[llvm] a40af85 - [RS4GC] Handle special cases in unreachable code for memcpy/memmov

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2022-07-22T11:30:43+07:00
New Revision: a40af8589e88f7ebaf81d11a9aa5a4eaf1735eff

URL: https://github.com/llvm/llvm-project/commit/a40af8589e88f7ebaf81d11a9aa5a4eaf1735eff
DIFF: https://github.com/llvm/llvm-project/commit/a40af8589e88f7ebaf81d11a9aa5a4eaf1735eff.diff

LOG: [RS4GC] Handle special cases in unreachable code for memcpy/memmov

The existing code doesn't expect dummy values (undef, poison, null-derived
constants etc) as arguments of these intrinsics. However, they can be there
in unreached code. Currently we fail trying to find base for them.

Handle these cases separately. Return null as base for them to be consistent
with the handling in the main algorithm in findBaseDefiningValue.

Differential Revision: https://reviews.llvm.org/D129561
Reviewed By: apilipenko

Added: 
    llvm/test/Transforms/RewriteStatepointsForGC/pr56493.ll

Modified: 
    llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index 51e4a5773f3ee..baf407c5037bf 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -1702,10 +1702,20 @@ makeStatepointExplicitImpl(CallBase *Call, /* to replace */
       auto &Context = Call->getContext();
       auto &DL = Call->getModule()->getDataLayout();
       auto GetBaseAndOffset = [&](Value *Derived) {
-        assert(PointerToBase.count(Derived));
+        Value *Base = nullptr;
+        // Optimizations in unreachable code might substitute the real pointer
+        // with undef, poison or null-derived constant. Return null base for
+        // them to be consistent with the handling in the main algorithm in
+        // findBaseDefiningValue.
+        if (isa<Constant>(Derived))
+          Base =
+              ConstantPointerNull::get(cast<PointerType>(Derived->getType()));
+        else {
+          assert(PointerToBase.count(Derived));
+          Base = PointerToBase.find(Derived)->second;
+        }
         unsigned AddressSpace = Derived->getType()->getPointerAddressSpace();
         unsigned IntPtrSize = DL.getPointerSizeInBits(AddressSpace);
-        Value *Base = PointerToBase.find(Derived)->second;
         Value *Base_int = Builder.CreatePtrToInt(
             Base, Type::getIntNTy(Context, IntPtrSize));
         Value *Derived_int = Builder.CreatePtrToInt(

diff  --git a/llvm/test/Transforms/RewriteStatepointsForGC/pr56493.ll b/llvm/test/Transforms/RewriteStatepointsForGC/pr56493.ll
new file mode 100644
index 0000000000000..84937af65ee69
--- /dev/null
+++ b/llvm/test/Transforms/RewriteStatepointsForGC/pr56493.ll
@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=rewrite-statepoints-for-gc -S < %s | FileCheck %s
+
+; Make sure this doesn't crash.
+define void @test() gc "statepoint-example" personality i32* ()* @zot {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[STATEPOINT_TOKEN:%.*]] = call token (i64, i32, void (i32 addrspace(1)*, i64, i32 addrspace(1)*, i64, i64)*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidp1i32i64p1i32i64i64f(i64 2882400000, i32 0, void (i32 addrspace(1)*, i64, i32 addrspace(1)*, i64, i64)* elementtype(void (i32 addrspace(1)*, i64, i32 addrspace(1)*, i64, i64)) @__llvm_memcpy_element_unordered_atomic_safepoint_4, i32 5, i32 0, i32 addrspace(1)* null, i64 undef, i32 addrspace(1)* null, i64 ptrtoint (i8 addrspace(1)* getelementptr inbounds (i8, i8 addrspace(1)* null, i64 16) to i64), i64 undef, i32 0, i32 0) [ "deopt"() ]
+; CHECK-NEXT:    ret void
+;
+bb:
+  call void @llvm.memcpy.element.unordered.atomic.p1i32.p1i32.i64(i32 addrspace(1)* elementtype(i32) align 8 undef, i32 addrspace(1)* elementtype(i32) align 16 bitcast (i8 addrspace(1)* getelementptr inbounds (i8, i8 addrspace(1)* null, i64 16) to i32 addrspace(1)*), i64 undef, i32 4) #3 [ "deopt"() ]
+  ret void
+}
+
+declare i32* @zot()
+
+declare void @llvm.memcpy.element.unordered.atomic.p1i32.p1i32.i64(i32 addrspace(1)* nocapture writeonly, i32 addrspace(1)* nocapture readonly, i64, i32 immarg)