[FaultMaps] Let the frontend pre-select implicit null check candidates.
Summary:
This change introduces a !make.implicit metadata that allows the
frontend to pre-select the set of explicit null checks that will be
considered for transformation into implicit null checks.
The reason for not using profiling data instead of !make.implicit is
explained in the change to `FaultMaps.rst`.
Reviewers: atrick, reames, pgavlin, JosephTremoulet
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D10824
llvm-svn: 241116
diff --git a/llvm/lib/CodeGen/ImplicitNullChecks.cpp b/llvm/lib/CodeGen/ImplicitNullChecks.cpp
index d7644a6..a02cd67 100644
--- a/llvm/lib/CodeGen/ImplicitNullChecks.cpp
+++ b/llvm/lib/CodeGen/ImplicitNullChecks.cpp
@@ -124,6 +124,13 @@
MachineBasicBlock &MBB, SmallVectorImpl<NullCheck> &NullCheckList) {
typedef TargetInstrInfo::MachineBranchPredicate MachineBranchPredicate;
+ MDNode *BranchMD =
+ MBB.getBasicBlock()
+ ? MBB.getBasicBlock()->getTerminator()->getMetadata("make.implicit")
+ : nullptr;
+ if (!BranchMD)
+ return false;
+
MachineBranchPredicate MBP;
if (TII->AnalyzeBranchPredicate(MBB, MBP, true))