[llvm] r213726 - We may visit a call that uses an alloca multiple times in callUsesLocalStack, sometimes with IsNocapture true and sometimes with IsNocapture false. We accidentally skipped work we needed to do in the IsNocapture=false case if we were called with IsNocapture=true the first time. Fixes PR20405!

[Nick Lewycky]

Author: nicholas
Date: Wed Jul 23 01:24:49 2014
New Revision: 213726

URL: http://llvm.org/viewvc/llvm-project?rev=213726&view=rev
Log:
We may visit a call that uses an alloca multiple times in callUsesLocalStack, sometimes with IsNocapture true and sometimes with IsNocapture false. We accidentally skipped work we needed to do in the IsNocapture=false case if we were called with IsNocapture=true the first time. Fixes PR20405!

Modified:
    llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
    llvm/trunk/test/Transforms/TailCallElim/basic.ll

Modified: llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp?rev=213726&r1=213725&r2=213726&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/TailRecursionElimination.cpp Wed Jul 23 01:24:49 2014
@@ -227,12 +227,10 @@ struct AllocaDerivedValueTracker {
   }
 
   void callUsesLocalStack(CallSite CS, bool IsNocapture) {
-    // Add it to the list of alloca users. If it's already there, skip further
-    // processing.
-    if (!AllocaUsers.insert(CS.getInstruction()))
-      return;
+    // Add it to the list of alloca users.
+    AllocaUsers.insert(CS.getInstruction());
 
-    // If it's nocapture then it can't capture the alloca.
+    // If it's nocapture then it can't capture this alloca.
     if (IsNocapture)
       return;
 

Modified: llvm/trunk/test/Transforms/TailCallElim/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/TailCallElim/basic.ll?rev=213726&r1=213725&r2=213726&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/TailCallElim/basic.ll (original)
+++ llvm/trunk/test/Transforms/TailCallElim/basic.ll Wed Jul 23 01:24:49 2014
@@ -174,3 +174,17 @@ if.end:
 return:
   ret void
 }
+
+declare void @test11_helper1(i8** nocapture, i8*)
+declare void @test11_helper2(i8*)
+define void @test11() {
+; CHECK-LABEL: @test11
+; CHECK-NOT: tail
+  %a = alloca i8*
+  %b = alloca i8
+  call void @test11_helper1(i8** %a, i8* %b)  ; a = &b
+  %c = load i8** %a
+  call void @test11_helper2(i8* %c)
+; CHECK: call void @test11_helper2
+  ret void
+}