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release/19.x: [WebAssembly] Fix rethrow's index calculation (#114693) #115844

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Nov 19, 2024
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release/19.x: [WebAssembly] Fix rethrow's index calculation (#114693) #115844

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6 changes: 5 additions & 1 deletion llvm/include/llvm/Target/TargetSelectionDAG.td
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Expand Up @@ -231,6 +231,10 @@ def SDTCatchret : SDTypeProfile<0, 2, [ // catchret
SDTCisVT<0, OtherVT>, SDTCisVT<1, OtherVT>
]>;

def SDTCleanupret : SDTypeProfile<0, 1, [ // cleanupret
SDTCisVT<0, OtherVT>
]>;

def SDTNone : SDTypeProfile<0, 0, []>; // ret, trap

def SDTUBSANTrap : SDTypeProfile<0, 1, []>; // ubsantrap
Expand Down Expand Up @@ -680,7 +684,7 @@ def brind : SDNode<"ISD::BRIND" , SDTBrind, [SDNPHasChain]>;
def br : SDNode<"ISD::BR" , SDTBr, [SDNPHasChain]>;
def catchret : SDNode<"ISD::CATCHRET" , SDTCatchret,
[SDNPHasChain, SDNPSideEffect]>;
def cleanupret : SDNode<"ISD::CLEANUPRET" , SDTNone, [SDNPHasChain]>;
def cleanupret : SDNode<"ISD::CLEANUPRET" , SDTCleanupret, [SDNPHasChain]>;

def trap : SDNode<"ISD::TRAP" , SDTNone,
[SDNPHasChain, SDNPSideEffect]>;
Expand Down
6 changes: 4 additions & 2 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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Expand Up @@ -2155,8 +2155,10 @@ void SelectionDAGBuilder::visitCleanupRet(const CleanupReturnInst &I) {
FuncInfo.MBB->normalizeSuccProbs();

// Create the terminator node.
SDValue Ret =
DAG.getNode(ISD::CLEANUPRET, getCurSDLoc(), MVT::Other, getControlRoot());
MachineBasicBlock *CleanupPadMBB =
FuncInfo.MBBMap[I.getCleanupPad()->getParent()];
SDValue Ret = DAG.getNode(ISD::CLEANUPRET, getCurSDLoc(), MVT::Other,
getControlRoot(), DAG.getBasicBlock(CleanupPadMBB));
DAG.setRoot(Ret);
}

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2 changes: 1 addition & 1 deletion llvm/lib/Target/AArch64/AArch64InstrInfo.td
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Expand Up @@ -5159,7 +5159,7 @@ let isPseudo = 1 in {
//===----------------------------------------------------------------------===//
let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
isCodeGenOnly = 1, isReturn = 1, isEHScopeReturn = 1, isPseudo = 1 in {
def CLEANUPRET : Pseudo<(outs), (ins), [(cleanupret)]>, Sched<[]>;
def CLEANUPRET : Pseudo<(outs), (ins), [(cleanupret bb)]>, Sched<[]>;
let usesCustomInserter = 1 in
def CATCHRET : Pseudo<(outs), (ins am_brcond:$dst, am_brcond:$src), [(catchret bb:$dst, bb:$src)]>,
Sched<[]>;
Expand Down
53 changes: 8 additions & 45 deletions llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
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Expand Up @@ -87,9 +87,8 @@ class WebAssemblyCFGStackify final : public MachineFunctionPass {
const MachineBasicBlock *MBB);
unsigned getDelegateDepth(const SmallVectorImpl<EndMarkerInfo> &Stack,
const MachineBasicBlock *MBB);
unsigned
getRethrowDepth(const SmallVectorImpl<EndMarkerInfo> &Stack,
const SmallVectorImpl<const MachineBasicBlock *> &EHPadStack);
unsigned getRethrowDepth(const SmallVectorImpl<EndMarkerInfo> &Stack,
const MachineBasicBlock *EHPadToRethrow);
void rewriteDepthImmediates(MachineFunction &MF);
void fixEndsAtEndOfFunction(MachineFunction &MF);
void cleanupFunctionData(MachineFunction &MF);
Expand Down Expand Up @@ -1612,34 +1611,13 @@ unsigned WebAssemblyCFGStackify::getDelegateDepth(

