Stream: git-wasmtime

Topic: wasmtime / issue #10564 [DI] Wrong live range for a varia...

view this post on Zulip Wasmtime GitHub notifications bot (Apr 10 2025 at 21:08):

SingleAccretion opened issue #10564:

Reproduction:

__attribute__((noinline)) int InvalidateRegisters() {
    volatile int x = 0;
    int r1 = -1;
    int r2 = -2;
    int r3 = -3;
    int r4 = -4;
    int r5 = -5;
    int r6 = -6;
    int r7 = -7;
    int r8 = -8;
    return r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8;
}

__attribute__((noinline)) int NoInlineSideEffect_1(int b, int c) {
    InvalidateRegisters();
    volatile int x[3] = {1, 2, 3};
    return x[(b + c) >> 16];
}

__attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
{
    int t = b & 431;
    NoInlineSideEffect_1(t, b);
    return 0;
}

int main() {
    volatile int x = 1;
    VariableLiveRangeStartIsCorrect(42);
}

> clang -O2 -g -o main.wasm main.cpp
> lldb -o "b VariableLiveRangeStartIsCorrect" -o "r" -- wasmtime -Ddebug-info -Oopt-level=2 -Ccache=n main.wasm
> (lldb) s
> (lldb) v

Expected result: b = 42.
Actual result:

Process 65804 stopped
* thread #1, name = 'main', stop reason = step in
    frame #0: 0x000001b883d31113 JIT(0x1b883f01010)`VariableLiveRangeStartIsCorrect(b=-2082057552) at main.cpp:20:5
   17   __attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
   18   {
   19       int t = b & 431;
-> 20       NoInlineSideEffect_1(t, b);
   21       return 0;
   22   }
   23
(lldb) v
(WasmtimeVMContext *) __vmctx = 0x000001b883e652b0
(int) b = -2082057552
(int) t = <no location, value may have been optimized out>

Cause: confusion over what the live range endpoints represent. See more notes https://github.com/bytecodealliance/wasmtime/issues/9716.

view this post on Zulip Wasmtime GitHub notifications bot (Apr 10 2025 at 21:10):

SingleAccretion edited issue #10564:

Reproduction:

__attribute__((noinline)) int InvalidateRegisters() {
    volatile int x = 0;
    int r1 = -1;
    int r2 = -2;
    int r3 = -3;
    int r4 = -4;
    int r5 = -5;
    int r6 = -6;
    int r7 = -7;
    int r8 = -8;
    return r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8;
}

__attribute__((noinline)) int NoInlineSideEffect_1(int b, int c) {
    InvalidateRegisters();
    volatile int x[3] = {1, 2, 3};
    return x[(b + c) >> 16];
}

__attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
{
    int t = b & 431;
    NoInlineSideEffect_1(t, b);
    return 0;
}

int main() {
    volatile int x = 1;
    VariableLiveRangeStartIsCorrect(42);
}

> clang -O2 -g -o main.wasm main.cpp
> lldb -o "b VariableLiveRangeStartIsCorrect" -o "r" -- wasmtime -Ddebug-info -Oopt-level=2 -Ccache=n main.wasm
> (lldb) s
> (lldb) v

Expected result: b = 42.
Actual result:

Process 65804 stopped
* thread #1, name = 'main', stop reason = step in
    frame #0: 0x000001b883d31113 JIT(0x1b883f01010)`VariableLiveRangeStartIsCorrect(b=-2082057552) at main.cpp:20:5
   17   __attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
   18   {
   19       int t = b & 431;
-> 20       NoInlineSideEffect_1(t, b);
   21       return 0;
   22   }
   23
(lldb) v
(WasmtimeVMContext *) __vmctx = 0x000001b883e652b0
(int) b = -2082057552
(int) t = <no location, value may have been optimized out>

Cause: confusion over what the live range endpoints represent. See more notes https://github.com/bytecodealliance/wasmtime/issues/9716.

Excerpt from the trace log:

|BB|Inst   |IP |VL0     |VL4294967294|
|--|-------|---|--------|------------|
|B0|Inst 0 |33 |    |   |    |       |
|  |Inst 1 |36 |    |   |    |       |
|  |Inst 2 |51 |v194|p6i|v192|p7i    | ; NoInlineSideEffect_1(t, b)
|  |Inst 3 |56 |*   |   |*   |p13i   |
|B1|Inst 4 |56 |*   |   |*   |p13i   |
|  |Inst 5 |58 |*   |   |*   |p13i   |
|  |Inst 6 |58 |*   |   |*   |       |

block0:
  movq    %rdx, %rsi
  andl $0x1af, %edx
  movq    %rsi, %rcx
  movq    %rdi, %r13
  movq    %r13, %rsi
  call    User(userextname0) ; NoInlineSideEffect_1(t, b)
  jmp     label1

view this post on Zulip Wasmtime GitHub notifications bot (Apr 10 2025 at 21:11):

SingleAccretion edited issue #10564:

Reproduction:

__attribute__((noinline)) int InvalidateRegisters() {
    volatile int x = 0;
    int r1 = -1;
    int r2 = -2;
    int r3 = -3;
    int r4 = -4;
    int r5 = -5;
    int r6 = -6;
    int r7 = -7;
    int r8 = -8;
    return r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8;
}

