[RewriteStatepoints] Fix stale parse points

Summary:
RewriteStatepointsForGC collects parse points for further processing.
During the collection if a callsite is found in an unreachable block
(DominatorTree::isReachableFromEntry()) then all unreachable blocks are
removed by removeUnreachableBlocks(). Some of the removed blocks could
have been reachable according to DominatorTree::isReachableFromEntry().
In this case the collected parse points became stale and resulted in a
crash when accessed.

The fix is to unconditionally canonicalize the IR to
removeUnreachableBlocks and then collect the parse points.

The added test crashes with the old version and passes with this patch.

Patch by Yevgeny Rouban!

Reviewed by: Anna

Differential Revision: https://reviews.llvm.org/D43929

llvm-svn: 326748

1 files changed, 34 insertions, 0 deletions

diff --git a/llvm/test/Transforms/RewriteStatepointsForGC/unreachable-regression.ll b/llvm/test/Transforms/RewriteStatepointsForGC/unreachable-regression.ll
new file mode 100644
index 00000000000..1f781a4ce19
--- /dev/null
+++ b/llvm/test/Transforms/RewriteStatepointsForGC/unreachable-regression.ll
@@ -0,0 +1,34 @@
+; RUN: opt -S -rewrite-statepoints-for-gc < %s | FileCheck %s
+; RUN: opt -S -passes=rewrite-statepoints-for-gc < %s | FileCheck %s
+;
+; Regression test:
+;   After the rewritable callsite collection if any callsite was found
+;   in a block that was reported unreachable by DominanceTree then
+;   removeUnreachableBlocks() was called. But it is stronger than
+;   DominatorTree::isReachableFromEntry(), i.e. removeUnreachableBlocks
+;   can remove some blocks for which isReachableFromEntry() returns true.
+;   This resulted in stale pointers to the collected but removed
+;   callsites. Such stale pointers caused crash when accessed.
+declare void @f(i8 addrspace(1)* %obj)
+
+define void @test(i8 addrspace(1)* %arg) gc "statepoint-example" {
+; CHECK-LABEL: test(
+; CHECK-NEXT: @f
+ call void @f(i8 addrspace(1)* %arg) #1
+ br i1 true, label %not_zero, label %zero
+
+not_zero:
+ ret void
+
+; This block is reachable but removed by removeUnreachableBlocks()
+zero:
+; CHECK-NOT: @f
+ call void @f(i8 addrspace(1)* %arg) #1
+ ret void
+
+unreach:
+ call void @f(i8 addrspace(1)* %arg) #1
+ ret void
+}
+
+attributes #1 = { norecurse noimplicitfloat }