[CIR] Add undef handling to enable global lambdas #169721
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This change adds undef handling that was needed to enable global lambdas. There was no lambda-specific code needed, but the global lambda handling needed to initialize a global with an undef value. [CIR] Handle undef init of struct This adds handling for a case where Clang initializes a struct to undef with a constant copy. This required adding support for undef constants and lowering undef attributes to LLVM IR.
andykaylor
requested review from
bcardosolopes,
erichkeane,
lanza and
xlauko
llvmbot
added
clang
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@llvm/pr-subscribers-clangir @llvm/pr-subscribers-clang Author: Andy Kaylor (andykaylor) ChangesThis change adds undef handling that was needed to enable global lambdas. There was no lambda-specific code needed, but the global lambda handling needed to initialize a global with an undef value. [CIR] Handle undef init of struct This adds handling for a case where Clang initializes a struct to undef with a constant copy. This required adding support for undef constants and lowering undef attributes to LLVM IR. Full diff: https://github.com/llvm/llvm-project/pull/169721.diff 3 Files Affected:
diff --git a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
index 6bf543cf794b7..92fd591e3a37d 100644
--- a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
+++ b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
@@ -330,6 +330,12 @@ static LogicalResult checkConstantTypes(mlir::Operation *op, mlir::Type opType,
"zero expects struct, array, vector, or complex type");
}
+ if (isa<cir::UndefAttr>(attrType)) {
+ if (!::mlir::isa<cir::VoidType>(opType))
+ return success();
+ return op->emitOpError("undef expects non-void type");
+ }
+
if (mlir::isa<cir::BoolAttr>(attrType)) {
if (!mlir::isa<cir::BoolType>(opType))
return op->emitOpError("result type (")
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index cd923a15af132..9e62317bff5f6 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -240,7 +240,7 @@ class CIRAttrToValue {
.Case<cir::IntAttr, cir::FPAttr, cir::ConstComplexAttr,
cir::ConstArrayAttr, cir::ConstRecordAttr, cir::ConstVectorAttr,
cir::ConstPtrAttr, cir::GlobalViewAttr, cir::TypeInfoAttr,
- cir::VTableAttr, cir::ZeroAttr>(
+ cir::UndefAttr, cir::VTableAttr, cir::ZeroAttr>(
[&](auto attrT) { return visitCirAttr(attrT); })
.Default([&](auto attrT) { return mlir::Value(); });
}
@@ -254,6 +254,7 @@ class CIRAttrToValue {
mlir::Value visitCirAttr(cir::ConstVectorAttr attr);
mlir::Value visitCirAttr(cir::GlobalViewAttr attr);
mlir::Value visitCirAttr(cir::TypeInfoAttr attr);
+ mlir::Value visitCirAttr(cir::UndefAttr attr);
mlir::Value visitCirAttr(cir::VTableAttr attr);
mlir::Value visitCirAttr(cir::ZeroAttr attr);
@@ -591,6 +592,13 @@ mlir::Value CIRAttrToValue::visitCirAttr(cir::TypeInfoAttr typeInfoAttr) {
return result;
}
+/// UndefAttr visitor.
+mlir::Value CIRAttrToValue::visitCirAttr(cir::UndefAttr undefAttr) {
+ mlir::Location loc = parentOp->getLoc();
+ return mlir::LLVM::UndefOp::create(
+ rewriter, loc, converter->convertType(undefAttr.getType()));
+}
+
// VTableAttr visitor.
mlir::Value CIRAttrToValue::visitCirAttr(cir::VTableAttr vtableArr) {
mlir::Type llvmTy = converter->convertType(vtableArr.getType());
@@ -2048,7 +2056,8 @@ CIRToLLVMGlobalOpLowering::matchAndRewriteRegionInitializedGlobal(
// TODO: Generalize this handling when more types are needed here.