__attribute__((noinline)) int NoInlineSideEffect_1(int b, int c) {
    InvalidateRegisters();
    volatile int x[3] = {1, 2, 3};
    return x[(b + c) >> 16];
}

__attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
{
    int t = b & 431;
    NoInlineSideEffect_1(t, b);
    return 0;
}

int main() {
    volatile int x = 1;
    VariableLiveRangeStartIsCorrect(42);
}

> clang -O2 -g -o main.wasm main.cpp
> lldb -o "b VariableLiveRangeStartIsCorrect" -o "r" -- wasmtime -Ddebug-info -Oopt-level=2 -Ccache=n main.wasm
> (lldb) s
> (lldb) v

Expected result: b = 42.
Actual result:

Process 65804 stopped
* thread #1, name = 'main', stop reason = step in
    frame #0: 0x000001b883d31113 JIT(0x1b883f01010)`VariableLiveRangeStartIsCorrect(b=-2082057552) at main.cpp:20:5
   17   __attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
   18   {
   19       int t = b & 431;
-> 20       NoInlineSideEffect_1(t, b);
   21       return 0;
   22   }
   23
(lldb) v
(WasmtimeVMContext *) __vmctx = 0x000001b883e652b0
(int) b = -2082057552
(int) t = <no location, value may have been optimized out>

Cause: confusion over what the live range endpoints represent. See more notes https://github.com/bytecodealliance/wasmtime/issues/9716.

Excerpt from the trace log:

|BB|Inst   |IP |VL0     |VL4294967294|
|--|-------|---|--------|------------|
|B0|Inst 0 |33 |    |   |    |       |
|  |Inst 1 |36 |    |   |    |       |
|  |Inst 2 |51 |v194|p6i|v192|p7i    | ; NoInlineSideEffect_1(t, b)
|  |Inst 3 |56 |*   |   |*   |p13i   |
|B1|Inst 4 |56 |*   |   |*   |p13i   |
|  |Inst 5 |58 |*   |   |*   |p13i   |
|  |Inst 6 |58 |*   |   |*   |       |

block0:
  movq    %rdx, %rsi
  andl $0x1af, %edx ; Invalidates the value of p6i
  movq    %rsi, %rcx
  movq    %rdi, %r13
  movq    %r13, %rsi
  call    User(userextname0) ; NoInlineSideEffect_1(t, b)
  jmp     label1

view this post on Zulip Wasmtime GitHub notifications bot (Apr 15 2025 at 21:16):

SingleAccretion closed issue #10564:

Reproduction:

__attribute__((noinline)) int InvalidateRegisters() {
    volatile int x = 0;
    int r1 = -1;
    int r2 = -2;
    int r3 = -3;
    int r4 = -4;
    int r5 = -5;
    int r6 = -6;
    int r7 = -7;
    int r8 = -8;
    return r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8;
}

__attribute__((noinline)) int NoInlineSideEffect_1(int b, int c) {
    InvalidateRegisters();
    volatile int x[3] = {1, 2, 3};
    return x[(b + c) >> 16];
}

__attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
{
    int t = b & 431;
    NoInlineSideEffect_1(t, b);
    return 0;
}

int main() {
    volatile int x = 1;
    VariableLiveRangeStartIsCorrect(42);
}

> clang -O2 -g -o main.wasm main.cpp
> lldb -o "b VariableLiveRangeStartIsCorrect" -o "r" -- wasmtime -Ddebug-info -Oopt-level=2 -Ccache=n main.wasm
> (lldb) s
> (lldb) v

Expected result: b = 42.
Actual result:

Process 65804 stopped
* thread #1, name = 'main', stop reason = step in
    frame #0: 0x000001b883d31113 JIT(0x1b883f01010)`VariableLiveRangeStartIsCorrect(b=-2082057552) at main.cpp:20:5
   17   __attribute__((noinline)) int VariableLiveRangeStartIsCorrect(int b)
   18   {
   19       int t = b & 431;
-> 20       NoInlineSideEffect_1(t, b);
   21       return 0;
   22   }
   23
(lldb) v
(WasmtimeVMContext *) __vmctx = 0x000001b883e652b0
(int) b = -2082057552
(int) t = <no location, value may have been optimized out>

Cause: confusion over what the live range endpoints represent. See more notes https://github.com/bytecodealliance/wasmtime/issues/9716.

Excerpt from the trace log:

|BB|Inst   |IP |VL0     |VL4294967294|
|--|-------|---|--------|------------|
|B0|Inst 0 |33 |    |   |    |       |
|  |Inst 1 |36 |    |   |    |       |
|  |Inst 2 |51 |v194|p6i|v192|p7i    | ; NoInlineSideEffect_1(t, b)
|  |Inst 3 |56 |*   |   |*   |p13i   |
|B1|Inst 4 |56 |*   |   |*   |p13i   |
|  |Inst 5 |58 |*   |   |*   |p13i   |
|  |Inst 6 |58 |*   |   |*   |       |

block0:
  movq    %rdx, %rsi
  andl $0x1af, %edx ; Invalidates the value of p6i
  movq    %rsi, %rcx
  movq    %rdi, %r13
  movq    %r13, %rsi
  call    User(userextname0) ; NoInlineSideEffect_1(t, b)
  jmp     label1

Last updated: Dec 06 2025 at 06:05 UTC