[RewriteStatepointsForGC] Fix a bug on creating gc_relocate for pointer to vector of pointers

Summary:
In RewriteStatepointsForGC pass, we create a gc_relocate intrinsic for
each relocated pointer, and the gc_relocate has the same type with the
pointer. During the creation of gc_relocate intrinsic, llvm requires to
mangle its type. However, llvm does not support mangling of all possible
types. RewriteStatepointsForGC will hit an assertion failure when it
tries to create a gc_relocate for pointer to vector of pointers because
mangling for vector of pointers is not supported.

This patch changes the way RewriteStatepointsForGC pass creates
gc_relocate. For each relocated pointer, we erase the type of pointers
and create an unified gc_relocate of type i8 addrspace(1)*. Then a
bitcast is inserted to convert the gc_relocate to the correct type. In
this way, gc_relocate does not need to deal with different types of
pointers and the unsupported type mangling is no longer a problem. This
change would also ease further merge when LLVM erases types of pointers
and introduces an unified pointer type.

Some minor changes are also introduced to gc_relocate related part in
InstCombineCalls, CodeGenPrepare, and Verifier accordingly.

Patch by Chen Li!

Reviewers: reames, AndyAyers, sanjoy

Reviewed By: sanjoy

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9592

llvm-svn: 237009

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 374f8f210be..a5d5829b071 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -3384,10 +3384,8 @@ void Verifier::visitIntrinsicFunctionCall(Intrinsic::ID ID, CallInst &CI) {
            "'gc parameters' section of the statepoint call",
            &CI);
 
-    // Assert that the result type matches the type of the relocated pointer
-    GCRelocateOperands Operands(&CI);
-    Assert(Operands.getDerivedPtr()->getType() == CI.getType(),
-           "gc.relocate: relocating a pointer shouldn't change its type", &CI);
+    // gc_relocate does not need to be the same type as the relocated pointer.
+    // It can casted to the correct type later if it's desired
     break;
   }
   };