[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
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 4983625..6413161 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -600,13 +600,51 @@
// Create a Builder and replace the target callsite with a gep
IRBuilder<> Builder(ToReplace);
Builder.SetCurrentDebugLocation(ToReplace->getDebugLoc());
+
+ // If gc_relocate does not match the actual type, cast it to the right type.
+ // In theory, there must be a bitcast after gc_relocate if the type does not
+ // match, and we should reuse it to get the derived pointer. But it could be
+ // cases like this:
+ // bb1:
+ // ...
+ // %g1 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
+ // br label %merge
+ //
+ // bb2:
+ // ...
+ // %g2 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
+ // br label %merge
+ //
+ // merge:
+ // %p1 = phi i8 addrspace(1)* [ %g1, %bb1 ], [ %g2, %bb2 ]
+ // %cast = bitcast i8 addrspace(1)* %p1 in to i32 addrspace(1)*
+ //
+ // In this case, we can not find the bitcast any more. So we insert a new bitcast
+ // no matter there is already one or not. In this way, we can handle all cases, and
+ // the extra bitcast should be optimized away in later passes.
+ Instruction *ActualRelocatedBase = RelocatedBase;
+ if (RelocatedBase->getType() != Base->getType()) {
+ ActualRelocatedBase =
+ cast<Instruction>(Builder.CreateBitCast(RelocatedBase, Base->getType()));
+ ActualRelocatedBase->removeFromParent();
+ ActualRelocatedBase->insertAfter(cast<Instruction>(RelocatedBase));
+ }
Value *Replacement = Builder.CreateGEP(
- Derived->getSourceElementType(), RelocatedBase, makeArrayRef(OffsetV));
+ Derived->getSourceElementType(), ActualRelocatedBase, makeArrayRef(OffsetV));
Instruction *ReplacementInst = cast<Instruction>(Replacement);
ReplacementInst->removeFromParent();
- ReplacementInst->insertAfter(RelocatedBase);
+ ReplacementInst->insertAfter(ActualRelocatedBase);
Replacement->takeName(ToReplace);
- ToReplace->replaceAllUsesWith(Replacement);
+ // If the newly generated derived pointer's type does not match the original derived
+ // pointer's type, cast the new derived pointer to match it. Same reasoning as above.
+ Instruction *ActualReplacement = ReplacementInst;
+ if (ReplacementInst->getType() != ToReplace->getType()) {
+ ActualReplacement =
+ cast<Instruction>(Builder.CreateBitCast(ReplacementInst, ToReplace->getType()));
+ ActualReplacement->removeFromParent();
+ ActualReplacement->insertAfter(ReplacementInst);
+ }
+ ToReplace->replaceAllUsesWith(ActualReplacement);
ToReplace->eraseFromParent();
MadeChange = true;