Don't ignore memcpy in GC root placement

tpapp · Sep 2, 2017 · 3c68dcd · 3c68dcd
1 parent 92ff781
commit 3c68dcd
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Showing 2 changed files with 31 additions and 3 deletions.
diff --git a/src/llvm-late-gc-lowering.cpp b/src/llvm-late-gc-lowering.cpp
@@ -728,8 +728,16 @@ State LateLowerGCFrame::LocalScan(Function &F) {
  Instruction &I = *it;
  if (CallInst *CI = dyn_cast<CallInst>(&I)) {
  if (isa<IntrinsicInst>(CI)) {
- // Intrinsics are never GC uses/defs
- continue;
+ // Most intrinsics are not gc uses/defs, however some have
+ // memory operands and could thus be GC uses. To be conservative,
+ // we only skip processing for those that we know we emit often
+ // and cannot possibly be GC uses.
+ IntrinsicInst *II = cast<IntrinsicInst>(CI);
+ if (isa<DbgInfoIntrinsic>(CI) ||
+ II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end) {
+ continue;
+ }
  }
  MaybeNoteDef(S, BBS, CI, BBS.Safepoints);
  NoteOperandUses(S, BBS, I, BBS.UpExposedUses);
@@ -743,6 +751,10 @@ State LateLowerGCFrame::LocalScan(Function &F) {
  if (CI->canReturnTwice()) {
  S.ReturnsTwice.push_back(CI);
  }
+ if (isa<IntrinsicInst>(CI)) {
+ // Intrinsics are never safepoints.
+ continue;
+ }
  if (auto callee = CI->getCalledFunction()) {
  // Known functions emitted in codegen that are not safepoints
  if (callee == pointer_from_objref_func || callee->getName() == "memcmp") {

diff --git a/test/llvmpasses/gcroots.ll b/test/llvmpasses/gcroots.ll
@@ -192,7 +192,7 @@ define %jl_value_t addrspace(10)* @no_redundant_rerooting(i64 %a, i1 %cond) {
 top:
  %ptls = call %jl_value_t*** @jl_get_ptls_states()
  %aboxed = call %jl_value_t addrspace(10)* @jl_box_int64(i64 signext %a)
-; CHECK: store %jl_value_t addrspace(10)* %aboxed 
+; CHECK: store %jl_value_t addrspace(10)* %aboxed
 ; CHECK-NEXT: call void @jl_safepoint()
  call void @jl_safepoint()
  br i1 %cond, label %blocka, label %blockb
@@ -207,3 +207,19 @@ blockb:
  call void @jl_safepoint()
  ret %jl_value_t addrspace(10)* %aboxed
 }
+
+declare void @llvm.memcpy.p064.p10i8.i64(i64*, i8 addrspace(10)*, i64, i32, i1)
+
+define void @memcpy_use(i64 %a, i64 *%aptr) {
+; CHECK-LABEL: @memcpy_use
+; CHECK: %gcframe = alloca %jl_value_t addrspace(10)*, i32 3
+top:
+ %ptls = call %jl_value_t*** @jl_get_ptls_states()
+ %aboxed = call %jl_value_t addrspace(10)* @jl_box_int64(i64 signext %a)
+; CHECK: store %jl_value_t addrspace(10)* %aboxed
+ call void @jl_safepoint()
+ %acast = bitcast %jl_value_t addrspace(10)* %aboxed to i8 addrspace(10)*
+ call void @llvm.memcpy.p064.p10i8.i64(i64* %aptr, i8 addrspace(10)* %acast, i64 8, i32 1, i1 false)
+ ret void
+}
+