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Merged
titzer merged 15 commits into from
Apr 3, 2026
Merged

Add stack reconstruction methods for inlined contexts and wrap reconstruction points in SPC #595

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94855b1
Add SpcInlinedFrame
matthew-mojira Mar 20, 2026
9a38ea7
Add frame reconstructions methods and guard reconstruction points
matthew-mojira Mar 23, 2026
e5e4f05
Merge branch 'master' into pr/reconstruction
matthew-mojira Mar 23, 2026
731c9e7
Move function to a more sensible spot
matthew-mojira Mar 23, 2026
194f26d
Make the if statement one line
matthew-mojira Mar 25, 2026
f021600
Compute vfp for every inlined frame
matthew-mojira Mar 26, 2026
9bf2aeb
Uncomment stack reconstruction metrics
matthew-mojira Mar 26, 2026
e4b2d4a
Use optimized vfp calculation
matthew-mojira Mar 26, 2026
a7044bb
Use a single `rsp` adjustment in reconstructing stack frames
matthew-mojira Mar 31, 2026
7b8ae6d
Separate single-frame reconstruction into its own method
matthew-mojira Mar 31, 2026
036753d
Revert "Separate single-frame reconstruction into its own method"
matthew-mojira Mar 31, 2026
296ea0f
Fix wrong way indexing
matthew-mojira Mar 31, 2026
6b26972
Reapply "Separate single-frame reconstruction into its own method"
matthew-mojira Mar 31, 2026
a96f168
Restore vfp after out call
matthew-mojira Mar 31, 2026
f203d8e
Empty commit
matthew-mojira Apr 2, 2026
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177 changes: 150 additions & 27 deletions src/engine/compiler/SinglePassCompiler.v3
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Original file line number Diff line number Diff line change
Expand Up @@ -182,7 +182,8 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
// Emit function entry probe, if any.
if (!FeatureDisable.entryProbes && func.entry_probed) {
var probe = Instrumentation.getLocalProbe(module, func.func_index, 0);
emitProbe0(0, probe);
withReconstructedInlinedFrames(fun =>
emitProbe0(0, probe));
}

masm.current_fid = func.func_index;
Expand Down Expand Up @@ -214,8 +215,8 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
masm.bindLabel(label);

if (frames.length > 1) {
// no inlining yet: this should never happen
System.error("SpcError", "attempt to emit trap in inlined context");
unrefRegs();
emitReconstructStackFrames(frames);
} else {
masm.emit_mov_m_i(xenv.pc_slot, label.create_pos);
}
Expand Down Expand Up @@ -399,7 +400,8 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
if (last_probe == 0) return;
var probe = Instrumentation.getLocalProbe(module, func.func_index, last_probe);
last_probe = 0;
emitProbe0(it.pc, probe);
withReconstructedInlinedFrames(fun =>
emitProbe0(it.pc, probe));
if (Trace.compiler) traceOpcodeAndStack(true);
}
def emitProbe0(pc: int, probe: Probe) {
Expand Down Expand Up @@ -863,18 +865,21 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
masm.emit_inc_metric(Metrics.spc_dynamic_calls);
}
var func = module.functions[index];
var retpt = masm.newLabel(it.pc), wasmcall_label = masm.newLabel(it.pc);
// Load the instance (which must happen before frame is unwound).
var vsp_reg = allocTmpFixed(ValueKind.REF, regs.vsp);
var func_reg = allocTmpFixed(ValueKind.REF, regs.func_arg);
var tmp = allocTmp(ValueKind.REF);
emit_load_instance(tmp);

// Load the function, XXX: skip and compute function from instance + code on stack?
masm.emit_v3_Instance_functions_r_r(func_reg, tmp);
masm.emit_v3_Array_elem_r_ri(ValueKind.REF, func_reg, func_reg, func.func_index);
withReconstructedInlinedFrames(fun {
var retpt = masm.newLabel(it.pc), wasmcall_label = masm.newLabel(it.pc);
// Load the instance (which must happen before frame is unwound).
var vsp_reg = allocTmpFixed(ValueKind.REF, regs.vsp);
var func_reg = allocTmpFixed(ValueKind.REF, regs.func_arg);
var tmp = allocTmp(ValueKind.REF);
emit_load_instance(tmp);

