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[CIR] CountOf VLA with Array element type #169404

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Merged
merged 2 commits into from
Nov 26, 2025
+103 −8
Merged

[CIR] CountOf VLA with Array element type #169404

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67e56c1
[CIR] CountOf VLA with Array element type
AmrDeveloper Nov 24, 2025
8eede9c
Address code review comments
AmrDeveloper Nov 25, 2025
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47 changes: 39 additions & 8 deletions clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2325,14 +2325,45 @@ mlir::Value ScalarExprEmitter::VisitUnaryExprOrTypeTraitExpr(
const QualType typeToSize = e->getTypeOfArgument();
const mlir::Location loc = cgf.getLoc(e->getSourceRange());
if (auto kind = e->getKind();
kind == UETT_SizeOf || kind == UETT_DataSizeOf) {
if (cgf.getContext().getAsVariableArrayType(typeToSize)) {
cgf.getCIRGenModule().errorNYI(e->getSourceRange(),
"sizeof operator for VariableArrayType",
e->getStmtClassName());
return builder.getConstant(
loc, cir::IntAttr::get(cgf.cgm.uInt64Ty,
llvm::APSInt(llvm::APInt(64, 1), true)));
kind == UETT_SizeOf || kind == UETT_DataSizeOf || kind == UETT_CountOf) {
if (const VariableArrayType *vat =
cgf.getContext().getAsVariableArrayType(typeToSize)) {
// For _Countof, we only want to evaluate if the extent is actually
// variable as opposed to a multi-dimensional array whose extent is
// constant but whose element type is variable.
bool evaluateExtent = true;
if (kind == UETT_CountOf && vat->getElementType()->isArrayType()) {
evaluateExtent =
!vat->getSizeExpr()->isIntegerConstantExpr(cgf.getContext());
}

if (evaluateExtent) {
if (e->isArgumentType()) {
// sizeof(type) - make sure to emit the VLA size.
cgf.emitVariablyModifiedType(typeToSize);
} else {
// C99 6.5.3.4p2: If the argument is an expression of type
// VLA, it is evaluated.
cgf.getCIRGenModule().errorNYI(
e->getSourceRange(),
"sizeof operator for VariableArrayType & evaluateExtent "
"ignoredExpr",
e->getStmtClassName());
return {};
}

// For _Countof, we just want to return the size of a single dimension.
if (kind == UETT_CountOf)
return cgf.getVLAElements1D(vat).numElts;

cgf.getCIRGenModule().errorNYI(
e->getSourceRange(),
"sizeof operator for VariableArrayType & evaluateExtent",
e->getStmtClassName());
return builder.getConstant(
loc, cir::IntAttr::get(cgf.cgm.uInt64Ty,
-llvm::APSInt(llvm::APInt(64, 1), true)));
}
}
} else if (e->getKind() == UETT_OpenMPRequiredSimdAlign) {
cgf.getCIRGenModule().errorNYI(
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8 changes: 8 additions & 0 deletions clang/lib/CIR/CodeGen/CIRGenFunction.cpp
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Expand Up @@ -1138,6 +1138,14 @@ CIRGenFunction::getVLASize(const VariableArrayType *type) {
return {numElements, elementType};
}

CIRGenFunction::VlaSizePair
CIRGenFunction::getVLAElements1D(const VariableArrayType *vla) {
mlir::Value vlaSize = vlaSizeMap[vla->getSizeExpr()];
assert(vlaSize && "no size for VLA!");
assert(vlaSize->getType() == sizeTy);
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@erichkeane erichkeane Nov 26, 2025

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vlaSize isn't a pointer, so this fails to build:

runner/_work/llvm-project/llvm-project/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
2025-11-26T19:23:08.6857824Z /home/gha/actions-runner/_work/llvm-project/llvm-project/clang/lib/CIR/CodeGen/CIRGenFunction.cpp:1145:17: error: member reference type 'mlir::Value' is not a pointer; did you mean to use '.'?
2025-11-26T19:23:08.6859083Z  1145 |   assert(vlaSize->getType() == sizeTy);
2025-11-26T19:23:08.6859503Z       |          ~~~~~~~^~
2025-11-26T19:23:08.6859814Z       |                 .
2025-11-26T19:23:08.6860251Z /usr/include/assert.h:103:27: note: expanded from macro 'assert'
2025-11-26T19:23:08.6860727Z   103 |      (static_cast <bool> (expr)                                         \
2025-11-26T19:23:08.6861052Z       |                           ^~~~

Note this seems to have been caught by pre-commit CI as well.

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@andykaylor andykaylor Nov 26, 2025

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I'm preparing a fix for it now.

