[JumpThreading] PR36133 enable/disable DominatorTree for LVI analysis

Summary:
The LazyValueInfo pass caches a copy of the DominatorTree when available.
Whenever there are pending DominatorTree updates within JumpThreading's
DeferredDominance object we cannot use the cached DT for LVI analysis.
This commit adds the new methods enableDT() and disableDT() to LVI.
JumpThreading also sets the appropriate usage model before calling LVI
analysis methods.

Fixes https://bugs.llvm.org/show_bug.cgi?id=36133

Reviewers: sebpop, dberlin, kuhar

Reviewed by: sebpop, kuhar

Subscribers: uabelho, llvm-commits, aprantl, hiraditya, a.elovikov

Differential Revision: https://reviews.llvm.org/D42717

llvm-svn: 325356

1 files changed, 44 insertions, 0 deletions

diff --git a/llvm/test/Transforms/JumpThreading/pr36133.ll b/llvm/test/Transforms/JumpThreading/pr36133.ll
new file mode 100644
index 00000000000..b8d8c5fac46
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/pr36133.ll
@@ -0,0 +1,44 @@
+; RUN: opt -jump-threading -S < %s | FileCheck %s
+@global = external global i8*, align 8
+
+define i32 @foo(i32 %arg) {
+; CHECK-LABEL: @foo
+; CHECK-LABEL: bb:
+; CHECK: icmp eq
+; CHECK-NEXT: br i1 %tmp1, label %bb7, label %bb7
+bb:
+  %tmp = load i8*, i8** @global, align 8
+  %tmp1 = icmp eq i8* %tmp, null
+  br i1 %tmp1, label %bb3, label %bb2
+
+; CHECK-NOT: bb2:
+bb2:
+  br label %bb3
+
+; CHECK-NOT: bb3:
+bb3:
+  %tmp4 = phi i8 [ 1, %bb2 ], [ 0, %bb ]
+  %tmp5 = icmp eq i8 %tmp4, 0
+  br i1 %tmp5, label %bb7, label %bb6
+
+; CHECK-NOT: bb6:
+bb6:
+  br label %bb7
+
+; CHECK-LABEL: bb7:
+bb7:
+  %tmp8 = icmp eq i32 %arg, -1
+  br i1 %tmp8, label %bb9, label %bb10
+
+; CHECK-LABEL: bb9:
+bb9:
+  ret i32 0
+
+; CHECK-LABEL: bb10:
+bb10:
+  %tmp11 = icmp sgt i32 %arg, -1
+  call void @llvm.assume(i1 %tmp11)
+  ret i32 1
+}
+
+declare void @llvm.assume(i1)