assert((isa<cir::ConstArrayAttr, cir::ConstRecordAttr, cir::ConstVectorAttr,
cir::ConstPtrAttr, cir::ConstComplexAttr, cir::GlobalViewAttr,
- cir::TypeInfoAttr, cir::VTableAttr, cir::ZeroAttr>(init)));
+ cir::TypeInfoAttr, cir::VTableAttr, cir::UndefAttr,
+ cir::ZeroAttr>(init)));
// TODO(cir): once LLVM's dialect has proper equivalent attributes this
// should be updated. For now, we use a custom op to initialize globals
@@ -2106,7 +2115,8 @@ mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
} else if (mlir::isa<cir::ConstArrayAttr, cir::ConstVectorAttr,
cir::ConstRecordAttr, cir::ConstPtrAttr,
cir::ConstComplexAttr, cir::GlobalViewAttr,
- cir::TypeInfoAttr, cir::VTableAttr, cir::ZeroAttr>(
+ cir::TypeInfoAttr, cir::UndefAttr, cir::VTableAttr,
+ cir::ZeroAttr>(
init.value())) {
// TODO(cir): once LLVM's dialect has proper equivalent attributes this
// should be updated. For now, we use a custom op to initialize globals
diff --git a/clang/test/CIR/CodeGen/lambda.cpp b/clang/test/CIR/CodeGen/lambda.cpp
index 91380b9bea296..84d446727d6e3 100644
--- a/clang/test/CIR/CodeGen/lambda.cpp
+++ b/clang/test/CIR/CodeGen/lambda.cpp
@@ -8,6 +8,39 @@
// We declare anonymous record types to represent lambdas. Rather than trying to
// to match the declarations, we establish variables for these when they are used.
+auto global_lambda = [](){};
+void use_global_lambda() {
+ global_lambda();
+}
+
+// CIR: cir.global "private" internal dso_local @global_lambda = #cir.undef : ![[REC_LAM_GLOBAL_LAMBDA:.*]] {alignment = 1 : i64}
+// CIR: cir.func lambda internal private dso_local @_ZNK3$_0clEv(%[[THIS_ARG:.*]]: !cir.ptr<![[REC_LAM_GLOBAL_LAMBDA]]> {{.*}})
+// CIR: %[[THIS:.*]] = cir.alloca !cir.ptr<![[REC_LAM_GLOBAL_LAMBDA]]>, !cir.ptr<!cir.ptr<![[REC_LAM_GLOBAL_LAMBDA]]>>, ["this", init]
+// CIR: cir.store %[[THIS_ARG]], %[[THIS]]
+// CIR: cir.load %[[THIS]]
+//
+// CIR: cir.func {{.*}} @_Z17use_global_lambdav()
+// CIR: %[[LAMBDA:.*]] = cir.get_global @global_lambda : !cir.ptr<![[REC_LAM_GLOBAL_LAMBDA]]>
+// CIR: cir.call @_ZNK3$_0clEv(%[[LAMBDA]]) : (!cir.ptr<![[REC_LAM_GLOBAL_LAMBDA]]>) -> ()
+
+// LLVM: @global_lambda = internal global %class.anon.0 undef, align 1
+// LLVM: define internal void @"_ZNK3$_0clEv"(ptr %[[THIS_ARG:.*]])
+// LLVM: %[[THIS_ADDR:.*]] = alloca ptr
+// LLVM: store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// LLVM: %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]
+//
+// LLVM: define dso_local void @_Z17use_global_lambdav()
+// LLVM: call void @"_ZNK3$_0clEv"(ptr @global_lambda)
+
+// OGCG: @global_lambda = internal global %class.anon undef, align 1
+// OGCG: define dso_local void @_Z17use_global_lambdav()
+// OGCG: call void @"_ZNK3$_0clEv"(ptr noundef nonnull align 1 dereferenceable(1) @global_lambda)
+//
+// OGCG: define internal void @"_ZNK3$_0clEv"(ptr {{.*}} %[[THIS_ARG:.*]])
+// OGCG: %[[THIS_ADDR:.*]] = alloca ptr
+// OGCG: store ptr %[[THIS_ARG]], ptr %[[THIS_ADDR]]
+// OGCG: %[[THIS:.*]] = load ptr, ptr %[[THIS_ADDR]]
+
void fn() {
auto a = [](){};
a();
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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| mlir::Value visit(mlir::Attribute attr) { | ||
| return llvm::TypeSwitch<mlir::Attribute, mlir::Value>(attr) | ||
| .Case<cir::IntAttr, cir::FPAttr, cir::ConstComplexAttr, |
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Its a Little weird to me that this is a hand-typed list here, and that we don't have some sort of tablegen to get this list? Perhaps a task for a future patch :)
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We could possibly do that in a way similar to what @Lancern did here: #159390
I'm not sure it's worth the effort though. I don't expect there to ever be a huge number of cases that need to be handled here. This doesn't cover every CIR-specific attribute, only attributes that have a reason (and a way) to be converted to a value in the LLVM dialect. If we had a tablegen for this, we'd still need to provide a CIRAttrToValue::visitCirAttr implementation for anything that wasn't trivially convertible (as IntAttr and FPAttr are).