unsigned WebAssemblyCFGStackify::getRethrowDepth(
const SmallVectorImpl<EndMarkerInfo> &Stack,
const SmallVectorImpl<const MachineBasicBlock *> &EHPadStack) {
const MachineBasicBlock *EHPadToRethrow) {
unsigned Depth = 0;
// In our current implementation, rethrows always rethrow the exception caught
// by the innermost enclosing catch. This means while traversing Stack in the
// reverse direction, when we encounter END_TRY, we should check if the
// END_TRY corresponds to the current innermost EH pad. For example:
// try
// ...
// catch ;; (a)
// try
// rethrow 1 ;; (b)
// catch ;; (c)
// rethrow 0 ;; (d)
// end ;; (e)
// end ;; (f)
//
// When we are at 'rethrow' (d), while reversely traversing Stack the first
// 'end' we encounter is the 'end' (e), which corresponds to the 'catch' (c).
// And 'rethrow' (d) rethrows the exception caught by 'catch' (c), so we stop
// there and the depth should be 0. But when we are at 'rethrow' (b), it
// rethrows the exception caught by 'catch' (a), so when traversing Stack
// reversely, we should skip the 'end' (e) and choose 'end' (f), which
// corresponds to 'catch' (a).
for (auto X : reverse(Stack)) {
const MachineInstr *End = X.second;
if (End->getOpcode() == WebAssembly::END_TRY) {
auto *EHPad = TryToEHPad[EndToBegin[End]];
if (EHPadStack.back() == EHPad)
if (EHPadToRethrow == EHPad)
break;
}
++Depth;
Expand All @@ -1651,7 +1629,6 @@ unsigned WebAssemblyCFGStackify::getRethrowDepth(
void WebAssemblyCFGStackify::rewriteDepthImmediates(MachineFunction &MF) {
// Now rewrite references to basic blocks to be depth immediates.
SmallVector<EndMarkerInfo, 8> Stack;
SmallVector<const MachineBasicBlock *, 8> EHPadStack;
for (auto &MBB : reverse(MF)) {
for (MachineInstr &MI : llvm::reverse(MBB)) {
switch (MI.getOpcode()) {
Expand All @@ -1669,31 +1646,14 @@ void WebAssemblyCFGStackify::rewriteDepthImmediates(MachineFunction &MF) {
break;

case WebAssembly::END_BLOCK:
case WebAssembly::END_TRY:
Stack.push_back(std::make_pair(&MBB, &MI));
break;

case WebAssembly::END_TRY: {
// We handle DELEGATE in the default level, because DELEGATE has
// immediate operands to rewrite.
Stack.push_back(std::make_pair(&MBB, &MI));
auto *EHPad = TryToEHPad[EndToBegin[&MI]];
EHPadStack.push_back(EHPad);
break;
}

case WebAssembly::END_LOOP:
Stack.push_back(std::make_pair(EndToBegin[&MI]->getParent(), &MI));
break;

case WebAssembly::CATCH:
case WebAssembly::CATCH_ALL:
EHPadStack.pop_back();
break;

case WebAssembly::RETHROW:
MI.getOperand(0).setImm(getRethrowDepth(Stack, EHPadStack));
break;

default:
if (MI.isTerminator()) {
// Rewrite MBB operands to be depth immediates.
Expand All @@ -1705,6 +1665,9 @@ void WebAssemblyCFGStackify::rewriteDepthImmediates(MachineFunction &MF) {
if (MI.getOpcode() == WebAssembly::DELEGATE)
MO = MachineOperand::CreateImm(
getDelegateDepth(Stack, MO.getMBB()));
else if (MI.getOpcode() == WebAssembly::RETHROW)
MO = MachineOperand::CreateImm(
getRethrowDepth(Stack, MO.getMBB()));
else
MO = MachineOperand::CreateImm(
getBranchDepth(Stack, MO.getMBB()));
Expand Down
13 changes: 13 additions & 0 deletions llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
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Expand Up @@ -245,6 +245,19 @@ void WebAssemblyDAGToDAGISel::Select(SDNode *Node) {
ReplaceNode(Node, Throw);
return;
}
case Intrinsic::wasm_rethrow: {
// RETHROW's BB argument will be populated in LateEHPrepare. Just use a
// '0' as a placeholder for now.
MachineSDNode *Rethrow = CurDAG->getMachineNode(
WebAssembly::RETHROW, DL,
MVT::Other, // outchain type
{
CurDAG->getConstant(0, DL, MVT::i32), // placeholder
Node->getOperand(0) // inchain
});
ReplaceNode(Node, Rethrow);
return;
}
}
break;
}
Expand Down
9 changes: 4 additions & 5 deletions llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td
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Expand Up @@ -132,11 +132,9 @@ let isTerminator = 1, hasCtrlDep = 1, isBarrier = 1 in {
defm THROW : I<(outs), (ins tag_op:$tag, variable_ops),
(outs), (ins tag_op:$tag), [],
"throw \t$tag", "throw \t$tag", 0x08>;
defm RETHROW : NRI<(outs), (ins i32imm:$depth), [], "rethrow \t$depth", 0x09>;
// $ehpad is the EH pad where the exception to rethrow has been caught.
defm RETHROW : NRI<(outs), (ins bb_op:$ehpad), [], "rethrow \t$ehpad", 0x09>;
} // isTerminator = 1, hasCtrlDep = 1, isBarrier = 1
// The depth argument will be computed in CFGStackify. We set it to 0 here for
// now.
def : Pat<(int_wasm_rethrow), (RETHROW 0)>;

