Change CaptureTracking to pass a Use* instead of a Value* when a value is

captured. This allows the tracker to look at the specific use, which may be
especially interesting for function calls.

Use this to fix 'nocapture' deduction in FunctionAttrs. The existing one does
not iterate until a fixpoint and does not guarantee that it produces the same
result regardless of iteration order. The new implementation builds up a graph
of how arguments are passed from function to function, and uses a bottom-up walk
on the argument-SCCs to assign nocapture. This gets us nocapture more often, and
does so rather efficiently and independent of iteration order.

llvm-svn: 147327

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
index 704e27b5ce6..53d666078ed 100644
--- a/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -349,7 +349,8 @@ namespace {
       return true;
     }
 
-    bool captured(Instruction *I) {
+    bool captured(Use *U) {
+      Instruction *I = cast<Instruction>(U->getUser());
       if (BeforeHere != I && DT->dominates(BeforeHere, I))
         return false;
       Captured = true;