[WebAssemblyLowerEmscriptenEHSjLj] Avoid lifetime of phi #150932
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
After llvm#149310 lifetime intrinsics require an alloca argument, an invariant that this pass can break. I've fixed this in two ways: * First, move static allocas into the entry block. Currently, the way the pass splits the entry block makes all allocas dynamic, which I assume was not actually intended. This will avoid unnecessary SSA reconstruction for allocas as well, and thus avoid the problem. * If this fails (for dynamic allocas) drop all lifetime intrinsics if any one of them would require a rewrite during SSA reconstruction. Fixes llvm#150498.
|
@llvm/pr-subscribers-backend-webassembly Author: Nikita Popov (nikic) ChangesAfter #149310 lifetime intrinsics require an alloca argument, an invariant that this pass can break. I've fixed this in two ways:
Fixes #150498. Full diff: https://github.com/llvm/llvm-project/pull/150932.diff 6 Files Affected:
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
index 28f65990120cb..c3990d12f2c28 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
@@ -782,6 +782,24 @@ void WebAssemblyLowerEmscriptenEHSjLj::rebuildSSA(Function &F) {
for (Instruction &I : BB) {
if (I.getType()->isVoidTy())
continue;
+
+ if (isa<AllocaInst>(&I)) {
+ // If the alloca has any lifetime marker that is no longer dominated
+ // by the alloca, remove all lifetime markers. Lifetime markers must
+ // always work directly on the alloca, and this is no longer possible.
+ bool HasNonDominatedLifetimeMarker = any_of(I.users(), [&](User *U) {
+ auto *UserI = cast<Instruction>(U);
+ return UserI->isLifetimeStartOrEnd() && !DT.dominates(&I, UserI);
+ });
+ if (HasNonDominatedLifetimeMarker) {
+ for (User *U : make_early_inc_range(I.users())) {
+ auto *UserI = cast<Instruction>(U);
+ if (UserI->isLifetimeStartOrEnd())
+ UserI->eraseFromParent();
+ }
+ }
+ }
+
unsigned VarID = SSA.AddVariable(I.getName(), I.getType());
// If a value is defined by an invoke instruction, it is only available in
// its normal destination and not in its unwind destination.
@@ -1269,10 +1287,20 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
// Setjmp preparation
+ SmallVector<AllocaInst *> StaticAllocas;
+ for (Instruction &I : F.getEntryBlock())
+ if (auto *AI = dyn_cast<AllocaInst>(&I))
+ if (AI->isStaticAlloca())
+ StaticAllocas.push_back(AI);
+
BasicBlock *Entry = &F.getEntryBlock();
DebugLoc FirstDL = getOrCreateDebugLoc(&*Entry->begin(), F.getSubprogram());
SplitBlock(Entry, &*Entry->getFirstInsertionPt());
+ // Move static allocas back into the entry block, so they stay static.
+ for (AllocaInst *AI : StaticAllocas)
+ AI->moveBefore(Entry->getTerminator()->getIterator());
+
IRB.SetInsertPoint(Entry->getTerminator()->getIterator());
// This alloca'ed pointer is used by the runtime to identify function
// invocations. It's just for pointer comparisons. It will never be
