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Backport #187484 #194

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17 changes: 14 additions & 3 deletions llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1836,6 +1836,8 @@ bool WebAssemblyCFGStackify::fixCallUnwindMismatches(MachineFunction &MF) {
for (auto &MI : reverse(MBB)) {
if (WebAssembly::isTry(MI.getOpcode()))
EHPadStack.pop_back();
else if (MI.getOpcode() == WebAssembly::DELEGATE)
EHPadStack.push_back(MI.getOperand(0).getMBB());
else if (WebAssembly::isCatch(MI.getOpcode()))
EHPadStack.push_back(MI.getParent());

Expand All @@ -1847,6 +1849,8 @@ bool WebAssemblyCFGStackify::fixCallUnwindMismatches(MachineFunction &MF) {
!WebAssembly::mayThrow(MI))
continue;
SeenThrowableInstInBB = true;
LLVM_DEBUG(dbgs() << "- fixCallUnwindMismatches considering: " << MI
<< " in MBB = " << MBB.getName() << "\n");

// If the EH pad on the stack top is where this instruction should unwind
// next, we're good.
Expand Down Expand Up @@ -1923,8 +1927,10 @@ bool WebAssemblyCFGStackify::fixCallUnwindMismatches(MachineFunction &MF) {
RecordCallerMismatchRange(EHPadStack.back());

// If EHPadStack is empty, that means it correctly unwinds to the caller
// if it throws, so we're good. If MI does not throw, we're good too.
else if (EHPadStack.empty() || !MayThrow) {
// if it throws, so we're good. A delegate targeting FakeCallerBB also
// correctly unwinds to the caller. If MI does not throw, we're good too.
else if (EHPadStack.empty() || EHPadStack.back() == FakeCallerBB ||
!MayThrow) {
}

// We found an instruction that unwinds to the caller but currently has an
Expand All @@ -1940,6 +1946,8 @@ bool WebAssemblyCFGStackify::fixCallUnwindMismatches(MachineFunction &MF) {
// Update EHPadStack.
if (WebAssembly::isTry(MI.getOpcode()))
EHPadStack.pop_back();
else if (MI.getOpcode() == WebAssembly::DELEGATE)
EHPadStack.push_back(MI.getOperand(0).getMBB());
else if (WebAssembly::isCatch(MI.getOpcode()))
EHPadStack.push_back(MI.getParent());
}
Expand Down Expand Up @@ -2475,8 +2483,11 @@ void WebAssemblyCFGStackify::placeMarkers(MachineFunction &MF) {
// Add an 'unreachable' after 'end_try_table's.
addUnreachableAfterTryTables(MF, TII);
// Fix mismatches in unwind destinations induced by linearizing the code.
fixCallUnwindMismatches(MF);
// Run fixCatchUnwindMismatches() first so that fixCallUnwindMismatches()
// will see and correct any new call/rethrow unwind mismatches introduced by
// fixCatchUnwindMismatches().
fixCatchUnwindMismatches(MF);
fixCallUnwindMismatches(MF);
// addUnreachableAfterTryTables and fixUnwindMismatches create new BBs, so
// we need to recalculate ScopeTops.
recalculateScopeTops(MF);
Expand Down
10 changes: 4 additions & 6 deletions llvm/test/CodeGen/WebAssembly/cfg-stackify-eh-legacy.ll
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Expand Up @@ -659,11 +659,9 @@ try.cont: ; preds = %catch.start0
; --- try-delegate ends (call unwind mismatch)
; NOSORT: catch
; NOSORT: call {{.*}} __cxa_begin_catch
; --- try-delegate starts (call unwind mismatch)
; NOSORT: try
; NOSORT: call __cxa_end_catch
; NOSORT: delegate 3 # label/catch{{[0-9]+}}: to caller
; --- try-delegate ends (call unwind mismatch)
; __cxa_end_catch doesn't need its own try-delegate because the enclosing
; catch-mismatch delegate already routes to caller.
; NOSORT: call __cxa_end_catch
; NOSORT: end_try
; NOSORT: delegate 1 # label/catch{{[0-9]+}}: to caller
; --- try-delegate ends (catch unwind mismatch)
Expand Down Expand Up @@ -1736,7 +1734,7 @@ unreachable: ; preds = %rethrow, %entry
}

