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wasm: avoid miscompile with ThinLTO

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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).
This commit is contained in:
Ayke van Laethem
2023-01-17 22:53:38 +01:00
committed by Ron Evans
parent 27824e3c80
commit c41a212712
16 changed files with 122 additions and 79 deletions
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compiler/testdata/slice.ll
Vendored
+28 -15
View File
@@ -5,7 +5,7 @@ target triple = "wasm32-unknown-wasi"
declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #0
declare void @runtime.trackPointer(ptr nocapture readonly, ptr) #0
declare void @runtime.trackPointer(ptr nocapture readonly, ptr, ptr) #0
; Function Attrs: nounwind
define hidden void @main.init(ptr %context) unnamed_addr #1 {
@@ -46,8 +46,9 @@ declare void @runtime.lookupPanic(ptr) #0
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.sliceAppendValues(ptr %ints.data, i32 %ints.len, i32 %ints.cap, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%varargs = call ptr @runtime.alloc(i32 12, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %varargs, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %varargs, ptr nonnull %stackalloc, ptr undef) #2
store i32 1, ptr %varargs, align 4
%0 = getelementptr inbounds [3 x i32], ptr %varargs, i32 0, i32 1
store i32 2, ptr %0, align 4
@@ -60,7 +61,7 @@ entry:
%2 = insertvalue { ptr, i32, i32 } undef, ptr %append.newPtr, 0
%3 = insertvalue { ptr, i32, i32 } %2, i32 %append.newLen, 1
%4 = insertvalue { ptr, i32, i32 } %3, i32 %append.newCap, 2
call void @runtime.trackPointer(ptr %append.newPtr, ptr undef) #2
call void @runtime.trackPointer(ptr %append.newPtr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %4
}
@@ -69,6 +70,7 @@ declare { ptr, i32, i32 } @runtime.sliceAppend(ptr, ptr nocapture readonly, i32,
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.sliceAppendSlice(ptr %ints.data, i32 %ints.len, i32 %ints.cap, ptr %added.data, i32 %added.len, i32 %added.cap, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%append.new = call { ptr, i32, i32 } @runtime.sliceAppend(ptr %ints.data, ptr %added.data, i32 %ints.len, i32 %ints.cap, i32 %added.len, i32 4, ptr undef) #2
%append.newPtr = extractvalue { ptr, i32, i32 } %append.new, 0
%append.newLen = extractvalue { ptr, i32, i32 } %append.new, 1
@@ -76,7 +78,7 @@ entry:
%0 = insertvalue { ptr, i32, i32 } undef, ptr %append.newPtr, 0
%1 = insertvalue { ptr, i32, i32 } %0, i32 %append.newLen, 1
%2 = insertvalue { ptr, i32, i32 } %1, i32 %append.newCap, 2
call void @runtime.trackPointer(ptr %append.newPtr, ptr undef) #2
call void @runtime.trackPointer(ptr %append.newPtr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %2
}
@@ -92,6 +94,7 @@ declare i32 @runtime.sliceCopy(ptr nocapture writeonly, ptr nocapture readonly,
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.makeByteSlice(i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%slice.maxcap = icmp slt i32 %len, 0
br i1 %slice.maxcap, label %slice.throw, label %slice.next
@@ -100,7 +103,7 @@ slice.next: ; preds = %entry
%0 = insertvalue { ptr, i32, i32 } undef, ptr %makeslice.buf, 0
%1 = insertvalue { ptr, i32, i32 } %0, i32 %len, 1
%2 = insertvalue { ptr, i32, i32 } %1, i32 %len, 2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %2
slice.throw: ; preds = %entry
@@ -113,6 +116,7 @@ declare void @runtime.slicePanic(ptr) #0
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.makeInt16Slice(i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%slice.maxcap = icmp slt i32 %len, 0
br i1 %slice.maxcap, label %slice.throw, label %slice.next
@@ -122,7 +126,7 @@ slice.next: ; preds = %entry
%0 = insertvalue { ptr, i32, i32 } undef, ptr %makeslice.buf, 0
%1 = insertvalue { ptr, i32, i32 } %0, i32 %len, 1
%2 = insertvalue { ptr, i32, i32 } %1, i32 %len, 2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %2
slice.throw: ; preds = %entry
@@ -133,6 +137,7 @@ slice.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.makeArraySlice(i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%slice.maxcap = icmp ugt i32 %len, 1431655765
br i1 %slice.maxcap, label %slice.throw, label %slice.next
@@ -142,7 +147,7 @@ slice.next: ; preds = %entry
%0 = insertvalue { ptr, i32, i32 } undef, ptr %makeslice.buf, 0
%1 = insertvalue { ptr, i32, i32 } %0, i32 %len, 1
%2 = insertvalue { ptr, i32, i32 } %1, i32 %len, 2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %2
slice.throw: ; preds = %entry