// Region within which an exception is caught: try / end_try
let Uses = [VALUE_STACK], Defs = [VALUE_STACK] in {
Expand All @@ -160,7 +158,8 @@ defm DELEGATE : NRI<(outs), (ins bb_op:$dst), [], "delegate \t $dst", 0x18>;
// Pseudo instructions: cleanupret / catchret
let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
isPseudo = 1, isEHScopeReturn = 1 in {
defm CLEANUPRET : NRI<(outs), (ins), [(cleanupret)], "cleanupret", 0>;
defm CLEANUPRET : NRI<(outs), (ins bb_op:$ehpad), [(cleanupret bb:$ehpad)],
"cleanupret", 0>;
defm CATCHRET : NRI<(outs), (ins bb_op:$dst, bb_op:$from),
[(catchret bb:$dst, bb:$from)], "catchret", 0>;
} // isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
Expand Down
34 changes: 31 additions & 3 deletions llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
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Expand Up @@ -245,11 +245,39 @@ bool WebAssemblyLateEHPrepare::replaceFuncletReturns(MachineFunction &MF) {
Changed = true;
break;
}
case WebAssembly::RETHROW:
// These RETHROWs here were lowered from llvm.wasm.rethrow() intrinsics,
// generated in Clang for when an exception is not caught by the given
// type (e.g. catch (int)).
//
// RETHROW's BB argument is the EH pad where the exception to rethrow has
// been caught. (Until this point, RETHROW has just a '0' as a placeholder
// argument.) For these llvm.wasm.rethrow()s, we can safely assume the
// exception comes from the nearest dominating EH pad, because catch.start
// EH pad is structured like this:
//
// catch.start:
// catchpad ...
// %matches = compare ehselector with typeid
// br i1 %matches, label %catch, label %rethrow
//
// rethrow:
// ;; rethrows the exception caught in 'catch.start'
// call @llvm.wasm.rethrow()
TI->removeOperand(0);
TI->addOperand(MachineOperand::CreateMBB(getMatchingEHPad(TI)));
Changed = true;
break;
case WebAssembly::CLEANUPRET: {
// Replace a cleanupret with a rethrow. For C++ support, currently
// rethrow's immediate argument is always 0 (= the latest exception).
// CLEANUPRETs have the EH pad BB the exception to rethrow has been caught
// as an argument. Use it and change the instruction opcode to 'RETHROW'
// to make rethrowing instructions consistent.
//
// This is because we cannot safely assume that it is always the nearest
// dominating EH pad, in case there are code transformations such as
// inlining.
BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW))
.addImm(0);
.addMBB(TI->getOperand(0).getMBB());
TI->eraseFromParent();
Changed = true;
break;
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/Target/X86/X86InstrCompiler.td
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Expand Up @@ -195,7 +195,8 @@ def EH_RETURN64 : I<0xC3, RawFrm, (outs), (ins GR64:$addr),

let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
isCodeGenOnly = 1, isReturn = 1, isEHScopeReturn = 1 in {
def CLEANUPRET : I<0, Pseudo, (outs), (ins), "# CLEANUPRET", [(cleanupret)]>;
def CLEANUPRET : I<0, Pseudo, (outs), (ins), "# CLEANUPRET",
[(cleanupret bb)]>;

// CATCHRET needs a custom inserter for SEH.
let usesCustomInserter = 1 in
Expand Down
11 changes: 7 additions & 4 deletions llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.mir
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Expand Up @@ -39,15 +39,16 @@ body: |
; CHECK: RETHROW 1
EH_LABEL <mcsymbol .Ltmp2>
%0:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
RETHROW 0, implicit-def dead $arguments
RETHROW %bb.1, implicit-def dead $arguments

bb.2 (landing-pad):
successors: %bb.3
; CHECK: bb.2 (landing-pad):
; CHECK: CATCH
; CHECK: RETHROW 0
EH_LABEL <mcsymbol .Ltmp3>
%1:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
RETHROW 0, implicit-def dead $arguments
RETHROW %bb.2, implicit-def dead $arguments

bb.3:
; CHECK: bb.3:
Expand Down Expand Up @@ -104,12 +105,14 @@ body: |
RETURN %0:i32, implicit-def dead $arguments

bb.3 (landing-pad):
successors:
EH_LABEL <mcsymbol .Ltmp4>
%0:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
RETHROW 0, implicit-def dead $arguments
RETHROW %bb.3, implicit-def dead $arguments

bb.4 (landing-pad):
successors:
EH_LABEL <mcsymbol .Ltmp5>
%1:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
RETHROW 0, implicit-def dead $arguments
RETHROW %bb.4, implicit-def dead $arguments
...
105 changes: 105 additions & 0 deletions llvm/test/CodeGen/WebAssembly/exception-legacy.ll
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Expand Up @@ -400,6 +400,107 @@ unreachable: ; preds = %rethrow
unreachable
}