diff --git a/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-alloca.ll b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-alloca.ll
new file mode 100644
index 0000000000000..0f968de8a7344
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-alloca.ll
@@ -0,0 +1,129 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -wasm-lower-em-ehsjlj -wasm-enable-sjlj -mtriple=wasm32-unknown-emscripten < %s | FileCheck %s
+
+@buf = external global i8
+declare i32 @setjmp(ptr) returns_twice
+declare void @dummy()
+
+define void @test_static() {
+; CHECK-LABEL: define void @test_static() personality ptr @__gxx_wasm_personality_v0 {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: [[X:%.*]] = alloca i32, align 4
+; CHECK-NEXT: [[FUNCTIONINVOCATIONID:%.*]] = alloca i32, align 4
+; CHECK-NEXT: br label %[[SETJMP_DISPATCH:.*]]
+; CHECK: [[SETJMP_DISPATCH]]:
+; CHECK-NEXT: [[VAL1:%.*]] = phi i32 [ [[VAL:%.*]], %[[IF_END:.*]] ], [ undef, %[[ENTRY]] ]
+; CHECK-NEXT: [[LABEL_PHI:%.*]] = phi i32 [ [[LABEL:%.*]], %[[IF_END]] ], [ -1, %[[ENTRY]] ]
+; CHECK-NEXT: switch i32 [[LABEL_PHI]], label %[[ENTRY_SPLIT:.*]] [
+; CHECK-NEXT: i32 1, label %[[ENTRY_SPLIT_SPLIT:.*]]
+; CHECK-NEXT: ]
+; CHECK: [[ENTRY_SPLIT]]:
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr [[X]])
+; CHECK-NEXT: call void @__wasm_setjmp(ptr @buf, i32 1, ptr [[FUNCTIONINVOCATIONID]])
+; CHECK-NEXT: br label %[[ENTRY_SPLIT_SPLIT]]
+; CHECK: [[ENTRY_SPLIT_SPLIT]]:
+; CHECK-NEXT: [[SETJMP_RET:%.*]] = phi i32 [ 0, %[[ENTRY_SPLIT]] ], [ [[VAL1]], %[[SETJMP_DISPATCH]] ]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[SETJMP_RET]], 0
+; CHECK-NEXT: br i1 [[CMP]], label %[[IF:.*]], label %[[ELSE:.*]]
+; CHECK: [[IF]]:
+; CHECK-NEXT: invoke void @dummy()
+; CHECK-NEXT: to [[DOTNOEXC:label %.*]] unwind label %[[CATCH_DISPATCH_LONGJMP:.*]]
+; CHECK: [[_NOEXC:.*:]]
+; CHECK-NEXT: ret void
+; CHECK: [[ELSE]]:
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr [[X]])
+; CHECK-NEXT: ret void
+; CHECK: [[CATCH_DISPATCH_LONGJMP]]:
+; CHECK-NEXT: [[TMP0:%.*]] = catchswitch within none [label %catch.longjmp] unwind to caller
+; CHECK: [[CATCH_LONGJMP:.*:]]
+; CHECK-NEXT: [[TMP1:%.*]] = catchpad within [[TMP0]] []
+; CHECK-NEXT: [[THROWN:%.*]] = call ptr @llvm.wasm.catch(i32 1)
+; CHECK-NEXT: [[ENV_GEP:%.*]] = getelementptr { ptr, i32 }, ptr [[THROWN]], i32 0, i32 0
+; CHECK-NEXT: [[VAL_GEP:%.*]] = getelementptr { ptr, i32 }, ptr [[THROWN]], i32 0, i32 1
+; CHECK-NEXT: [[ENV:%.*]] = load ptr, ptr [[ENV_GEP]], align 4
+; CHECK-NEXT: [[VAL]] = load i32, ptr [[VAL_GEP]], align 4
+; CHECK-NEXT: [[LABEL]] = call i32 @__wasm_setjmp_test(ptr [[ENV]], ptr [[FUNCTIONINVOCATIONID]]) [ "funclet"(token [[TMP1]]) ]
+; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[LABEL]], 0
+; CHECK-NEXT: br i1 [[TMP2]], label %[[IF_THEN:.*]], label %[[IF_END]]
+; CHECK: [[IF_THEN]]:
