loop-rotate shouldn't hoist alloca instructions out of a loop. Patch by Patrik Hägglund, with slightly modified test. Issue reported by Patrik Hägglund on llvmdev.

llvm-svn: 150642

2 files changed, 35 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 7a60ad20474..59aace9e36d 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -339,7 +339,8 @@ bool LoopRotate::rotateLoop(Loop *L) {
     // memory (without proving that the loop doesn't write).
     if (L->hasLoopInvariantOperands(Inst) &&
         !Inst->mayReadFromMemory() && !Inst->mayWriteToMemory() &&
-        !isa<TerminatorInst>(Inst) && !isa<DbgInfoIntrinsic>(Inst)) {
+        !isa<TerminatorInst>(Inst) && !isa<DbgInfoIntrinsic>(Inst) &&
+        !isa<AllocaInst>(Inst)) {
       Inst->moveBefore(LoopEntryBranch);
       continue;
     }
diff --git a/llvm/test/Transforms/LoopRotate/alloca.ll b/llvm/test/Transforms/LoopRotate/alloca.ll
new file mode 100644
index 00000000000..fd217ea8dcf
--- /dev/null
+++ b/llvm/test/Transforms/LoopRotate/alloca.ll
@@ -0,0 +1,33 @@
+; RUN: opt < %s -loop-rotate -S | FileCheck %s
+
+; Test alloca in -loop-rotate.
+
+; We expect a different value for %ptr each iteration (according to the
+; definition of alloca). I.e. each @use must be paired with an alloca.
+
+; CHECK: call void @use(i8* %
+; CHECK: %ptr = alloca i8
+
+@e = global i16 10
+
+declare void @use(i8*)
+
+define void @test() {
+entry:
+  %end = load i16* @e
+  br label %loop
+
+loop:
+  %n.phi = phi i16 [ %n, %loop.fin ], [ 0, %entry ]
+  %ptr = alloca i8
+  %cond = icmp eq i16 %n.phi, %end
+  br i1 %cond, label %exit, label %loop.fin
+
+loop.fin:
+  %n = add i16 %n.phi, 1
+  call void @use(i8* %ptr)
+  br label %loop
+
+exit:
+  ret void
+}