Memory Dependence Analysis: fix a miscompile that uses DT to approxmiate the

reachablity.

We conservatively approximate the reachability analysis by saying it is not
reachable if there is a single path starting from "From" and the path does not
reach "To".

rdar://12801584


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171512 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 54 insertions, 0 deletions

diff --git a/test/Transforms/GVN/MemdepMiscompile.ll b/test/Transforms/GVN/MemdepMiscompile.ll
new file mode 100644
index 0000000..d420169
--- /dev/null
+++ b/test/Transforms/GVN/MemdepMiscompile.ll
@@ -0,0 +1,54 @@
+; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-macosx10.7.0"
+
+; rdar://12801584
+; Value of %shouldExit can be changed by RunInMode.
+; Make sure we do not replace load %shouldExit in while.cond.backedge
+; with a phi node where the value from while.body is 0.
+define i32 @test() nounwind ssp {
+entry:
+; CHECK: test()
+; CHECK: while.body:
+; CHECK: call void @RunInMode
+; CHECK: br i1 %tobool, label %while.cond.backedge, label %if.then
+; CHECK: while.cond.backedge:
+; CHECK: load i32* %shouldExit
+; CHECK: br i1 %cmp, label %while.body
+  %shouldExit = alloca i32, align 4
+  %tasksIdle = alloca i32, align 4
+  store i32 0, i32* %shouldExit, align 4
+  store i32 0, i32* %tasksIdle, align 4
+  call void @CTestInitialize(i32* %tasksIdle) nounwind
+  %0 = load i32* %shouldExit, align 4
+  %cmp1 = icmp eq i32 %0, 0
+  br i1 %cmp1, label %while.body.lr.ph, label %while.end
+
+while.body.lr.ph:
+  br label %while.body
+
+while.body:
+  call void @RunInMode(i32 100) nounwind
+  %1 = load i32* %tasksIdle, align 4
+  %tobool = icmp eq i32 %1, 0
+  br i1 %tobool, label %while.cond.backedge, label %if.then
+
+if.then:
+  store i32 0, i32* %tasksIdle, align 4
+  call void @TimerCreate(i32* %shouldExit) nounwind
+  br label %while.cond.backedge
+
+while.cond.backedge:
+  %2 = load i32* %shouldExit, align 4
+  %cmp = icmp eq i32 %2, 0
+  br i1 %cmp, label %while.body, label %while.cond.while.end_crit_edge
+
+while.cond.while.end_crit_edge:
+  br label %while.end
+
+while.end:
+  ret i32 0
+}
+declare void @CTestInitialize(i32*)
+declare void @RunInMode(i32)
+declare void @TimerCreate(i32*)