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fix: keep finalizer object field loads in loop under LICM #607
duan创建于 18 天前
fix: keep finalizer object field loads in loop under LICM #607
已开启
共 2 个文件变更+45-0
| @@ -1213,6 +1213,13 @@ bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT, | |||
| 1213 | MemorySSA *MSSA = MSSAU.getMemorySSA(); | 1213 | MemorySSA *MSSA = MSSAU.getMemorySSA(); |
| 1214 | // Loads have extra constraints we have to verify before we can hoist them. | 1214 | // Loads have extra constraints we have to verify before we can hoist them. |
| 1215 | if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { | 1215 | if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { |
| 1216 | + // Avoid moving a read of a finalizer object's field out of the loop. | ||
| 1217 | + // Hoisting/sinking that read removes the only remaining SSA use of the | ||
| 1218 | + // finalizer object inside the loop, so GC liveness reports it dead and | ||
| 1219 | + // the GC collects it while the source program still references it, running | ||
| 1220 | + // its ~init() (finalizer) prematurely. | ||
| 1221 | + if (CJPipeline && maybeCJFinalizerObj(LI->getPointerOperand())) | ||
| 1222 | + return false; | ||
| 1216 | if (!LI->isUnordered()) | 1223 | if (!LI->isUnordered()) |
| 1217 | return false; // Don't sink/hoist volatile or ordered atomic loads! | 1224 | return false; // Don't sink/hoist volatile or ordered atomic loads! |
| 1218 | 1225 | ||
| @@ -0,0 +1,38 @@ | |||
| 1 | +; RUN: opt < %s -licm --cangjie-pipeline -S | FileCheck %s | ||
| 2 | + | ||
| 3 | +; A finalizer object's field load must NOT be hoisted (or sunk) out of a loop. | ||
| 4 | +; Hoisting removes the only SSA use of the finalizer object inside the loop, | ||
| 5 | +; so GC liveness reports it dead and the GC runs its ~init() while the source | ||
| 6 | +; program still references it. | ||
| 7 | + | ||
| 8 | +%KlassInfo.0 = type { [0 x %KlassInfo.0*] } | ||
| 9 | +@_ZN7default1AE.objKlass = weak_odr global %KlassInfo.0 { [0 x %KlassInfo.0*] zeroinitializer } | ||
| 10 | + | ||
| 11 | +declare i8 addrspace(1)* @CJ_MCC_NewFinalizer(i8*, i32) | ||
| 12 | +declare void @use_obj(i8 addrspace(1)*) | ||
| 13 | + | ||
| 14 | +; CHECK-LABEL: define void @finalizer_field_not_hoisted | ||
| 15 | +; The load of the finalizer object field must stay inside the loop body. | ||
| 16 | +; CHECK: br label %loop | ||
| 17 | +; CHECK-NOT: %[[L:.*]] = load i8 addrspace(1)*, i8 addrspace(1)* addrspace(1)* | ||
| 18 | +; CHECK: loop: | ||
| 19 | +; CHECK: %[[L:.*]] = load i8 addrspace(1)*, i8 addrspace(1)* addrspace(1)* | ||
| 20 | +; CHECK: call void @use_obj(i8 addrspace(1)* %[[L]]) | ||
| 21 | +define void @finalizer_field_not_hoisted() gc "cangjie" { | ||
| 22 | +entry: | ||
| 23 | + %0 = call noalias i8 addrspace(1)* @CJ_MCC_NewFinalizer(i8* bitcast (%KlassInfo.0* @_ZN7default1AE.objKlass to i8*), i32 16) | ||
| 24 | + %1 = getelementptr i8, i8 addrspace(1)* %0, i64 8 | ||
| 25 | + %2 = bitcast i8 addrspace(1)* %1 to i8 addrspace(1)* addrspace(1)* | ||
| 26 | + br label %loop | ||
| 27 | + | ||
| 28 | +loop: | ||
| 29 | + %3 = phi i64 [ 0, %entry ], [ %5, %loop ] | ||
| 30 | + %4 = load i8 addrspace(1)*, i8 addrspace(1)* addrspace(1)* %2, align 8 | ||
| 31 | + call void @use_obj(i8 addrspace(1)* %4) | ||
| 32 | + %5 = add i64 %3, 1 | ||
| 33 | + %6 = icmp slt i64 %5, 10 | ||
| 34 | + br i1 %6, label %loop, label %exit | ||
| 35 | + | ||
| 36 | +exit: | ||
| 37 | + ret void | ||
| 38 | +} | ||