// Load the function, XXX: skip and compute function from instance + code on stack?
masm.emit_v3_Instance_functions_r_r(func_reg, tmp);
masm.emit_v3_Array_elem_r_ri(ValueKind.REF, func_reg, func_reg, func.func_index);

emitCallToReg(func.sig, func_reg, vsp_reg, tmp, func.imp != null, tailCall);
emitCallToReg(func.sig, func_reg, vsp_reg, tmp, func.imp != null, tailCall);
});
}
def emitCallToReg(sig: SigDecl, func_reg: Reg, vsp_reg: Reg, tmp: Reg, checkHostCall: bool, tailCall: bool) {
var retpt = masm.newLabel(it.pc), wasmcall_label = masm.newLabel(it.pc);
Expand Down Expand Up @@ -1939,12 +1944,17 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
state.emitSaveAll(resolver, runtimeSpillMode);
emit_compute_vsp(regs.vsp, state.sp);
masm.emit_store_curstack_vsp(regs.vsp);
masm.emit_get_curstack(regs.runtime_arg0);
masm.emit_v3_set_X86_64Stack_rsp_r_r(regs.runtime_arg0, regs.sp);
masm.emit_push_X86_64Stack_rsp_r_r(regs.runtime_arg0);
emit_load_instance(regs.runtime_arg1);
masm.emit_mov_r_i(regs.runtime_arg2, arg1);
masm.emit_call_runtime_op(op);

def emit = fun {
masm.emit_get_curstack(regs.runtime_arg0);
masm.emit_v3_set_X86_64Stack_rsp_r_r(regs.runtime_arg0, regs.sp);
masm.emit_push_X86_64Stack_rsp_r_r(regs.runtime_arg0);
emit_load_instance(regs.runtime_arg1);
masm.emit_mov_r_i(regs.runtime_arg2, arg1);
masm.emit_call_runtime_op(op);
};
// Reconstruct stack frames across runtime calls that might (Wasm-level) trap.
if (canTrap) withReconstructedInlinedFrames(emit); else emit();
masm.emit_get_curstack(regs.scratch);
masm.emit_pop_X86_64Stack_rsp_r_r(regs.scratch);
dropN(args);
Expand All @@ -1956,13 +1966,18 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
state.emitSaveAll(resolver, runtimeSpillMode);
emit_compute_vsp(regs.vsp, state.sp);
masm.emit_store_curstack_vsp(regs.vsp);
masm.emit_get_curstack(regs.runtime_arg0);
masm.emit_v3_set_X86_64Stack_rsp_r_r(regs.runtime_arg0, regs.sp);
masm.emit_push_X86_64Stack_rsp_r_r(regs.runtime_arg0);
emit_load_instance(regs.runtime_arg1);
masm.emit_mov_r_i(regs.runtime_arg2, arg1);
masm.emit_mov_r_i(regs.runtime_arg3, arg2);
masm.emit_call_runtime_op(op);

def emit = fun {
masm.emit_get_curstack(regs.runtime_arg0);
masm.emit_v3_set_X86_64Stack_rsp_r_r(regs.runtime_arg0, regs.sp);
masm.emit_push_X86_64Stack_rsp_r_r(regs.runtime_arg0);
emit_load_instance(regs.runtime_arg1);
masm.emit_mov_r_i(regs.runtime_arg2, arg1);
masm.emit_mov_r_i(regs.runtime_arg3, arg2);
masm.emit_call_runtime_op(op);
};
// Reconstruct stack frames across runtime calls that might (Wasm-level) trap.
if (canTrap) withReconstructedInlinedFrames(emit); else emit();
masm.emit_get_curstack(regs.scratch);
masm.emit_pop_X86_64Stack_rsp_r_r(regs.scratch);
dropN(args);
Expand Down Expand Up @@ -2087,6 +2102,114 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
return label;
}
def getSpcInlinedFrameIp() -> long;
// Emit code to materialize stack frames for each inlined function.
def emitReconstructStackFrames(frames: Array<SpcFrame>) -> int {
Metrics.spc_static_reconst.val++;
masm.emit_inc_metric(Metrics.spc_dynamic_reconst);
def real_frame = frames[0];
masm.emit_mov_m_i(xenv.pc_slot, real_frame.pc);

