1 files changed, 35 insertions, 1 deletions
diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index 1f7625d..9590df9 100644
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -19,6 +19,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/InlineCost.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Transforms/IPO/InlinerPass.h"
 #include "llvm/Transforms/Utils/Cloning.h"
@@ -327,6 +328,37 @@ static bool InlineHistoryIncludes(Function *F, int InlineHistoryID,
   return false;
 }
 
+/// \brief Simplify arguments going into a particular callsite.
+///
+/// This is important to do each time we add a callsite due to inlining so that
+/// constants and other entities which feed into inline cost estimation are
+/// properly recognized when analyzing the new callsite. Consider:
+///   void outer(int x) {
+///     if (x < 42)
+///       return inner(42 - x);
+///     ...
+///   }
+///   void inner(int x) {
+///     ...
+///   }
+///
+/// The inliner gives calls to 'outer' with a constant argument a bonus because
+/// it will delete one side of a branch. But the resulting call to 'inner'
+/// will, after inlining, also have a constant operand. We need to do just
+/// enough constant folding to expose this for callsite arguments. The rest
+/// will be taken care of after the inliner finishes running.
+static void simplifyCallSiteArguments(const TargetData *TD, CallSite CS) {
+  // FIXME: It would be nice to avoid this smallvector if RAUW doesn't
+  // invalidate operand iterators in any cases.
+  SmallVector<std::pair<Value *, Value*>, 4> SimplifiedArgs;
+  for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+       I != E; ++I)
+    if (Instruction *Inst = dyn_cast<Instruction>(*I))
+      if (Value *SimpleArg = SimplifyInstruction(Inst, TD))
+        SimplifiedArgs.push_back(std::make_pair(Inst, SimpleArg));
+  for (unsigned Idx = 0, Size = SimplifiedArgs.size(); Idx != Size; ++Idx)
+    SimplifiedArgs[Idx].first->replaceAllUsesWith(SimplifiedArgs[Idx].second);
+}
 
 bool Inliner::runOnSCC(CallGraphSCC &SCC) {
   CallGraph &CG = getAnalysis<CallGraph>();
@@ -455,7 +487,9 @@ bool Inliner::runOnSCC(CallGraphSCC &SCC) {
           for (unsigned i = 0, e = InlineInfo.InlinedCalls.size();
                i != e; ++i) {
             Value *Ptr = InlineInfo.InlinedCalls[i];
-            CallSites.push_back(std::make_pair(CallSite(Ptr), NewHistoryID));
+            CallSite NewCS = Ptr;
+            simplifyCallSiteArguments(TD, NewCS);
+            CallSites.push_back(std::make_pair(NewCS, NewHistoryID));
           }
         }