; Check if the unwind destination mismatch stats are correct
; NOSORT: 24 wasm-cfg-stackify - Number of call unwind mismatches found
; NOSORT: 23 wasm-cfg-stackify - Number of call unwind mismatches found
; NOSORT: 5 wasm-cfg-stackify - Number of catch unwind mismatches found

declare void @foo()
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
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Expand Up @@ -1507,7 +1507,7 @@ unreachable: ; preds = %rethrow, %entry
}

; Check if the unwind destination mismatch stats are correct
; NOSORT: 23 wasm-cfg-stackify - Number of call unwind mismatches found
; NOSORT: 24 wasm-cfg-stackify - Number of call unwind mismatches found
; NOSORT: 4 wasm-cfg-stackify - Number of catch unwind mismatches found

declare void @foo()
Expand Down
105 changes: 100 additions & 5 deletions llvm/test/CodeGen/WebAssembly/exception-legacy.ll
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Expand Up @@ -429,16 +429,16 @@ unreachable: ; preds = %rethrow
; CHECK: try
; CHECK: try
; CHECK: call __cxa_throw
; CHECK: catch
; CHECK: catch {{.*}} __cpp_exception
; CHECK: call $drop=, __cxa_begin_catch
; CHECK: call __cxa_end_catch
; CHECK: try
; CHECK: try
; Note that this rethrow targets the top-level catch_all
; CHECK: rethrow 4
; CHECK: catch
; CHECK: try
; CHECK: call __cxa_end_catch
; CHECK: delegate 5
; CHECK: catch {{.*}} __cpp_exception
; CHECK: call $drop=, __cxa_begin_catch
; CHECK: call __cxa_end_catch
; CHECK: return
; CHECK: end_try
; CHECK: delegate 3
Expand Down Expand Up @@ -569,6 +569,101 @@ declare void @__cxa_throw(ptr, ptr, ptr) #1
declare void @_ZSt9terminatev()
declare ptr @_ZN4TempD2Ev(ptr returned)

; Regression test for issue #187302: fixCallUnwindMismatches() was run first and
; found that the rethrow had the correct unwind target so did not wrap it in a
; try/delegate. Then fixCatchUnwindMismatches() added a try/delegate for
;
; invoke void @do_catch unwind label %terminate_catchswitch
;
; because otherwise it was going to unwind to outer_catchswitch rather than
; terminate_catchswitch. But this made the rethrow incorrectly transfer control
; to terminate_catchswitch rather than outer_catchswitch.
; Fixed by running fixCatchUnwindMismatches() before fixCallUnwindMismatches().
;
; This pattern occurs in Rust's catch_unwind inside a destructor.

; CHECK-LABEL: catch_unwind_in_cleanup:
; CHECK: catch_all
; CHECK: try
; CHECK: try
; CHECK: call resume_unwind
; CHECK: catch {{.*}} __cpp_exception
; CHECK: call do_catch
; end_cleanup and rethrow are inside the inner catch's scope, but each gets
; its own try-delegate to route exceptions to the correct destination rather
; than going through the catch-mismatch delegate to the terminate handler.
; CHECK: try
; CHECK: call end_cleanup
; CHECK: delegate 7
; (caller)
; CHECK: try
; CHECK: rethrow 7
; (Rethrow exception caught by outermost catch_all)
; CHECK: delegate 2
; (outer_catchswitch)
; CHECK: end_try
; CHECK: delegate 3
; (terminate)
; CHECK: catch {{.*}} __cpp_exception
; CHECK: call do_catch
; CHECK: return
define void @catch_unwind_in_cleanup() personality ptr @__gxx_wasm_personality_v0 {
start:
invoke void @resume_unwind(i32 1)
to label %unreachable unwind label %outer_cleanuppad

outer_cleanuppad:
%outer_pad = cleanuppad within none []
call void @start_cleanup() [ "funclet"(token %outer_pad) ]
invoke void @resume_unwind(i32 2) [ "funclet"(token %outer_pad) ]
to label %unreachable unwind label %inner_catchswitch

inner_catchswitch:
%inner_cs = catchswitch within %outer_pad [label %inner_catchpad] unwind label %terminate_catchswitch

