Fix a scalability issue with complex ConstantExprs.

This is basically the same fix in three different places. We use a set to avoid
walking the whole tree of a big ConstantExprs multiple times.

For example: (select cmp, (add big_expr 1), (add big_expr 2))
We don't want to visit big_expr twice here, it may consist of thousands of
nodes.

The testcase exercises this by creating an insanely large ConstantExprs out of
a loop. It's questionable if the optimizer should ever create those, but this
can be triggered with real C code. Fixes PR15714.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179458 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 97 insertions, 0 deletions

diff --git a/test/Transforms/GlobalDCE/complex-constantexpr.ll b/test/Transforms/GlobalDCE/complex-constantexpr.ll
new file mode 100644
index 0000000..4bf1aee
--- /dev/null
+++ b/test/Transforms/GlobalDCE/complex-constantexpr.ll
@@ -0,0 +1,97 @@
+; RUN: opt -O2 -disable-output < %s
+; PR15714
+
+%struct.ham = type { i32 }
+
+@global5 = common global i32 0, align 4
+@global6 = common global i32 0, align 4
+@global7 = common global i32 0, align 4
+@global = common global i32 0, align 4
+@global8 = common global %struct.ham zeroinitializer, align 4
+@global9 = common global i32 0, align 4
+@global10 = common global i32 0, align 4
+@global11 = common global i32 0, align 4
+
+define void @zot12() {
+bb:
+  store i32 0, i32* @global5, align 4
+  store i32 0, i32* @global6, align 4
+  br label %bb2
+
+bb1:                                              ; preds = %bb11
+  %tmp = load i32* @global5, align 4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %tmp3 = phi i32 [ %tmp, %bb1 ], [ 0, %bb ]
+  %tmp4 = xor i32 %tmp3, zext (i1 icmp ne (i64 ptrtoint (i32* @global5 to i64), i64 1) to i32)
+  store i32 %tmp4, i32* @global5, align 4
+  %tmp5 = icmp eq i32 %tmp3, zext (i1 icmp ne (i64 ptrtoint (i32* @global5 to i64), i64 1) to i32)
+  br i1 %tmp5, label %bb8, label %bb6
+
+bb6:                                              ; preds = %bb2
+  %tmp7 = tail call i32 @quux13()
+  br label %bb8
+
+bb8:                                              ; preds = %bb6, %bb2
+  %tmp9 = load i32* @global7, align 4
+  %tmp10 = icmp eq i32 %tmp9, 0
+  br i1 %tmp10, label %bb11, label %bb15
+
+bb11:                                             ; preds = %bb8
+  %tmp12 = load i32* @global6, align 4
+  %tmp13 = add nsw i32 %tmp12, 1
+  store i32 %tmp13, i32* @global6, align 4
+  %tmp14 = icmp slt i32 %tmp13, 42
+  br i1 %tmp14, label %bb1, label %bb15
+
+bb15:                                             ; preds = %bb11, %bb8
+  ret void
+}
+
+define i32 @quux13() {
+bb:
+  store i32 1, i32* @global5, align 4
+  ret i32 1
+}
+
+define void @wombat() {
+bb:
+  tail call void @zot12()
+  ret void
+}
+
+define void @wombat14() {
+bb:
+  tail call void @blam()
+  ret void
+}
+
+define void @blam() {
+bb:
+  store i32 ptrtoint (i32* @global to i32), i32* getelementptr inbounds (%struct.ham* @global8, i64 0, i32 0), align 4
+  store i32 0, i32* @global9, align 4
+  %tmp = load i32* getelementptr inbounds (%struct.ham* @global8, i64 0, i32 0), align 4
+  br label %bb1
+
+bb1:                                              ; preds = %bb1, %bb
+  %tmp2 = phi i32 [ 0, %bb ], [ %tmp11, %bb1 ]
+  %tmp3 = phi i32 [ %tmp, %bb ], [ %tmp10, %bb1 ]
+  %tmp4 = icmp sgt i32 %tmp3, 0
+  %tmp5 = zext i1 %tmp4 to i32
+  %tmp6 = urem i32 %tmp5, 5
+  %tmp7 = mul i32 %tmp3, -80
+  %tmp8 = or i32 %tmp7, %tmp6
+  %tmp9 = icmp eq i32 %tmp8, 0
+  %tmp10 = zext i1 %tmp9 to i32
+  %tmp11 = add nsw i32 %tmp2, 1
+  %tmp12 = icmp eq i32 %tmp11, 20
+  br i1 %tmp12, label %bb13, label %bb1
+
+bb13:                                             ; preds = %bb1
+  store i32 %tmp10, i32* getelementptr inbounds (%struct.ham* @global8, i64 0, i32 0), align 4
+  store i32 0, i32* @global10, align 4
+  store i32 %tmp6, i32* @global11, align 4
+  store i32 20, i32* @global9, align 4
+  ret void
+}