maxElements) {
           DEBUG(dbgs() << "argpromotion disable promoting argument '"
                 << PtrArg->getName() << "' because it would require adding more"
                 << " than " << maxElements << " arguments to the function.\n");
-        } else {
-          // If all the elements are single-value types, we can promote it.
-          bool AllSimple = true;
-          for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
-            if (!STy->getElementType(i)->isSingleValueType()) {
-              AllSimple = false;
-              break;
-            }
-
-          // Safe to transform, don't even bother trying to "promote" it.
-          // Passing the elements as a scalar will allow scalarrepl to hack on
-          // the new alloca we introduce.
-          if (AllSimple) {
-            ByValArgsToTransform.insert(PtrArg);
-            continue;
+          continue;
+        }
+        
+        // If all the elements are single-value types, we can promote it.
+        bool AllSimple = true;
+        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+          if (!STy->getElementType(i)->isSingleValueType()) {
+            AllSimple = false;
+            break;
           }
         }
+
+        // Safe to transform, don't even bother trying to "promote" it.
+        // Passing the elements as a scalar will allow scalarrepl to hack on
+        // the new alloca we introduce.
+        if (AllSimple) {
+          ByValArgsToTransform.insert(PtrArg);
+          continue;
+        }
       }
     }
 
+    // If the argument is a recursive type and we're in a recursive
+    // function, we could end up infinitely peeling the function argument.
+    if (isSelfRecursive) {
+      if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
+        bool RecursiveType = false;
+        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+          if (STy->getElementType(i) == PtrArg->getType()) {
+            RecursiveType = true;
+            break;
+          }
+        }
+        if (RecursiveType)
+          continue;
+      }
+    }
+    
     // Otherwise, see if we can promote the pointer to its value.
     if (isSafeToPromoteArgument(PtrArg, isByVal))
       ArgsToPromote.insert(PtrArg);
@@ -188,9 +215,9 @@ CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
   return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
 }
 
-/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
+/// AllCallersPassInValidPointerForArgument - Return true if we can prove that
 /// all callees pass in a valid pointer for the specified function argument.
-static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
+static bool AllCallersPassInValidPointerForArgument(Argument *Arg) {
   Function *Callee = Arg->getParent();
 
   unsigned ArgNo = std::distance(Callee->arg_begin(),
@@ -310,7 +337,7 @@ bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
   GEPIndicesSet ToPromote;
 
   // If the pointer is always valid, any load with first index 0 is valid.
-  if (isByVal || AllCalleesPassInValidPointerForArgument(Arg))
+  if (isByVal || AllCallersPassInValidPointerForArgument(Arg))
     SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
 
   // First, iterate the entry block and mark loads of (geps of) arguments as
-- 
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