c41a212712
I found that when I enable ThinLTO, a miscompilation triggers that had
been hidden all the time previously. The bug appears to happen as
follows:
1. TinyGo generates a function with a runtime.trackPointer call, but
without an alloca (or the alloca gets optimized away).
2. LLVM sees that no alloca needs to be kept alive across the
runtime.trackPointer call, and therefore it adds the 'tail' flag.
One of the effects of this flag is that it makes it undefined
behavior to keep allocas alive across the call (which is still safe
at that point).
3. The GC lowering pass adds a stack slot alloca and converts
runtime.trackPointer calls into alloca stores.
The last step triggers the bug: the compiler inserts an alloca where
there was none before but that's not valid as long as the 'tail' flag is
present.
This patch fixes the bug in a somewhat dirty way, by always creating a
dummy alloca so that LLVM won't do the optimization in step 2 (and
possibly other optimizations that rely on there being no alloca
instruction).
115 строки
5,4 КиБ
LLVM
115 строки
5,4 КиБ
LLVM
; ModuleID = 'channel.go'
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source_filename = "channel.go"
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target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20"
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target triple = "wasm32-unknown-wasi"
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%runtime.channelBlockedList = type { ptr, ptr, ptr, { ptr, i32, i32 } }
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%runtime.chanSelectState = type { ptr, ptr }
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declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #0
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declare void @runtime.trackPointer(ptr nocapture readonly, ptr, ptr) #0
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; Function Attrs: nounwind
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define hidden void @main.init(ptr %context) unnamed_addr #1 {
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entry:
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ret void
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}
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; Function Attrs: nounwind
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define hidden void @main.chanIntSend(ptr dereferenceable_or_null(32) %ch, ptr %context) unnamed_addr #1 {
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entry:
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%chan.blockedList = alloca %runtime.channelBlockedList, align 8
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%chan.value = alloca i32, align 4
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call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %chan.value)
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store i32 3, ptr %chan.value, align 4
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call void @llvm.lifetime.start.p0(i64 24, ptr nonnull %chan.blockedList)
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call void @runtime.chanSend(ptr %ch, ptr nonnull %chan.value, ptr nonnull %chan.blockedList, ptr undef) #3
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call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %chan.blockedList)
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call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %chan.value)
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ret void
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}
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; Function Attrs: argmemonly nocallback nofree nosync nounwind willreturn
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declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #2
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declare void @runtime.chanSend(ptr dereferenceable_or_null(32), ptr, ptr dereferenceable_or_null(24), ptr) #0
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; Function Attrs: argmemonly nocallback nofree nosync nounwind willreturn
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declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #2
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; Function Attrs: nounwind
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define hidden void @main.chanIntRecv(ptr dereferenceable_or_null(32) %ch, ptr %context) unnamed_addr #1 {
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entry:
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%chan.blockedList = alloca %runtime.channelBlockedList, align 8
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%chan.value = alloca i32, align 4
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call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %chan.value)
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call void @llvm.lifetime.start.p0(i64 24, ptr nonnull %chan.blockedList)
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%0 = call i1 @runtime.chanRecv(ptr %ch, ptr nonnull %chan.value, ptr nonnull %chan.blockedList, ptr undef) #3
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call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %chan.value)
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call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %chan.blockedList)
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ret void
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}
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declare i1 @runtime.chanRecv(ptr dereferenceable_or_null(32), ptr, ptr dereferenceable_or_null(24), ptr) #0
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; Function Attrs: nounwind
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define hidden void @main.chanZeroSend(ptr dereferenceable_or_null(32) %ch, ptr %context) unnamed_addr #1 {
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entry:
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%complit = alloca {}, align 8
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%chan.blockedList = alloca %runtime.channelBlockedList, align 8
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%stackalloc = alloca i8, align 1
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call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #3
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call void @llvm.lifetime.start.p0(i64 24, ptr nonnull %chan.blockedList)
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call void @runtime.chanSend(ptr %ch, ptr null, ptr nonnull %chan.blockedList, ptr undef) #3
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call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %chan.blockedList)
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ret void
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}
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; Function Attrs: nounwind
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define hidden void @main.chanZeroRecv(ptr dereferenceable_or_null(32) %ch, ptr %context) unnamed_addr #1 {
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entry:
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%chan.blockedList = alloca %runtime.channelBlockedList, align 8
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call void @llvm.lifetime.start.p0(i64 24, ptr nonnull %chan.blockedList)
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%0 = call i1 @runtime.chanRecv(ptr %ch, ptr null, ptr nonnull %chan.blockedList, ptr undef) #3
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call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %chan.blockedList)
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ret void
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}
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; Function Attrs: nounwind
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define hidden void @main.selectZeroRecv(ptr dereferenceable_or_null(32) %ch1, ptr dereferenceable_or_null(32) %ch2, ptr %context) unnamed_addr #1 {
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entry:
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%select.states.alloca = alloca [2 x %runtime.chanSelectState], align 8
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%select.send.value = alloca i32, align 4
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store i32 1, ptr %select.send.value, align 4
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call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %select.states.alloca)
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store ptr %ch1, ptr %select.states.alloca, align 8
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%select.states.alloca.repack1 = getelementptr inbounds %runtime.chanSelectState, ptr %select.states.alloca, i32 0, i32 1
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store ptr %select.send.value, ptr %select.states.alloca.repack1, align 4
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%0 = getelementptr inbounds [2 x %runtime.chanSelectState], ptr %select.states.alloca, i32 0, i32 1
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store ptr %ch2, ptr %0, align 8
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%.repack3 = getelementptr inbounds [2 x %runtime.chanSelectState], ptr %select.states.alloca, i32 0, i32 1, i32 1
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store ptr null, ptr %.repack3, align 4
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%select.result = call { i32, i1 } @runtime.tryChanSelect(ptr undef, ptr nonnull %select.states.alloca, i32 2, i32 2, ptr undef) #3
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call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %select.states.alloca)
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%1 = extractvalue { i32, i1 } %select.result, 0
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%2 = icmp eq i32 %1, 0
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br i1 %2, label %select.done, label %select.next
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select.done: ; preds = %select.body, %select.next, %entry
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ret void
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select.next: ; preds = %entry
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%3 = icmp eq i32 %1, 1
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br i1 %3, label %select.body, label %select.done
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select.body: ; preds = %select.next
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br label %select.done
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}
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declare { i32, i1 } @runtime.tryChanSelect(ptr, ptr, i32, i32, ptr) #0
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attributes #0 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
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attributes #1 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
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attributes #2 = { argmemonly nocallback nofree nosync nounwind willreturn }
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attributes #3 = { nounwind }
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