// load instance
var inst_reg = allocTmp(ValueKind.REF);
masm.emit_mov_r_m(ValueKind.REF, inst_reg, frame.instance_slot);
var mem_reg = allocTmp(ValueKind.REF);
masm.emit_mov_r_m(ValueKind.REF, mem_reg, frame.mem0_base_slot);
// Load instance.functions
def func_reg = allocTmp(ValueKind.REF);
masm.emit_v3_Instance_functions_r_r(func_reg, inst_reg);
def vfp_reg = allocTmp(ValueKind.REF);
masm.emit_mov_r_m(ValueKind.REF, vfp_reg, frame.vfp_slot);
var prev_base_sp = int.view(frames[0].local_base_sp);
var wasm_func_reg = allocTmp(ValueKind.REF);

var inl_inst_reg: Reg, inl_mem0_reg: Reg;
if (is_inlined) {
inl_inst_reg = allocTmp(ValueKind.REF);
inl_mem0_reg = allocTmp(ValueKind.REF);
masm.emit_mov_r_m(ValueKind.REF, inl_inst_reg, frame.inlined_instance_slot);
masm.emit_mov_r_m(ValueKind.REF, inl_mem0_reg, frame.inlined_mem0_base_slot);
}

// Pre-allocate stack space for all reconstructed frames at once.
def total_space = (frames.length - 1) * (frame.frameSize + 8);
masm.emit_subw_r_i(regs.sp, total_space);

// Process the inlined frames (skip the outermost which already exists on native stack)
for (i = 1; i < frames.length; i++) {
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def frame_info = frames[i];
def cur_base_sp = int.view(frame_info.local_base_sp);
def delta = (cur_base_sp - prev_base_sp) * masm.valuerep.slot_size;
emitReconstructStackFrame(frame_info, frames.length - i - 1, delta,
wasm_func_reg, func_reg, inst_reg, mem_reg, vfp_reg, inl_inst_reg, inl_mem0_reg);
prev_base_sp = cur_base_sp;
}

return total_space;
}
def emitReconstructStackFrame(spcFrame: SpcFrame, offset: int, vfp_delta: int,
wasm_func_reg: Reg, func_reg: Reg, inst_reg: Reg, mem_reg: Reg, vfp_reg: Reg, inl_inst_reg: Reg, inl_mem0_reg: Reg) {
// Use inlined frame stub IP as return address for all reconstructed frames
def return_addr = getSpcInlinedFrameIp();

def frame_offset = offset * (frame.frameSize + 8);
// Write inlined frame stub IP as return address
def retaddr_slot = MasmAddr(regs.sp, frame_offset + frame.frameSize);
masm.emit_mov_m_l(retaddr_slot, return_addr);

// get functions[func_index] and save into frame
def wasm_func_slot = frame.wasm_func_slot.plus(frame_offset);
masm.emit_v3_Array_elem_r_ri(ValueKind.REF, wasm_func_reg, func_reg, spcFrame.func.func_index);
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@titzer titzer Mar 31, 2026

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I think this should be inst_reg instead of func_reg

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@matthew-mojira matthew-mojira Mar 31, 2026

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I don't think it should. This is indexing into the array instance.functions

masm.emit_mov_m_r(ValueKind.REF, wasm_func_slot, wasm_func_reg);

// Save instance
def instance_slot = frame.instance_slot.plus(frame_offset);
masm.emit_mov_m_r(ValueKind.REF, instance_slot, inst_reg);

// Save mem0 base
def mem0_base_slot = frame.mem0_base_slot.plus(frame_offset);
masm.emit_mov_m_r(ValueKind.REF, mem0_base_slot, mem_reg);