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@andykaylor andykaylor Nov 26, 2025

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#169715

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@AmrDeveloper AmrDeveloper Nov 26, 2025

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Thank you for catching it

return {vlaSize, vla->getElementType()};
}

// TODO(cir): Most of this function can be shared between CIRGen
// and traditional LLVM codegen
void CIRGenFunction::emitVariablyModifiedType(QualType type) {
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4 changes: 4 additions & 0 deletions clang/lib/CIR/CodeGen/CIRGenFunction.h
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Original file line number Diff line number Diff line change
Expand Up @@ -498,6 +498,10 @@ class CIRGenFunction : public CIRGenTypeCache {
VlaSizePair(mlir::Value num, QualType ty) : numElts(num), type(ty) {}
};

/// Return the number of elements for a single dimension
/// for the given array type.
VlaSizePair getVLAElements1D(const VariableArrayType *vla);

/// Returns an MLIR::Value+QualType pair that corresponds to the size,
/// in non-variably-sized elements, of a variable length array type,
/// plus that largest non-variably-sized element type. Assumes that
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52 changes: 52 additions & 0 deletions clang/test/CIR/CodeGen/count-of.c
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@@ -0,0 +1,52 @@
// RUN: %clang_cc1 -std=c2y -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-cir %s -o %t.cir
// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
// RUN: %clang_cc1 -std=c2y -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-llvm %s -o %t-cir.ll
// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
// RUN: %clang_cc1 -std=c2y -triple x86_64-unknown-linux-gnu -Wno-unused-value -emit-llvm %s -o %t.ll
// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG

unsigned long vla_with_array_element_type_with_const_size() {
long size;
return _Countof(int[5][size]);
}

// CIR: %[[RET_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["__retval"]
// CIR: %[[SIZE_ADDR:.*]] = cir.alloca !s64i, !cir.ptr<!s64i>, ["size"]
// CIR: %[[CONST_5:.*]] = cir.const #cir.int<5> : !u64i
// CIR: cir.store %[[CONST_5]], %[[RET_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[RET_VAL:.*]] = cir.load %[[RET_ADDR]] : !cir.ptr<!u64i>, !u64i
// CIR: cir.return %[[RET_VAL]] : !u64i

// LLVM: %[[RET_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[SIZE_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: store i64 5, ptr %[[RET_ADDR]], align 8
// LLVM: %[[RET_VAL:.*]] = load i64, ptr %[[RET_ADDR]], align 8
// LLVM: ret i64 %[[RET_VAL]]

// OGCG: %[[SIZE_ADDR:.*]] = alloca i64, align 8
// OGCG: ret i64 5

unsigned long vla_with_array_element_type_non_const_size() {
long size;
return _Countof(int[size][size]);
}

// CIR: %[[REET_ADDR:.*]] = cir.alloca !u64i, !cir.ptr<!u64i>, ["__retval"]
// CIR: %[[SIZE_ADDR:.*]] = cir.alloca !s64i, !cir.ptr<!s64i>, ["size"]
// CIR: %[[TMP_SIZE:.*]] = cir.load {{.*}} %[[SIZE_ADDR]] : !cir.ptr<!s64i>, !s64i
// CIR: %[[TMP_SIZE_U64:.*]] = cir.cast integral %[[TMP_SIZE]] : !s64i -> !u64i
// CIR: cir.store %[[TMP_SIZE_U64]], %[[RET_ADDR]] : !u64i, !cir.ptr<!u64i>
// CIR: %[[TMP_RET:.*]] = cir.load %[[RET_ADDR]] : !cir.ptr<!u64i>, !u64i
// CIR: cir.return %[[TMP_RET]] : !u64i

// LLVM: %[[RET_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[SIZE_ADDR:.*]] = alloca i64, i64 1, align 8
// LLVM: %[[TMP_SIZE:.*]] = load i64, ptr %[[SIZE_ADDR]], align 8
// LLVM: store i64 %[[TMP_SIZE]], ptr %[[RET_ADDR]], align 8
// LLVM: %[[TMP_RET:.*]] = load i64, ptr %[[RET_ADDR]], align 8
// LLVM: ret i64 %[[TMP_RET]]

// OGCG: %[[SIZE_ADDR:.*]] = alloca i64, align 8
// OGCG: %[[TMP_SIZE:.*]] = load i64, ptr %[[SIZE_ADDR]], align 8
// OGCG: %[[TMP_SIZE_2:.*]] = load i64, ptr %[[SIZE_ADDR]], align 8
// OGCG: ret i64 %[[TMP_SIZE]]
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