[llvm-commits] CVS: llvm/lib/Analysis/BasicAliasAnalysis.cpp

[Chris Lattner]

Changes in directory llvm/lib/Analysis:

BasicAliasAnalysis.cpp updated: 1.69 -> 1.70
---
Log message:

By definition, 'tail' calls cannot access the stack frame of their caller.  
Expose this as a simple form of mod/ref information.  This implements
BasicAA/tailcall-modref.ll


---
Diffs of the changes:  (+6 -0)

 BasicAliasAnalysis.cpp |    6 ++++++
 1 files changed, 6 insertions(+)


Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
diff -u llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.69 llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.70
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.69	Fri May  6 00:21:04 2005
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp	Sun May  8 18:58:12 2005
@@ -239,6 +239,12 @@
       // because it simply can't get its address.
       if (!AddressMightEscape(AI))
         return NoModRef;
+
+      // If this is a tail call and P points to a stack location, we know that
+      // the tail call cannot access or modify the local stack.
+      if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
+        if (CI->isTailCall() && isa<AllocaInst>(AI))
+          return NoModRef;
     }
 
   // The AliasAnalysis base class has some smarts, lets use them.