[llvm] 2b957ed - [WebAssembly] Fix ExceptionInfo grouping again
Heejin Ahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 4 15:06:02 PST 2021
Author: Heejin Ahn
Date: 2021-03-04T15:05:13-08:00
New Revision: 2b957ed4ff3344d8f761a053566e307277a1cdeb
URL: https://github.com/llvm/llvm-project/commit/2b957ed4ff3344d8f761a053566e307277a1cdeb
DIFF: https://github.com/llvm/llvm-project/commit/2b957ed4ff3344d8f761a053566e307277a1cdeb.diff
LOG: [WebAssembly] Fix ExceptionInfo grouping again
This is a case D97677 missed. When taking out remaining BBs that are
reachable from already-taken-out exceptions (because they are not
subexcptions but unwind destinations), I assumed the remaining BBs are
not EH pads, but they can be. For example,
```
try {
try {
throw 0;
} catch (int) { // (a)
}
} catch (int) { // (b)
}
try {
foo();
} catch (int) { // (c)
}
```
In this code, (b) is the unwind destination of (a) so its exception is
taken out of (a)'s exception, But even though the next try-catch is not
inside the first two-level try-catches, because the first try always
throws, its continuation BB is unreachable and the whole rest of the
function is dominated by EH pad (a), including EH pad (c). So after we
take out of (b)'s exception out of (a)'s, we also need to take out (c)'s
exception out of (a)'s, because (c) is reachable from (b).
This adds one more step before what we did for remaining BBs in D97677;
it traverses EH pads first to take subexceptions out of their incorrect
parent exception. It's the same thing as D97677, but because we can do
this before we add BBs to exceptions' sets, we don't need to fix sets
and only need to fix parent exception pointers.
Other changes are variable name changes (I changed `WE` -> `SrcWE`,
`UnwindWE` -> `DstWE` for clarity), some comment changes, and a drive-by
fix in a bug in a `LLVM_DEBUG` print statement.
Fixes https://github.com/emscripten-core/emscripten/issues/13588.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D97929
Added:
Modified:
llvm/lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp
llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp
index 5cfc872eac10..4328fd36cbe4 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExceptionInfo.cpp
@@ -120,7 +120,8 @@ void WebAssemblyExceptionInfo::recalculate(
// and A's unwind destination is B and B's is C. When we visit B before A, we
// end up extracting C only out of B but not out of A.
const auto *EHInfo = MF.getWasmEHFuncInfo();
- DenseMap<WebAssemblyException *, WebAssemblyException *> UnwindWEMap;
+ SmallVector<std::pair<WebAssemblyException *, WebAssemblyException *>>
+ UnwindWEVec;
for (auto *DomNode : depth_first(&MDT)) {
MachineBasicBlock *EHPad = DomNode->getBlock();
if (!EHPad->isEHPad())
@@ -128,30 +129,20 @@ void WebAssemblyExceptionInfo::recalculate(
if (!EHInfo->hasUnwindDest(EHPad))
continue;
auto *UnwindDest = EHInfo->getUnwindDest(EHPad);
- auto *WE = getExceptionFor(EHPad);
- auto *UnwindWE = getExceptionFor(UnwindDest);
- if (WE->contains(UnwindWE)) {
- UnwindWEMap[WE] = UnwindWE;
- LLVM_DEBUG(dbgs() << "ExceptionInfo fix: " << WE->getEHPad()->getNumber()
- << "." << WE->getEHPad()->getName()
+ auto *SrcWE = getExceptionFor(EHPad);
+ auto *DstWE = getExceptionFor(UnwindDest);
+ if (SrcWE->contains(DstWE)) {
+ UnwindWEVec.push_back(std::make_pair(SrcWE, DstWE));
+ LLVM_DEBUG(dbgs() << "Unwind destination ExceptionInfo fix:\n "
+ << DstWE->getEHPad()->getNumber() << "."
+ << DstWE->getEHPad()->getName()
<< "'s exception is taken out of "
- << UnwindWE->getEHPad()->getNumber() << "."
