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[WebAssembly] Treat 'rethrow' as terminator in custom isel #95967

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Jun 19, 2024
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[WebAssembly] Treat 'rethrow' as terminator in custom isel #95967

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2 changes: 1 addition & 1 deletion llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3355,7 +3355,7 @@ void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
// special because it can be invoked, so we manually lower it to a DAG
// node here.
SmallVector<SDValue, 8> Ops;
Ops.push_back(getRoot()); // inchain
Ops.push_back(getControlRoot()); // inchain for the terminator node
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
Ops.push_back(
DAG.getTargetConstant(Intrinsic::wasm_rethrow, getCurSDLoc(),
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52 changes: 52 additions & 0 deletions llvm/test/CodeGen/WebAssembly/exception-legacy.ll
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Expand Up @@ -350,8 +350,60 @@ ehcleanupret: ; preds = %catch.start, %ehcle
cleanupret from %0 unwind to caller
}

; Regression test for the bug that 'rethrow' was not treated correctly as a
; terminator in isel.
define void @test_rethrow_terminator() personality ptr @__gxx_wasm_personality_v0 {
entry:
invoke void @foo()
to label %try.cont unwind label %catch.dispatch

catch.dispatch: ; preds = %entry
%0 = catchswitch within none [label %catch.start] unwind label %ehcleanup

catch.start: ; preds = %catch.dispatch
%1 = catchpad within %0 [ptr @_ZTIi]
%2 = call ptr @llvm.wasm.get.exception(token %1)
%3 = call i32 @llvm.wasm.get.ehselector(token %1)
%4 = call i32 @llvm.eh.typeid.for.p0(ptr @_ZTIi)
%matches = icmp eq i32 %3, %4
br i1 %matches, label %catch, label %rethrow

catch: ; preds = %catch.start
%5 = call ptr @__cxa_begin_catch(ptr %2) [ "funclet"(token %1) ]
%6 = load i32, ptr %5, align 4
call void @__cxa_end_catch() [ "funclet"(token %1) ]
catchret from %1 to label %try.cont

rethrow: ; preds = %catch.start
invoke void @llvm.wasm.rethrow() #1 [ "funclet"(token %1) ]
to label %unreachable unwind label %ehcleanup

try.cont: ; preds = %entry, %catch
ret void

ehcleanup: ; preds = %rethrow, %catch.dispatch
; 'rethrow' BB is this BB's predecessor, and its
; 'invoke void @llvm.wasm.rethrow()' is lowered down to a 'RETHROW' in Wasm
; MIR. And this 'phi' creates 'CONST_I32' instruction in the predecessor
; 'rethrow' BB. If 'RETHROW' is not treated correctly as a terminator, it can
; create a BB like
; bb.3.rethrow:
; RETHROW 0
; %0 = CONST_I32 20
; BR ...
%tmp = phi i32 [ 10, %catch.dispatch ], [ 20, %rethrow ]
%7 = cleanuppad within none []
call void @take_i32(i32 %tmp) [ "funclet"(token %7) ]
cleanupret from %7 unwind to caller

unreachable: ; preds = %rethrow
unreachable
}


declare void @foo()
declare void @bar(ptr)
declare void @take_i32(i32)
declare i32 @__gxx_wasm_personality_v0(...)
; Function Attrs: noreturn
declare void @llvm.wasm.throw(i32, ptr) #1
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