@@ -153,6 +158,7 @@ slice.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.makeInt32Slice(i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%slice.maxcap = icmp ugt i32 %len, 1073741823
br i1 %slice.maxcap, label %slice.throw, label %slice.next
@@ -162,7 +168,7 @@ slice.next: ; preds = %entry
%0 = insertvalue { ptr, i32, i32 } undef, ptr %makeslice.buf, 0
%1 = insertvalue { ptr, i32, i32 } %0, i32 %len, 1
%2 = insertvalue { ptr, i32, i32 } %1, i32 %len, 2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice.buf, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %2
slice.throw: ; preds = %entry
@@ -173,17 +179,19 @@ slice.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden ptr @main.Add32(ptr %p, i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = getelementptr i8, ptr %p, i32 %len
call void @runtime.trackPointer(ptr %0, ptr undef) #2
call void @runtime.trackPointer(ptr %0, ptr nonnull %stackalloc, ptr undef) #2
ret ptr %0
}
; Function Attrs: nounwind
define hidden ptr @main.Add64(ptr %p, i64 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = trunc i64 %len to i32
%1 = getelementptr i8, ptr %p, i32 %0
call void @runtime.trackPointer(ptr %1, ptr undef) #2
call void @runtime.trackPointer(ptr %1, ptr nonnull %stackalloc, ptr undef) #2
ret ptr %1
}
@@ -206,8 +214,9 @@ declare void @runtime.sliceToArrayPointerPanic(ptr) #0
; Function Attrs: nounwind
define hidden ptr @main.SliceToArrayConst(ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%makeslice = call ptr @runtime.alloc(i32 24, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice, ptr undef) #2
call void @runtime.trackPointer(ptr nonnull %makeslice, ptr nonnull %stackalloc, ptr undef) #2
br i1 false, label %slicetoarray.throw, label %slicetoarray.next
slicetoarray.next: ; preds = %entry
@@ -220,6 +229,7 @@ slicetoarray.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.SliceInt(ptr dereferenceable_or_null(4) %ptr, i32 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = icmp ugt i32 %len, 1073741823
%1 = icmp eq ptr %ptr, null
%2 = icmp ne i32 %len, 0
@@ -231,7 +241,7 @@ unsafe.Slice.next: ; preds = %entry
%5 = insertvalue { ptr, i32, i32 } undef, ptr %ptr, 0
%6 = insertvalue { ptr, i32, i32 } %5, i32 %len, 1
%7 = insertvalue { ptr, i32, i32 } %6, i32 %len, 2
call void @runtime.trackPointer(ptr %ptr, ptr undef) #2
call void @runtime.trackPointer(ptr %ptr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %7
unsafe.Slice.throw: ; preds = %entry
@@ -244,6 +254,7 @@ declare void @runtime.unsafeSlicePanic(ptr) #0
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.SliceUint16(ptr dereferenceable_or_null(1) %ptr, i16 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = icmp eq ptr %ptr, null
%1 = icmp ne i16 %len, 0
%2 = and i1 %0, %1
@@ -254,7 +265,7 @@ unsafe.Slice.next: ; preds = %entry
%4 = insertvalue { ptr, i32, i32 } undef, ptr %ptr, 0
%5 = insertvalue { ptr, i32, i32 } %4, i32 %3, 1
%6 = insertvalue { ptr, i32, i32 } %5, i32 %3, 2
call void @runtime.trackPointer(ptr %ptr, ptr undef) #2
call void @runtime.trackPointer(ptr %ptr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %6
unsafe.Slice.throw: ; preds = %entry
@@ -265,6 +276,7 @@ unsafe.Slice.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.SliceUint64(ptr dereferenceable_or_null(4) %ptr, i64 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = icmp ugt i64 %len, 1073741823
%1 = icmp eq ptr %ptr, null
%2 = icmp ne i64 %len, 0
@@ -277,7 +289,7 @@ unsafe.Slice.next: ; preds = %entry
%6 = insertvalue { ptr, i32, i32 } undef, ptr %ptr, 0
%7 = insertvalue { ptr, i32, i32 } %6, i32 %5, 1
%8 = insertvalue { ptr, i32, i32 } %7, i32 %5, 2
call void @runtime.trackPointer(ptr %ptr, ptr undef) #2
call void @runtime.trackPointer(ptr %ptr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %8
unsafe.Slice.throw: ; preds = %entry
@@ -288,6 +300,7 @@ unsafe.Slice.throw: ; preds = %entry
; Function Attrs: nounwind
define hidden { ptr, i32, i32 } @main.SliceInt64(ptr dereferenceable_or_null(4) %ptr, i64 %len, ptr %context) unnamed_addr #1 {
entry:
%stackalloc = alloca i8, align 1
%0 = icmp ugt i64 %len, 1073741823
%1 = icmp eq ptr %ptr, null
%2 = icmp ne i64 %len, 0
@@ -300,7 +313,7 @@ unsafe.Slice.next: ; preds = %entry
%6 = insertvalue { ptr, i32, i32 } undef, ptr %ptr, 0
%7 = insertvalue { ptr, i32, i32 } %6, i32 %5, 1
%8 = insertvalue { ptr, i32, i32 } %7, i32 %5, 2
call void @runtime.trackPointer(ptr %ptr, ptr undef) #2
call void @runtime.trackPointer(ptr %ptr, ptr nonnull %stackalloc, ptr undef) #2
ret { ptr, i32, i32 } %8
unsafe.Slice.throw: ; preds = %entry