- << UnwindWE->getEHPad()->getName() << "'s exception\n");
- if (WE->getParentException())
- UnwindWE->setParentException(WE->getParentException());
- else
- UnwindWE->setParentException(nullptr);
+ << SrcWE->getEHPad()->getNumber() << "."
+ << SrcWE->getEHPad()->getName() << "'s exception\n");
+ DstWE->setParentException(SrcWE->getParentException());
}
}
- // Add BBs to exceptions' block set first
- for (auto *DomNode : post_order(&MDT)) {
- MachineBasicBlock *MBB = DomNode->getBlock();
- WebAssemblyException *WE = getExceptionFor(MBB);
- for (; WE; WE = WE->getParentException())
- WE->addToBlocksSet(MBB);
- }
-
// After fixing subexception relationship between unwind destinations above,
// there can still be remaining discrepancies.
//
@@ -161,31 +152,72 @@ void WebAssemblyExceptionInfo::recalculate(
// subexception of Exception A, and we fix it by taking Exception B out of
// Exception A above. But there can still be remaining BBs within Exception A
// that are reachable from Exception B. These BBs semantically don't belong
- // to Exception A and were not a part of 'catch' clause or cleanup code in the
- // original code, but they just happened to be grouped within Exception A
- // because they were dominated by EHPad A. We fix this case by taking those
+ // to Exception A and were not a part of this 'catch' clause or cleanup code
+ // in the original code, but they just happened to be grouped within Exception
+ // A because they were dominated by EHPad A. We fix this case by taking those
// BBs out of the incorrect exception and all its subexceptions that it
// belongs to.
- for (auto &KV : UnwindWEMap) {
- WebAssemblyException *WE = KV.first;
- WebAssemblyException *UnwindWE = KV.second;
+ //
+ // 1. First, we take out remaining incorrect subexceptions. This part is
+ // easier, because we haven't added BBs to exceptions yet, we only need to
+ // change parent exception pointer.
+ for (auto *DomNode : depth_first(&MDT)) {
+ MachineBasicBlock *EHPad = DomNode->getBlock();
+ if (!EHPad->isEHPad())
+ continue;
+ auto *WE = getExceptionFor(EHPad);
+
+ // For each source EHPad -> unwind destination EHPad
+ for (auto &P : UnwindWEVec) {
+ auto *SrcWE = P.first;
+ auto *DstWE = P.second;
+ // If WE (the current EH pad's exception) is still contained in SrcWE but
+ // reachable from DstWE that was taken out of SrcWE above, we have to take
+ // out WE out of SrcWE too.
+ if (WE != SrcWE && SrcWE->contains(WE) && !DstWE->contains(WE) &&
+ isReachableAmongDominated(DstWE->getEHPad(), EHPad, SrcWE->getEHPad(),
+ MDT)) {
+ LLVM_DEBUG(dbgs() << "Remaining reachable ExceptionInfo fix:\n "
+ << WE->getEHPad()->getNumber() << "."
+ << WE->getEHPad()->getName()
+ << "'s exception is taken out of "
+ << SrcWE->getEHPad()->getNumber() << "."
+ << SrcWE->getEHPad()->getName() << "'s exception\n");
+ WE->setParentException(SrcWE->getParentException());
+ }
+ }
+ }
+
+ // Add BBs to exceptions' block set. This is a preparation to take out
+ // remaining incorect BBs from exceptions, because we need to iterate over BBs
+ // for each exception.
+ for (auto *DomNode : post_order(&MDT)) {
+ MachineBasicBlock *MBB = DomNode->getBlock();
+ WebAssemblyException *WE = getExceptionFor(MBB);
+ for (; WE; WE = WE->getParentException())
+ WE->addToBlocksSet(MBB);
+ }
+
+ // 2. We take out remaining individual BBs out. Now we have added BBs to each
+ // exceptions' BlockSet, when we take a BB out of an exception, we need to fix
+ // those sets too.
