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fix: handle nest tostack in shadowstack pass #2792

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merged 1 commit into from
Nov 17, 2023
Merged

fix: handle nest tostack in shadowstack pass #2792

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15 changes: 9 additions & 6 deletions src/passes/shadowstack.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -159,18 +159,21 @@ type TempMap = Map<TypeRef,LocalIndex>;

/** Attempts to match the `__tostack(value)` pattern. Returns `value` if a match, otherwise `0`. */
function matchPattern(module: Module, expr: ExpressionRef): ExpressionRef {
if (
let isFound = false;
while (
_BinaryenExpressionGetId(expr) == ExpressionId.Call &&
module.readStringCached(_BinaryenCallGetTarget(expr)) == BuiltinNames.tostack
) {
assert(_BinaryenCallGetNumOperands(expr) == 1);
return _BinaryenCallGetOperandAt(expr, 0);
expr = _BinaryenCallGetOperandAt(expr, 0);
isFound = true;
}
return 0;
if (!isFound) return 0;
return expr;
}

/** Tests whether a `value` matched by `matchTostack` needs a slot. */
function needsSlot(module: Module, value: ExpressionRef): bool {
function needsSlot(value: ExpressionRef): bool {
switch (_BinaryenExpressionGetId(value)) {
// no need to stack null pointers
case ExpressionId.Const: return !isConstZero(value);
Expand Down Expand Up @@ -344,7 +347,7 @@ export class ShadowStackPass extends Pass {
let operand = operands[i];
let match = matchPattern(module, operand);
if (!match) continue;
if (!needsSlot(module, match)) {
if (!needsSlot(match)) {
operands[i] = match;
continue;
}
Expand Down Expand Up @@ -434,7 +437,7 @@ export class ShadowStackPass extends Pass {
let value = _BinaryenLocalSetGetValue(localSet);
let match = matchPattern(module, value);
if (!match) return;
if (!needsSlot(module, match)) {
if (!needsSlot(match)) {
_BinaryenLocalSetSetValue(localSet, match);
return;
}
Expand Down
8 changes: 2 additions & 6 deletions tests/compiler/resolve-unary.debug.wat
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Original file line number Diff line number Diff line change
Expand Up @@ -3753,10 +3753,8 @@
call $~lib/builtins/abort
unreachable
end
global.get $~lib/memory/__stack_pointer
global.get $resolve-unary/bar
local.tee $6
i32.store
local.set $6
global.get $~lib/memory/__stack_pointer
local.get $6
i32.store offset=12
Expand Down Expand Up @@ -3789,10 +3787,8 @@
call $~lib/builtins/abort
unreachable
end
global.get $~lib/memory/__stack_pointer
global.get $resolve-unary/bar
local.tee $6
i32.store
local.set $6
global.get $~lib/memory/__stack_pointer
local.get $6
i32.store offset=12
Expand Down
8 changes: 0 additions & 8 deletions tests/compiler/resolve-unary.release.wat
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Original file line number Diff line number Diff line change
Expand Up @@ -2626,10 +2626,6 @@
global.get $~lib/memory/__stack_pointer
local.tee $0
global.get $resolve-unary/bar
local.tee $1
i32.store
local.get $0
local.get $1
i32.store offset=12
local.get $0
i32.const 3680
Expand All @@ -2655,10 +2651,6 @@
global.get $~lib/memory/__stack_pointer
local.tee $0
global.get $resolve-unary/bar
local.tee $1
i32.store
local.get $0
local.get $1
i32.store offset=12
local.get $0
i32.const 3712
Expand Down