[X86] If PreprocessISelDAG reorders a load before a call, make sure we remove dead...

The reordering can leave at least a dead TokenFactor in the graph. This cause the linearize scheduler to fail with something like the assert seen in PR22614. This is only one of many ways we can break the linearize scheduler today so I can't say for sure that any of the other failures in that bug were caused by this issue.

This takes the heavy hammer approach of just running RemoveDeadNodes unconditionally at the end of the PreprocessISelDAG. If this turns out to be a compile time hit, we can try to refine it.

Differential Revision: https://reviews.llvm.org/D61164

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359582 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index c16fbe03ec5ed74cc44d9b99df5070af4c249956..450872d8619578deeb2b08154b7f3650935090d0 100644 (file)
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -907,6 +907,11 @@ void X86DAGToDAGISel::PreprocessISelDAG() {
     ++I;
     CurDAG->DeleteNode(N);
   }
+
+  // The load+call transform above can leave some dead nodes in the graph. Make
+  // sure we remove them. Its possible some of the other transforms do to so
+  // just remove dead nodes unconditionally.
+  CurDAG->RemoveDeadNodes();
 }
 
 // Look for a redundant movzx/movsx that can occur after an 8-bit divrem.

diff --git a/test/CodeGen/X86/fold-call-3.ll b/test/CodeGen/X86/fold-call-3.ll
index e7e81b9422a1438df63f08649a94071f73fd2a6b..840a32447f1c83a656a0123e5bc64f4c6ab996d7 100644 (file)
--- a/test/CodeGen/X86/fold-call-3.ll
+++ b/test/CodeGen/X86/fold-call-3.ll
@@ -1,5 +1,7 @@
 ; RUN: llc < %s -mtriple=x86_64-apple-darwin | grep call | grep 560
 ; rdar://6522427
+; This command line used to crash due to dangling nodes left after PreprocessISelDAG
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -pre-RA-sched=linearize
 
        %"struct.clang::Action" = type { %"struct.clang::ActionBase" }
        %"struct.clang::ActionBase" = type { i32 (...)** }