+ for (auto &P : UnwindWEVec) {
+ auto *SrcWE = P.first;
+ auto *DstWE = P.second;
- for (auto *MBB : WE->getBlocksSet()) {
+ for (auto *MBB : SrcWE->getBlocksSet()) {
if (MBB->isEHPad()) {
- // If this assertion is triggered, it would be a violation of scoping
- // rules in ll files, because this means an instruction in an outer
- // scope tries to unwind to an EH pad in an inner scope.
- assert(!isReachableAmongDominated(UnwindWE->getEHPad(), MBB,
- WE->getEHPad(), MDT) &&
- "Outer scope unwinds to inner scope. Bug in scope rules?");
+ assert(!isReachableAmongDominated(DstWE->getEHPad(), MBB,
+ SrcWE->getEHPad(), MDT) &&
+ "We already handled EH pads above");
continue;
}
- if (isReachableAmongDominated(UnwindWE->getEHPad(), MBB, WE->getEHPad(),
+ if (isReachableAmongDominated(DstWE->getEHPad(), MBB, SrcWE->getEHPad(),
MDT)) {
LLVM_DEBUG(dbgs() << "Remainder BB: " << MBB->getNumber() << "."
- << MBB->getName() << " is ");
+ << MBB->getName() << " is\n");
WebAssemblyException *InnerWE = getExceptionFor(MBB);
- while (InnerWE != WE) {
+ while (InnerWE != SrcWE) {
LLVM_DEBUG(dbgs()
<< " removed from " << InnerWE->getEHPad()->getNumber()
<< "." << InnerWE->getEHPad()->getName()
@@ -193,13 +225,13 @@ void WebAssemblyExceptionInfo::recalculate(
InnerWE->removeFromBlocksSet(MBB);
InnerWE = InnerWE->getParentException();
}
- WE->removeFromBlocksSet(MBB);
- LLVM_DEBUG(dbgs() << " removed from " << WE->getEHPad()->getNumber()
- << "." << WE->getEHPad()->getName()
+ SrcWE->removeFromBlocksSet(MBB);
+ LLVM_DEBUG(dbgs() << " removed from " << SrcWE->getEHPad()->getNumber()
+ << "." << SrcWE->getEHPad()->getName()
<< "'s exception\n");
- changeExceptionFor(MBB, WE->getParentException());
- if (WE->getParentException())
- WE->getParentException()->addToBlocksSet(MBB);
+ changeExceptionFor(MBB, SrcWE->getParentException());
+ if (SrcWE->getParentException())
+ SrcWE->getParentException()->addToBlocksSet(MBB);
}
}
}
diff --git a/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll b/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
index c18e2389e808..3e7ef1b3c29e 100644
--- a/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
+++ b/llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
@@ -1537,6 +1537,111 @@ unreachable: ; preds = %rethrow, %rethrow6
unreachable
}
+; void test25() {
+; try {
+; try {
+; throw 0;
+; } catch (int) { // (a)
+; }
+; } catch (int) { // (b)
+; }
+; try {
+; foo();
+; } catch (int) { // (c)
+; }
+; }
+;
+; Regression test for an ExceptionInfo grouping bug. Because the first (inner)
+; try always throws, both EH pads (b) (catch.start2) and (c) (catch.start10) are
+; dominated by EH pad (a) (catch.start), even though they are not semantically
+; contained in (a)'s exception. Because (a)'s unwind destination is (b), (b)'s
+; exception is taken out of (a)'s. But because (c) is reachable from (b), we
+; should make sure to take out (c)'s exception out of (a)'s exception too.
