ab47cea055
Bug 1790 ("musttail call must precede a ret with an optional bitcast")
is caused by the GC stack slot pass inserting a store instruction
between a musttail call and a return instruction. This is not allowed in
LLVM IR.
One solution would be to remove the musttail. That would probably work,
but 1) the go-llvm API doesn't support this and 2) this might have
unforeseen consequences. What I've done in this commit is to move the
store instruction to a position earlier in the basic block, just after
the last access to the GC stack slot alloca.
Thanks to @fgsch for a very small repro, which I've used as a regression
test.
105 строки
3,2 КиБ
LLVM
105 строки
3,2 КиБ
LLVM
target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
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target triple = "wasm32-unknown-unknown-wasm"
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%runtime.stackChainObject = type { %runtime.stackChainObject*, i32 }
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@runtime.stackChainStart = external global %runtime.stackChainObject*
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@someGlobal = global i8 3
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declare void @runtime.trackPointer(i8* nocapture readonly)
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declare noalias nonnull i8* @runtime.alloc(i32)
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; Generic function that returns a pointer (that must be tracked).
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define i8* @getPointer() {
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ret i8* @someGlobal
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}
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define i8* @needsStackSlots() {
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; Tracked pointer. Although, in this case the value is immediately returned
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; so tracking it is not really necessary.
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%ptr = call i8* @runtime.alloc(i32 4)
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call void @runtime.trackPointer(i8* %ptr)
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; Restoring the stack pointer can happen at this position, before the return.
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; This avoids issues with tail calls.
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call void @someArbitraryFunction()
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%val = load i8, i8* @someGlobal
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ret i8* %ptr
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}
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; Check some edge cases of pointer tracking.
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define i8* @needsStackSlots2() {
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; Only one stack slot should be created for this (but at the moment, one is
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; created for each call to runtime.trackPointer).
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%ptr1 = call i8* @getPointer()
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call void @runtime.trackPointer(i8* %ptr1)
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call void @runtime.trackPointer(i8* %ptr1)
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call void @runtime.trackPointer(i8* %ptr1)
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; Create a pointer that does not need to be tracked (but is tracked).
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%ptr2 = getelementptr i8, i8* @someGlobal, i32 0
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call void @runtime.trackPointer(i8* %ptr2)
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; Here is finally the point where an allocation happens.
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%unused = call i8* @runtime.alloc(i32 4)
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call void @runtime.trackPointer(i8* %unused)
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ret i8* %ptr1
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}
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; Return a pointer from a caller. Because it doesn't allocate, no stack objects
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; need to be created.
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define i8* @noAllocatingFunction() {
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%ptr = call i8* @getPointer()
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call void @runtime.trackPointer(i8* %ptr)
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ret i8* %ptr
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}
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define i8* @fibNext(i8* %x, i8* %y) {
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%x.val = load i8, i8* %x
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%y.val = load i8, i8* %y
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%out.val = add i8 %x.val, %y.val
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%out.alloc = call i8* @runtime.alloc(i32 1)
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call void @runtime.trackPointer(i8* %out.alloc)
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store i8 %out.val, i8* %out.alloc
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ret i8* %out.alloc
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}
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define i8* @allocLoop() {
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entry:
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%entry.x = call i8* @runtime.alloc(i32 1)
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call void @runtime.trackPointer(i8* %entry.x)
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%entry.y = call i8* @runtime.alloc(i32 1)
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call void @runtime.trackPointer(i8* %entry.y)
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store i8 1, i8* %entry.y
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br label %loop
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loop:
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%prev.y = phi i8* [ %entry.y, %entry ], [ %prev.x, %loop ]
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%prev.x = phi i8* [ %entry.x, %entry ], [ %next.x, %loop ]
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call void @runtime.trackPointer(i8* %prev.x)
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call void @runtime.trackPointer(i8* %prev.y)
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%next.x = call i8* @fibNext(i8* %prev.x, i8* %prev.y)
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call void @runtime.trackPointer(i8* %next.x)
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%next.x.val = load i8, i8* %next.x
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%loop.done = icmp ult i8 40, %next.x.val
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br i1 %loop.done, label %end, label %loop
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end:
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ret i8* %next.x
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}
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declare [32 x i8]* @arrayAlloc()
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define void @testGEPBitcast() {
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%arr = call [32 x i8]* @arrayAlloc()
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%arr.bitcast = getelementptr [32 x i8], [32 x i8]* %arr, i32 0, i32 0
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call void @runtime.trackPointer(i8* %arr.bitcast)
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%other = call i8* @runtime.alloc(i32 1)
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call void @runtime.trackPointer(i8* %other)
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ret void
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}
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define void @someArbitraryFunction() {
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ret void
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}
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