; The bitcode below is generated when the code below is compiled and
; Temp::~Temp() is inlined into inlined_cleanupret():
;
; void inlined_cleanupret() {
; try {
; Temp t;
; throw 2;
; } catch (...)
; }
;
; Temp::~Temp() {
; try {
; throw 1;
; } catch (...) {
; }
; }
;
; ~Temp() generates cleanupret, which is lowered to a 'rethrow' later. That
; rethrow's immediate argument should correctly target the top-level cleanuppad
; (catch_all). This is a regression test for the bug where we did not compute
; rethrow's argument correctly.

; CHECK-LABEL: inlined_cleanupret:
; CHECK: try
; CHECK: call __cxa_throw
; CHECK: catch_all
; CHECK: try
; CHECK: try
; CHECK: call __cxa_throw
; CHECK: 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: return
; CHECK: end_try
; CHECK: delegate 3
; CHECK: end_try
; CHECK: catch_all
; CHECK: call _ZSt9terminatev
; CHECK: end_try
; CHECK: end_try
define void @inlined_cleanupret() personality ptr @__gxx_wasm_personality_v0 {
entry:
%exception = tail call ptr @__cxa_allocate_exception(i32 4)
store i32 2, ptr %exception, align 16
invoke void @__cxa_throw(ptr nonnull %exception, ptr nonnull @_ZTIi, ptr null)
to label %unreachable unwind label %ehcleanup

ehcleanup: ; preds = %entry
%0 = cleanuppad within none []
%exception.i = call ptr @__cxa_allocate_exception(i32 4) [ "funclet"(token %0) ]
store i32 1, ptr %exception.i, align 16
invoke void @__cxa_throw(ptr nonnull %exception.i, ptr nonnull @_ZTIi, ptr null) [ "funclet"(token %0) ]
to label %unreachable unwind label %catch.dispatch.i

catch.dispatch.i: ; preds = %ehcleanup
%1 = catchswitch within %0 [label %catch.start.i] unwind label %terminate.i

catch.start.i: ; preds = %catch.dispatch.i
%2 = catchpad within %1 [ptr null]
%3 = tail call ptr @llvm.wasm.get.exception(token %2)
%4 = tail call i32 @llvm.wasm.get.ehselector(token %2)
%5 = call ptr @__cxa_begin_catch(ptr %3) [ "funclet"(token %2) ]
invoke void @__cxa_end_catch() [ "funclet"(token %2) ]
to label %invoke.cont.i unwind label %terminate.i

invoke.cont.i: ; preds = %catch.start.i
catchret from %2 to label %_ZN4TempD2Ev.exit

terminate.i: ; preds = %catch.start.i, %catch.dispatch.i
%6 = cleanuppad within %0 []
call void @_ZSt9terminatev() [ "funclet"(token %6) ]
unreachable

_ZN4TempD2Ev.exit: ; preds = %invoke.cont.i
cleanupret from %0 unwind label %catch.dispatch

catch.dispatch: ; preds = %_ZN4TempD2Ev.exit
%7 = catchswitch within none [label %catch.start] unwind to caller

catch.start: ; preds = %catch.dispatch
%8 = catchpad within %7 [ptr null]
%9 = tail call ptr @llvm.wasm.get.exception(token %8)
%10 = tail call i32 @llvm.wasm.get.ehselector(token %8)
%11 = call ptr @__cxa_begin_catch(ptr %9) #8 [ "funclet"(token %8) ]
call void @__cxa_end_catch() [ "funclet"(token %8) ]
catchret from %8 to label %try.cont

try.cont: ; preds = %catch.start
ret void

unreachable: ; preds = %entry
unreachable
}


declare void @foo()
declare void @bar(ptr)
Expand All @@ -415,8 +516,12 @@ declare i32 @llvm.wasm.get.ehselector(token) #0
declare void @llvm.wasm.rethrow() #1
; Function Attrs: nounwind
declare i32 @llvm.eh.typeid.for(ptr) #0
; Function Attrs: nounwind
declare ptr @__cxa_allocate_exception(i32) #0
declare ptr @__cxa_begin_catch(ptr)
declare void @__cxa_end_catch()
; Function Attrs: noreturn
declare void @__cxa_throw(ptr, ptr, ptr) #1
declare void @_ZSt9terminatev()
declare ptr @_ZN4TempD2Ev(ptr returned)

Expand Down
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