// Step vfp_reg by change in local_base_sp from previous frame and save
if (vfp_delta != 0) masm.emit_addw_r_i(vfp_reg, vfp_delta);
def vfp_slot = frame.vfp_slot.plus(frame_offset);
masm.emit_mov_m_r(ValueKind.REF, vfp_slot, vfp_reg);

// Save PC
def pc_slot = frame.pc_slot.plus(frame_offset);
masm.emit_mov_m_i(pc_slot, spcFrame.pc);

// Clear FrameAccessor
def accessor_slot = frame.accessor_slot.plus(frame_offset);
masm.emit_mov_m_l(accessor_slot, 0);

// if an inlined whamm probe, also grab inlined slots
if (is_inlined) {
def inl_instance_slot = frame.inlined_instance_slot.plus(frame_offset);
masm.emit_mov_m_r(ValueKind.REF, inl_instance_slot, inl_inst_reg);
def inl_mem0_base_slot = frame.inlined_mem0_base_slot.plus(frame_offset);
masm.emit_mov_m_r(ValueKind.REF, inl_mem0_base_slot, inl_mem0_reg);
} else {
def inl_instance_slot = frame.inlined_instance_slot.plus(frame_offset);
masm.emit_mov_m_l(inl_instance_slot, 0);
def inl_mem0_base_slot = frame.inlined_mem0_base_slot.plus(frame_offset);
masm.emit_mov_m_l(inl_mem0_base_slot, 0);
}
}
// Guards compiler code with frame reconstruction (if necessary).
def withReconstructedInlinedFrames(emit: void -> void) {
if (isInlined()) {
unrefRegs();
def space = emitReconstructStackFrames(snapshotFrames());
emit();
if (space > 0) {
masm.emit_addw_r_i(regs.sp, space);
masm.emit_mov_r_m(ValueKind.REF, regs.vfp, frame.vfp_slot);
}
} else {
emit();
}

}
def unsupported() {
success = false; // XXX: add opcode
}
Expand Down
30 changes: 29 additions & 1 deletion src/engine/x86-64/X86_64SinglePassCompiler.v3
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Original file line number Diff line number Diff line change
Expand Up @@ -1256,7 +1256,35 @@ class X86_64SpcModuleCode extends X86_64SpcCode {
}
// Reconstructs inlined interpreter frames for an inlined hardware trap context.
// Returns the new rsp to write into the ucontext (top of stack).
private def reconstructInlinedFramesForTrap(r_rsp: Pointer, inline_ctx: List<FuncLoc>) -> Pointer;
private def reconstructInlinedFramesForTrap(r_rsp: Pointer, inline_ctx: List<FuncLoc>) -> Pointer {
def frames: Array<FuncLoc> = Lists.toArray(inline_ctx);
def outer = frames[frames.length - 1];
def inlined = frames[0 ... (frames.length - 1)];
def count = inlined.length;

// set outermost pc in the real frame
(r_rsp + X86_64InterpreterFrame.curpc.offset).store<int>(outer.pc);

// Read instance from the real outer frame (shared across all inlined frames)
var instance = (r_rsp + X86_64InterpreterFrame.instance.offset).load<Instance>();

// Push inlined frames
for (i = count - 1; i >= 0; i--) {
var fid = inlined[i].func_index;
var pc = inlined[i].pc;

r_rsp += -8;
r_rsp.store<Pointer>(INLINED_FRAME_STUB.start);

r_rsp += -X86_64InterpreterFrame.size; // move rsp?
// write func, pc, frame accessor
var wasm_func = WasmFunction.!(instance.functions[fid]);
(r_rsp + X86_64InterpreterFrame.wasm_func.offset).store<WasmFunction>(wasm_func);
(r_rsp + X86_64InterpreterFrame.curpc.offset).store<int>(pc);
(r_rsp + X86_64InterpreterFrame.accessor.offset).store<X86_64FrameAccessor>(null);
}
return r_rsp;
}
// Look up the source {pc} of a location {i} in this code. Returns {-1} if no exact entry is found.
// Return addresses are treated differently than other addresses in the code.
def lookupPc(ip: Pointer, isRetAddr: bool) -> List<FuncLoc> {
Expand Down
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