Don't assume a tail call can't reference a byval

argument to the outer function, this isn't correct.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49731 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 2 deletions

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index b696a80..ad46207 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -273,8 +273,10 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
 
       // 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 (isa<AllocaInst>(Object) ||
-          (isa<Argument>(Object) && cast<Argument>(Object)->hasByValAttr()))
+      // We cannot exclude byval arguments here; these belong to the caller of
+      // the current function not to the current function, and a tail callee
+      // may reference them.
+      if (isa<AllocaInst>(Object))
         if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
           if (CI->isTailCall())
             return NoModRef;
diff --git a/test/Analysis/BasicAA/2008-04-15-Byval.ll b/test/Analysis/BasicAA/2008-04-15-Byval.ll
new file mode 100644
index 0000000..ee16909
--- /dev/null
+++ b/test/Analysis/BasicAA/2008-04-15-Byval.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as < %s | opt -std-compile-opts | llvm-dis | grep store
+; ModuleID = 'small2.c'
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin8"
+	%struct.x = type { [4 x i32] }
+
+define void @foo(%struct.x* byval align 4  %X) nounwind  {
+entry:
+	%tmp = getelementptr %struct.x* %X, i32 0, i32 0		; <[4 x i32]*> [#uses=1]
+	%tmp1 = getelementptr [4 x i32]* %tmp, i32 0, i32 3		; <i32*> [#uses=1]
+	store i32 2, i32* %tmp1, align 4
+	%tmp2 = call i32 (...)* @bar( %struct.x* byval align 4  %X ) nounwind 		; <i32> [#uses=0]
+	br label %return
+return:		; preds = %entry
+	ret void
+}
+
+declare i32 @bar(...)