diff options
| -rw-r--r-- | src/ir/effects.h | 16 | ||||
| -rw-r--r-- | test/lit/passes/vacuum-tnh.wast | 13 | ||||
| -rw-r--r-- | test/wasm2js/br_table_to_loop.2asm.js.opt | 4 |
3 files changed, 16 insertions, 17 deletions
diff --git a/src/ir/effects.h b/src/ir/effects.h index fe2520299..893ff2cae 100644 --- a/src/ir/effects.h +++ b/src/ir/effects.h @@ -122,10 +122,6 @@ public: // *do* mark a potentially infinite number of allocations as trapping, as all // VMs would trap eventually, and the same for potentially infinite recursion, // etc. - // * We assume that VMs will timeout eventually, so any loop that we cannot - // prove terminates is considered to trap. (Some VMs might not have - // such timeouts, but even they will error before the heat death of the - // universe, which is a kind of trap.) bool trap = false; // A trap from an instruction like a load or div/rem, which may trap on corner // cases. If we do not ignore implicit traps then these are counted as a trap. @@ -145,6 +141,9 @@ public: // If this expression contains 'pop's that are not enclosed in 'catch' body. // For example, (drop (pop i32)) should set this to true. bool danglingPop = false; + // Whether this code may "hang" and not eventually complete. An infinite loop, + // or a continuation that is never continued, are examples of that. + bool mayNotReturn = false; // Helper functions to check for various effect types @@ -184,7 +183,7 @@ public: bool hasNonTrapSideEffects() const { return localsWritten.size() > 0 || danglingPop || writesGlobalState() || - throws() || transfersControlFlow(); + throws() || transfersControlFlow() || mayNotReturn; } bool hasSideEffects() const { return trap || hasNonTrapSideEffects(); } @@ -419,12 +418,7 @@ private: void visitIf(If* curr) {} void visitLoop(Loop* curr) { if (curr->name.is() && parent.breakTargets.erase(curr->name) > 0) { - // Breaks to this loop exist, which we just removed as they do not have - // further effect outside of this loop. One additional thing we need to - // take into account is infinite looping, which is a noticeable side - // effect we can't normally remove - eventually the VM will time out and - // error (see more details in the comment on trapping above). - parent.implicitTrap = true; + parent.mayNotReturn = true; } } void visitBreak(Break* curr) { parent.breakTargets.insert(curr->name); } diff --git a/test/lit/passes/vacuum-tnh.wast b/test/lit/passes/vacuum-tnh.wast index 6b0907989..e4ce9765d 100644 --- a/test/lit/passes/vacuum-tnh.wast +++ b/test/lit/passes/vacuum-tnh.wast @@ -186,7 +186,14 @@ ) ;; YESTNH: (func $drop-loop (type $none_=>_none) - ;; YESTNH-NEXT: (nop) + ;; YESTNH-NEXT: (drop + ;; YESTNH-NEXT: (loop $loop (result i32) + ;; YESTNH-NEXT: (br_if $loop + ;; YESTNH-NEXT: (i32.const 1) + ;; YESTNH-NEXT: ) + ;; YESTNH-NEXT: (i32.const 10) + ;; YESTNH-NEXT: ) + ;; YESTNH-NEXT: ) ;; YESTNH-NEXT: ) ;; NO_TNH: (func $drop-loop (type $none_=>_none) ;; NO_TNH-NEXT: (drop @@ -199,8 +206,8 @@ ;; NO_TNH-NEXT: ) ;; NO_TNH-NEXT: ) (func $drop-loop - ;; A loop has effects, since it might infinite loop (and hit a timeout trap - ;; eventually), so we do not vacuum it out unless we are ignoring traps. + ;; A loop has the effect of potentially being infinite. Even in TNH mode we + ;; do not optimize out such loops. (drop (loop $loop (result i32) (br_if $loop diff --git a/test/wasm2js/br_table_to_loop.2asm.js.opt b/test/wasm2js/br_table_to_loop.2asm.js.opt index 5c6fa5e7f..4c9f97311 100644 --- a/test/wasm2js/br_table_to_loop.2asm.js.opt +++ b/test/wasm2js/br_table_to_loop.2asm.js.opt @@ -1,6 +1,4 @@ -function wasm2js_trap() { throw new Error('abort'); } - function asmFunc(imports) { var Math_imul = Math.imul; var Math_fround = Math.fround; @@ -13,7 +11,7 @@ function asmFunc(imports) { var Math_trunc = Math.trunc; var Math_sqrt = Math.sqrt; function $0() { - wasm2js_trap(); + while (1) continue; } function $1() { |