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By definition, 'tail' calls cannot access the stack frame of their caller.

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Expose this as a simple form of mod/ref information.  This implements
BasicAA/tailcall-modref.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21796 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2005-05-08 23:58:12 +00:00
parent 20fad44ede
commit 42e3c81c5f
1 changed files with 6 additions and 0 deletions
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6
lib/Analysis/BasicAliasAnalysis.cpp
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@ -239,6 +239,12 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
// because it simply can't get its address. // because it simply can't get its address.
if (!AddressMightEscape(AI)) if (!AddressMightEscape(AI))
return NoModRef; 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. // The AliasAnalysis base class has some smarts, lets use them.