+; CHECK-NEXT: call void @__wasm_longjmp(ptr [[ENV]], i32 [[VAL]]) [ "funclet"(token [[TMP1]]) ]
+; CHECK-NEXT: unreachable
+; CHECK: [[IF_END]]:
+; CHECK-NEXT: catchret from [[TMP1]] to label %[[SETJMP_DISPATCH]]
+;
+entry:
+ %x = alloca i32, align 4
+ call void @llvm.lifetime.start.p0(i64 4, ptr %x)
+ %call = call i32 @setjmp(ptr @buf) returns_twice
+ %cmp = icmp eq i32 %call, 0
+ br i1 %cmp, label %if, label %else
+
+if:
+ call void @dummy()
+ ret void
+
+else:
+ call void @llvm.lifetime.end.p0(i64 4, ptr %x)
+ ret void
+}
+
+define void @test_dynamic(i32 %size) {
+; CHECK-LABEL: define void @test_dynamic(
+; CHECK-SAME: i32 [[SIZE:%.*]]) personality ptr @__gxx_wasm_personality_v0 {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: [[FUNCTIONINVOCATIONID:%.*]] = alloca i32, align 4
+; CHECK-NEXT: br label %[[SETJMP_DISPATCH:.*]]
+; CHECK: [[SETJMP_DISPATCH]]:
+; CHECK-NEXT: [[VAL1:%.*]] = phi i32 [ [[VAL:%.*]], %[[IF_END:.*]] ], [ undef, %[[ENTRY]] ]
+; CHECK-NEXT: [[LABEL_PHI:%.*]] = phi i32 [ [[LABEL:%.*]], %[[IF_END]] ], [ -1, %[[ENTRY]] ]
+; CHECK-NEXT: switch i32 [[LABEL_PHI]], label %[[ENTRY_SPLIT:.*]] [
+; CHECK-NEXT: i32 1, label %[[ENTRY_SPLIT_SPLIT:.*]]
+; CHECK-NEXT: ]
+; CHECK: [[ENTRY_SPLIT]]:
+; CHECK-NEXT: [[X:%.*]] = alloca i32, i32 [[SIZE]], align 4
+; CHECK-NEXT: call void @__wasm_setjmp(ptr @buf, i32 1, ptr [[FUNCTIONINVOCATIONID]])
+; CHECK-NEXT: br label %[[ENTRY_SPLIT_SPLIT]]
+; CHECK: [[ENTRY_SPLIT_SPLIT]]:
+; CHECK-NEXT: [[SETJMP_RET:%.*]] = phi i32 [ 0, %[[ENTRY_SPLIT]] ], [ [[VAL1]], %[[SETJMP_DISPATCH]] ]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[SETJMP_RET]], 0
+; CHECK-NEXT: br i1 [[CMP]], label %[[IF:.*]], label %[[ELSE:.*]]
+; CHECK: [[IF]]:
+; CHECK-NEXT: invoke void @dummy()
+; CHECK-NEXT: to [[DOTNOEXC:label %.*]] unwind label %[[CATCH_DISPATCH_LONGJMP:.*]]
+; CHECK: [[_NOEXC:.*:]]
+; CHECK-NEXT: ret void
+; CHECK: [[ELSE]]:
+; CHECK-NEXT: ret void
+; CHECK: [[CATCH_DISPATCH_LONGJMP]]:
+; CHECK-NEXT: [[TMP0:%.*]] = catchswitch within none [label %catch.longjmp] unwind to caller
+; CHECK: [[CATCH_LONGJMP:.*:]]
+; CHECK-NEXT: [[TMP1:%.*]] = catchpad within [[TMP0]] []
+; CHECK-NEXT: [[THROWN:%.*]] = call ptr @llvm.wasm.catch(i32 1)
+; CHECK-NEXT: [[ENV_GEP:%.*]] = getelementptr { ptr, i32 }, ptr [[THROWN]], i32 0, i32 0
+; CHECK-NEXT: [[VAL_GEP:%.*]] = getelementptr { ptr, i32 }, ptr [[THROWN]], i32 0, i32 1
+; CHECK-NEXT: [[ENV:%.*]] = load ptr, ptr [[ENV_GEP]], align 4
+; CHECK-NEXT: [[VAL]] = load i32, ptr [[VAL_GEP]], align 4
+; CHECK-NEXT: [[LABEL]] = call i32 @__wasm_setjmp_test(ptr [[ENV]], ptr [[FUNCTIONINVOCATIONID]]) [ "funclet"(token [[TMP1]]) ]
+; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[LABEL]], 0
+; CHECK-NEXT: br i1 [[TMP2]], label %[[IF_THEN:.*]], label %[[IF_END]]
+; CHECK: [[IF_THEN]]:
+; CHECK-NEXT: call void @__wasm_longjmp(ptr [[ENV]], i32 [[VAL]]) [ "funclet"(token [[TMP1]]) ]
+; CHECK-NEXT: unreachable
