diff --git a/transform/gc.go b/transform/gc.go index 57c53830..27300bad 100644 --- a/transform/gc.go +++ b/transform/gc.go @@ -150,11 +150,14 @@ func MakeGCStackSlots(mod llvm.Module) bool { continue } switch ptr.InstructionOpcode() { - case llvm.PHI, llvm.GetElementPtr: + case llvm.GetElementPtr: // These values do not create new values: the values already // existed locally in this function so must have been tracked // already. continue + case llvm.PHI: + // While the value may have already been tracked, it may be overwritten in a loop. + // Therefore, a second copy must be created to ensure that it is tracked over the entirety of its lifetime. case llvm.ExtractValue, llvm.BitCast: // These instructions do not create new values, but their // original value may not be tracked. So keep tracking them for @@ -228,11 +231,22 @@ func MakeGCStackSlots(mod llvm.Module) bool { // Do a store to the stack object after each new pointer that is created. for i, ptr := range pointers { - builder.SetInsertPointBefore(llvm.NextInstruction(ptr)) + // Insert the store after the pointer value is created. + insertionPoint := llvm.NextInstruction(ptr) + for !insertionPoint.IsAPHINode().IsNil() { + // PHI nodes are required to be at the start of the block. + // Insert after the last PHI node. + insertionPoint = llvm.NextInstruction(insertionPoint) + } + builder.SetInsertPointBefore(insertionPoint) + + // Extract a pointer to the appropriate section of the stack object. gep := builder.CreateGEP(stackObject, []llvm.Value{ llvm.ConstInt(ctx.Int32Type(), 0, false), llvm.ConstInt(ctx.Int32Type(), uint64(2+len(allocas)+i), false), }, "") + + // Store the pointer into the stack slot. builder.CreateStore(ptr, gep) } diff --git a/transform/testdata/gc-stackslots.ll b/transform/testdata/gc-stackslots.ll index 5e62f8c5..10d10975 100644 --- a/transform/testdata/gc-stackslots.ll +++ b/transform/testdata/gc-stackslots.ll @@ -50,3 +50,37 @@ define i8* @noAllocatingFunction() { call void @runtime.trackPointer(i8* %ptr) ret i8* %ptr } + +define i8* @fibNext(i8* %x, i8* %y) { + %x.val = load i8, i8* %x + %y.val = load i8, i8* %y + %out.val = add i8 %x.val, %y.val + %out.alloc = call i8* @runtime.alloc(i32 1) + call void @runtime.trackPointer(i8* %out.alloc) + store i8 %out.val, i8* %out.alloc + ret i8* %out.alloc +} + +define i8* @allocLoop() { +entry: + %entry.x = call i8* @runtime.alloc(i32 1) + call void @runtime.trackPointer(i8* %entry.x) + %entry.y = call i8* @runtime.alloc(i32 1) + call void @runtime.trackPointer(i8* %entry.y) + store i8 1, i8* %entry.y + br label %loop + +loop: + %prev.y = phi i8* [ %entry.y, %entry ], [ %prev.x, %loop ] + %prev.x = phi i8* [ %entry.x, %entry ], [ %next.x, %loop ] + call void @runtime.trackPointer(i8* %prev.x) + call void @runtime.trackPointer(i8* %prev.y) + %next.x = call i8* @fibNext(i8* %prev.x, i8* %prev.y) + call void @runtime.trackPointer(i8* %next.x) + %next.x.val = load i8, i8* %next.x + %loop.done = icmp ult i8 40, %next.x.val + br i1 %loop.done, label %end, label %loop + +end: + ret i8* %next.x +} diff --git a/transform/testdata/gc-stackslots.out.ll b/transform/testdata/gc-stackslots.out.ll index aa0aa35a..c24793ea 100644 --- a/transform/testdata/gc-stackslots.out.ll +++ b/transform/testdata/gc-stackslots.out.ll @@ -56,3 +56,59 @@ define i8* @noAllocatingFunction() { %ptr = call i8* @getPointer() ret i8* %ptr } + +define i8* @fibNext(i8* %x, i8* %y) { + %gc.stackobject = alloca { %runtime.stackChainObject*, i32, i8* } + store { %runtime.stackChainObject*, i32, i8* } { %runtime.stackChainObject* null, i32 1, i8* null }, { %runtime.stackChainObject*, i32, i8* }* %gc.stackobject + %1 = load %runtime.stackChainObject*, %runtime.stackChainObject** @runtime.stackChainStart + %2 = getelementptr { %runtime.stackChainObject*, i32, i8* }, { %runtime.stackChainObject*, i32, i8* }* %gc.stackobject, i32 0, i32 0 + store %runtime.stackChainObject* %1, %runtime.stackChainObject** %2 + %3 = bitcast { %runtime.stackChainObject*, i32, i8* }* %gc.stackobject to %runtime.stackChainObject* + store %runtime.stackChainObject* %3, %runtime.stackChainObject** @runtime.stackChainStart + %x.val = load i8, i8* %x + %y.val = load i8, i8* %y + %out.val = add i8 %x.val, %y.val + %out.alloc = call i8* @runtime.alloc(i32 1) + %4 = getelementptr { %runtime.stackChainObject*, i32, i8* }, { %runtime.stackChainObject*, i32, i8* }* %gc.stackobject, i32 0, i32 2 + store i8* %out.alloc, i8** %4 + store i8 %out.val, i8* %out.alloc + store %runtime.stackChainObject* %1, %runtime.stackChainObject** @runtime.stackChainStart + ret i8* %out.alloc +} + +define i8* @allocLoop() { +entry: + %gc.stackobject = alloca { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* } + store { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* } { %runtime.stackChainObject* null, i32 5, i8* null, i8* null, i8* null, i8* null, i8* null }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject + %0 = load %runtime.stackChainObject*, %runtime.stackChainObject** @runtime.stackChainStart + %1 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 0 + store %runtime.stackChainObject* %0, %runtime.stackChainObject** %1 + %2 = bitcast { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject to %runtime.stackChainObject* + store %runtime.stackChainObject* %2, %runtime.stackChainObject** @runtime.stackChainStart + %entry.x = call i8* @runtime.alloc(i32 1) + %3 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 2 + store i8* %entry.x, i8** %3 + %entry.y = call i8* @runtime.alloc(i32 1) + %4 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 3 + store i8* %entry.y, i8** %4 + store i8 1, i8* %entry.y + br label %loop + +loop: + %prev.y = phi i8* [ %entry.y, %entry ], [ %prev.x, %loop ] + %prev.x = phi i8* [ %entry.x, %entry ], [ %next.x, %loop ] + %5 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 5 + store i8* %prev.y, i8** %5 + %6 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 4 + store i8* %prev.x, i8** %6 + %next.x = call i8* @fibNext(i8* %prev.x, i8* %prev.y) + %7 = getelementptr { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }, { %runtime.stackChainObject*, i32, i8*, i8*, i8*, i8*, i8* }* %gc.stackobject, i32 0, i32 6 + store i8* %next.x, i8** %7 + %next.x.val = load i8, i8* %next.x + %loop.done = icmp ult i8 40, %next.x.val + br i1 %loop.done, label %end, label %loop + +end: + store %runtime.stackChainObject* %0, %runtime.stackChainObject** @runtime.stackChainStart + ret i8* %next.x +}