There are two more in the incubator that we haven't upstreamed yet, bool and poison. I was going to say that I didn't know why we aren't seeing problems related to bool being missing, but I just discovered that it's because we didn't have a test for it (bool initializers for globals are being lowered incorrectly!). I'll fix that shortly.
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Ah, I guess if we're 'near the end' here, that is probably fine. This just looked like the kind of list that would get bad really fast as we grew.
One thing we've done in the past is have the declaration of things like visitCirAttr tablegen'ed, and leave it to the linker to let you know when you've forgotten that. But the lack of compile-time errors on forgetting something like this in a list is unfortunate.
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On closer inspection, the problem with boolean global initializers is something in the LLVM dialect to LLVM IR translation for the constant. We don't appear to be hitting this visitor for BoolAttr in any case I've found. Maybe it isn't needed.
| mlir::Value visitCirAttr(cir::ConstVectorAttr attr); | ||
| mlir::Value visitCirAttr(cir::GlobalViewAttr attr); | ||
| mlir::Value visitCirAttr(cir::TypeInfoAttr attr); | ||
| mlir::Value visitCirAttr(cir::UndefAttr attr); |
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This list could/should probably be tablegen'ed/macro'ed too (in a future patch).
| } | ||
|
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||
| if (isa<cir::UndefAttr>(attrType)) { | ||
| if (!::mlir::isa<cir::VoidType>(opType)) |
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| if (!::mlir::isa<cir::VoidType>(opType)) | |
| if (!isa<cir::VoidType>(opType)) |
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or add mlir:: in both cases here?
| assert( | ||
| (isa<cir::ConstArrayAttr, cir::ConstRecordAttr, cir::ConstVectorAttr, | ||
| cir::ConstPtrAttr, cir::ConstComplexAttr, cir::GlobalViewAttr, | ||
| cir::TypeInfoAttr, cir::VTableAttr, cir::UndefAttr, cir::ZeroAttr>( |
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| cir::TypeInfoAttr, cir::VTableAttr, cir::UndefAttr, cir::ZeroAttr>( | |
| cir::TypeInfoAttr, cir::UndefAttr, cir::VTableAttr, cir::ZeroAttr>( |
This change adds undef handling that was needed to enable global lambdas. There was no lambda-specific code needed, but the global lambda handling needed to initialize a global with an undef value. [CIR] Handle undef init of struct This adds handling for a case where Clang initializes a struct to undef with a constant copy. This required adding support for undef constants and lowering undef attributes to LLVM IR.
This change adds undef handling that was needed to enable global lambdas. There was no lambda-specific code needed, but the global lambda handling needed to initialize a global with an undef value. [CIR] Handle undef init of struct This adds handling for a case where Clang initializes a struct to undef with a constant copy. This required adding support for undef constants and lowering undef attributes to LLVM IR.
4 participants
This change adds undef handling that was needed to enable global lambdas. There was no lambda-specific code needed, but the global lambda handling needed to initialize a global with an undef value.
[CIR] Handle undef init of struct
This adds handling for a case where Clang initializes a struct to undef with a constant copy. This required adding support for undef constants and lowering undef attributes to LLVM IR.