+; CHECK: [[IF_END]]:
+; CHECK-NEXT: catchret from [[TMP1]] to label %[[SETJMP_DISPATCH]]
+;
+entry:
+ %x = alloca i32, i32 %size, align 4
+ call void @llvm.lifetime.start.p0(i64 -1, ptr %x)
+ %call = call i32 @setjmp(ptr @buf) returns_twice
+ %cmp = icmp eq i32 %call, 0
+ br i1 %cmp, label %if, label %else
+
+if:
+ call void @dummy()
+ ret void
+
+else:
+ call void @llvm.lifetime.end.p0(i64 -1, ptr %x)
+ ret void
+}
diff --git a/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-debuginfo.ll b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-debuginfo.ll
index fec9836a1607c..bab8403aa7b9e 100644
--- a/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-debuginfo.ll
+++ b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj-debuginfo.ll
@@ -16,10 +16,10 @@ entry:
call void @foo(), !dbg !7
ret void, !dbg !8
; CHECK: entry:
- ; CHECK-NEXT: %functionInvocationId = alloca i32, align 4, !dbg ![[DL0:.*]]
+ ; CHECK-NEXT: %buf = alloca [1 x %struct.__jmp_buf_tag], align 16, !dbg ![[DL0:.*]]
+ ; CHECK-NEXT: %functionInvocationId = alloca i32, align 4, !dbg ![[DL0]]
; CHECK: entry.split:
- ; CHECK: alloca {{.*}}, !dbg ![[DL0]]
; CHECK: call void @__wasm_setjmp{{.*}}, !dbg ![[DL1:.*]]
; CHECK-NEXT: br {{.*}}, !dbg ![[DL2:.*]]
diff --git a/llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll
index b584342adc91f..51dcf2fc7ec62 100644
--- a/llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll
+++ b/llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll
@@ -22,17 +22,17 @@ entry:
call void @longjmp(ptr %buf, i32 1) #1
unreachable
; CHECK: entry:
+; CHECK-NEXT: %buf = alloca [1 x %struct.__jmp_buf_tag], align 16
; CHECK-NEXT: %functionInvocationId = alloca i32, align 4
; CHECK-NEXT: br label %entry.split
; CHECK: entry.split
-; CHECK-NEXT: %[[BUF:.*]] = alloca [1 x %struct.__jmp_buf_tag]
-; CHECK-NEXT: call void @__wasm_setjmp(ptr %[[BUF]], i32 1, ptr %functionInvocationId)
+; CHECK-NEXT: call void @__wasm_setjmp(ptr %buf, i32 1, ptr %functionInvocationId)
; CHECK-NEXT: br label %entry.split.split
; CHECK: entry.split.split:
; CHECK-NEXT: phi i32 [ 0, %entry.split ], [ %[[LONGJMP_RESULT:.*]], %if.end ]
-; CHECK-NEXT: %[[JMPBUF:.*]] = ptrtoint ptr %[[BUF]] to [[PTR]]
+; CHECK-NEXT: %[[JMPBUF:.*]] = ptrtoint ptr %buf to [[PTR]]
; CHECK-NEXT: store [[PTR]] 0, ptr @__THREW__
; CHECK-NEXT: call cc{{.*}} void @__invoke_void_[[PTR]]_i32(ptr @emscripten_longjmp, [[PTR]] %[[JMPBUF]], i32 1)
; CHECK-NEXT: %[[__THREW__VAL:.*]] = load [[PTR]], ptr @__THREW__
diff --git a/llvm/test/CodeGen/WebAssembly/lower-wasm-ehsjlj.ll b/llvm/test/CodeGen/WebAssembly/lower-wasm-ehsjlj.ll
index b4c93c49a97c2..9de6652d48cbf 100644
--- a/llvm/test/CodeGen/WebAssembly/lower-wasm-ehsjlj.ll
+++ b/llvm/test/CodeGen/WebAssembly/lower-wasm-ehsjlj.ll
@@ -108,7 +108,7 @@ catch: ; preds = %catch.start
call void @__cxa_end_catch() [ "funclet"(token %2) ]
catchret from %2 to label %catchret.dest