inner_catchpad:
%inner_cp = catchpad within %inner_cs [ptr null]
%exn = call ptr @llvm.wasm.get.exception(token %inner_cp)
%sel = call i32 @llvm.wasm.get.ehselector(token %inner_cp)
invoke void @do_catch(ptr %exn, i32 2) [ "funclet"(token %inner_cp) ]
to label %inner_catchret unwind label %terminate_catchswitch

terminate_catchswitch:
%term_cs = catchswitch within %outer_pad [label %terminate_catchpad] unwind label %outer_catchswitch

terminate_catchpad:
%term_pad = catchpad within %term_cs [ptr null]
call void @panic_in_cleanup() [ "funclet"(token %term_pad) ]
unreachable

inner_catchret:
catchret from %inner_cp to label %outer_cleanupret

outer_cleanupret:
call void @end_cleanup() [ "funclet"(token %outer_pad) ]
cleanupret from %outer_pad unwind label %outer_catchswitch

outer_catchswitch:
%outer_cs = catchswitch within none [label %outer_catchpad] unwind to caller
outer_catchpad:
%outer_cp = catchpad within %outer_cs [ptr null]
%exn2 = call ptr @llvm.wasm.get.exception(token %outer_cp)
%sel2 = call i32 @llvm.wasm.get.ehselector(token %outer_cp)
call void @do_catch(ptr %exn2, i32 1) [ "funclet"(token %outer_cp) ]
catchret from %outer_cp to label %done

done:
ret void
unreachable:
unreachable
}

declare void @resume_unwind(i32) #1
declare void @do_catch(ptr, i32) #0
declare void @start_cleanup()
declare void @end_cleanup()
declare void @panic_in_cleanup() #2

attributes #0 = { nounwind }
attributes #1 = { noreturn }
attributes #2 = { noreturn nounwind }
Expand Down
49 changes: 29 additions & 20 deletions llvm/test/CodeGen/WebAssembly/exception.ll
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Expand Up @@ -484,34 +484,43 @@ unreachable: ; preds = %rethrow
; try_table (catch_all_ref 0)'s caught exception is stored in local 2
; CHECK: local.set 2
; CHECK: block
; catch_all 0 dispatches to %terminate.i
; CHECK: try_table (catch_all 0)
; CHECK: block
; CHECK: block i32
; CHECK: try_table (catch __cpp_exception 0)
; CHECK: call __cxa_throw
; CHECK: block exnref
; CHECK: block
; CHECK: block i32
; CHECK: try_table (catch __cpp_exception 0)
; CHECK: call __cxa_throw
; CHECK: end_try_table
; CHECK: end_block
;
; invoke __cxa_end_catch... unwind label %terminate.i
; should unwind to %terminate.i. catch_all_ref 1 points to the
; try_table (catch_all 0) which in turn dispatches to %terminate.i
; CHECK: try_table (catch_all_ref 1)
; CHECK: call __cxa_end_catch
; CHECK: end_try_table
; CHECK: end_block
; CHECK: call __cxa_end_catch
; CHECK: block i32
; CHECK: try_table (catch_all_ref 5)
; CHECK: try_table (catch __cpp_exception 1)
; CHECK: block i32
; CHECK: try_table (catch_all_ref 6)
; CHECK: try_table (catch __cpp_exception 1)
; Note that the throw_ref below targets the top-level catch_all_ref (local 2)
; CHECK: local.get 2
; CHECK: throw_ref
; CHECK: local.get 2
; CHECK: throw_ref
; CHECK: end_try_table
; CHECK: end_try_table
; CHECK: end_block
; CHECK: try_table (catch_all_ref 5)
; CHECK: call __cxa_end_catch
; CHECK: end_try_table
; CHECK: return
; CHECK: end_block
; CHECK: try_table (catch_all_ref 4)
; CHECK: call __cxa_end_catch
; CHECK: end_try_table
; CHECK: return
; CHECK: end_block
; CHECK: end_try_table
; CHECK: throw_ref
; CHECK: end_try_table
; CHECK: end_block
; CHECK: call _ZSt9terminatev
; CHECK: end_block
; CHECK: call _ZSt9terminatev
; CHECK: end_block
; CHECK: end_block
; CHECK: throw_ref
; CHECK: throw_ref
define void @inlined_cleanupret() personality ptr @__gxx_wasm_personality_v0 {
entry:
%exception = tail call ptr @__cxa_allocate_exception(i32 4)
Expand Down
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