+define void @test25() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+entry:
+ %exception = call i8* @__cxa_allocate_exception(i32 4) #1
+ %0 = bitcast i8* %exception to i32*
+ store i32 0, i32* %0, align 16
+ invoke void @__cxa_throw(i8* %exception, i8* bitcast (i8** @_ZTIi to i8*), i8* null) #3
+ to label %unreachable unwind label %catch.dispatch
+
+catch.dispatch: ; preds = %entry
+ %1 = catchswitch within none [label %catch.start] unwind label %catch.dispatch1
+
+catch.start: ; preds = %catch.dispatch
+ %2 = catchpad within %1 [i8* bitcast (i8** @_ZTIi to i8*)]
+ %3 = call i8* @llvm.wasm.get.exception(token %2)
+ %4 = call i32 @llvm.wasm.get.ehselector(token %2)
+ %5 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) #1
+ %matches = icmp eq i32 %4, %5
+ br i1 %matches, label %catch, label %rethrow
+
+catch: ; preds = %catch.start
+ %6 = call i8* @__cxa_begin_catch(i8* %3) #1 [ "funclet"(token %2) ]
+ %7 = bitcast i8* %6 to i32*
+ %8 = load i32, i32* %7, align 4
+ call void @__cxa_end_catch() #1 [ "funclet"(token %2) ]
+ catchret from %2 to label %try.cont8
+
+rethrow: ; preds = %catch.start
+ invoke void @llvm.wasm.rethrow() #3 [ "funclet"(token %2) ]
+ to label %unreachable unwind label %catch.dispatch1
+
+catch.dispatch1: ; preds = %rethrow, %catch.dispatch
+ %9 = catchswitch within none [label %catch.start2] unwind to caller
+
+catch.start2: ; preds = %catch.dispatch1
+ %10 = catchpad within %9 [i8* bitcast (i8** @_ZTIi to i8*)]
+ %11 = call i8* @llvm.wasm.get.exception(token %10)
+ %12 = call i32 @llvm.wasm.get.ehselector(token %10)
+ %13 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) #1
+ %matches3 = icmp eq i32 %12, %13
+ br i1 %matches3, label %catch5, label %rethrow4
+
+catch5: ; preds = %catch.start2
+ %14 = call i8* @__cxa_begin_catch(i8* %11) #1 [ "funclet"(token %10) ]
+ %15 = bitcast i8* %14 to i32*
+ %16 = load i32, i32* %15, align 4
+ call void @__cxa_end_catch() #1 [ "funclet"(token %10) ]
+ catchret from %10 to label %try.cont8
+
+rethrow4: ; preds = %catch.start2
+ call void @llvm.wasm.rethrow() #3 [ "funclet"(token %10) ]
+ unreachable
+
+try.cont8: ; preds = %catch, %catch5
+ invoke void @foo()
+ to label %try.cont16 unwind label %catch.dispatch9
+
+catch.dispatch9: ; preds = %try.cont8
+ %17 = catchswitch within none [label %catch.start10] unwind to caller
+
+catch.start10: ; preds = %catch.dispatch9
+ %18 = catchpad within %17 [i8* bitcast (i8** @_ZTIi to i8*)]
+ %19 = call i8* @llvm.wasm.get.exception(token %18)
+ %20 = call i32 @llvm.wasm.get.ehselector(token %18)
+ %21 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) #1
+ %matches11 = icmp eq i32 %20, %21
+ br i1 %matches11, label %catch13, label %rethrow12
+
+catch13: ; preds = %catch.start10
+ %22 = call i8* @__cxa_begin_catch(i8* %19) #1 [ "funclet"(token %18) ]
+ %23 = bitcast i8* %22 to i32*
+ %24 = load i32, i32* %23, align 4
+ call void @__cxa_end_catch() #1 [ "funclet"(token %18) ]
+ catchret from %18 to label %try.cont16
+
+rethrow12: ; preds = %catch.start10
+ call void @llvm.wasm.rethrow() #3 [ "funclet"(token %18) ]
+ unreachable
+
+try.cont16: ; preds = %try.cont8, %catch13
+ ret void
+
+unreachable: ; preds = %rethrow, %entry
+ unreachable
+}
+
; Check if the unwind destination mismatch stats are correct
; NOSORT: 23 wasm-cfg-stackify - Number of call unwind mismatches found
; NOSORT: 4 wasm-cfg-stackify - Number of catch unwind mismatches found
More information about the llvm-commits
mailing list