; CHECK: catch: ; preds = %catch.start
-; CHECK-NEXT: %exn = load ptr, ptr %exn.slot6, align 4
+; CHECK-NEXT: %exn = load ptr, ptr %exn.slot, align 4
; CHECK-NEXT: %5 = call ptr @__cxa_begin_catch(ptr %exn) #3 [ "funclet"(token %2) ]
; CHECK-NEXT: invoke void @__cxa_end_catch() [ "funclet"(token %2) ]
; CHECK-NEXT: to label %.noexc unwind label %catch.dispatch.longjmp
diff --git a/llvm/test/CodeGen/WebAssembly/lower-wasm-sjlj.ll b/llvm/test/CodeGen/WebAssembly/lower-wasm-sjlj.ll
index 82c04e24b72f1..e1cb859b5562f 100644
--- a/llvm/test/CodeGen/WebAssembly/lower-wasm-sjlj.ll
+++ b/llvm/test/CodeGen/WebAssembly/lower-wasm-sjlj.ll
@@ -25,26 +25,24 @@ entry:
unreachable
; CHECK: entry:
+; CHECK-NEXT: %buf = alloca [1 x %struct.__jmp_buf_tag], align 16
; CHECK-NEXT: %functionInvocationId = alloca i32, align 4
; CHECK-NEXT: br label %setjmp.dispatch
; CHECK: setjmp.dispatch:
; CHECK-NEXT: %[[VAL2:.*]] = phi i32 [ %val, %if.end ], [ undef, %entry ]
-; CHECK-NEXT: %[[BUF:.*]] = phi ptr [ %[[BUF2:.*]], %if.end ], [ undef, %entry ]
; CHECK-NEXT: %label.phi = phi i32 [ %label, %if.end ], [ -1, %entry ]
; CHECK-NEXT: switch i32 %label.phi, label %entry.split [
; CHECK-NEXT: i32 1, label %entry.split.split
; CHECK-NEXT: ]
; CHECK: entry.split:
-; CHECK-NEXT: %buf = alloca [1 x %struct.__jmp_buf_tag], align 16
; CHECK-NEXT: call void @__wasm_setjmp(ptr %buf, i32 1, ptr %functionInvocationId)
; CHECK-NEXT: br label %entry.split.split
; CHECK: entry.split.split:
-; CHECK-NEXT: %[[BUF2]] = phi ptr [ %[[BUF]], %setjmp.dispatch ], [ %buf, %entry.split ]
; CHECK-NEXT: %setjmp.ret = phi i32 [ 0, %entry.split ], [ %[[VAL2]], %setjmp.dispatch ]
-; CHECK-NEXT: invoke void @__wasm_longjmp(ptr %[[BUF2]], i32 1)
+; CHECK-NEXT: invoke void @__wasm_longjmp(ptr %buf, i32 1)
; CHECK-NEXT: to label %.noexc unwind label %catch.dispatch.longjmp
; CHECK: .noexc:
|
You can test this locally with the following command:git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 'HEAD~1' HEAD llvm/test/CodeGen/WebAssembly/lower-em-sjlj-alloca.ll llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp llvm/test/CodeGen/WebAssembly/lower-em-sjlj-debuginfo.ll llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll llvm/test/CodeGen/WebAssembly/lower-wasm-ehsjlj.ll llvm/test/CodeGen/WebAssembly/lower-wasm-sjlj.llThe following files introduce new uses of undef:
Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields In tests, avoid using For example, this is considered a bad practice: define void @fn() {
...
br i1 undef, ...
}Please use the following instead: define void @fn(i1 %cond) {
...
br i1 %cond, ...
}Please refer to the Undefined Behavior Manual for more information. |
aheejin
approved these changes
Jul 28, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
After #149310 lifetime intrinsics require an alloca argument, an invariant that this pass can break.
I've fixed this in two ways:
Fixes #150498.