[CIR] CountOf VLA with Array element type #169404
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-clangir Author: Amr Hesham (AmrDeveloper) ChangesImplement CountOf on VariableArrayType with IntegerConstant SizeExpr Full diff: https://github.com/llvm/llvm-project/pull/169404.diff 2 Files Affected:
diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index 7c94743d5ffc6..feb019292715c 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -2325,14 +2325,27 @@ 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) {
+ 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(
diff --git a/clang/test/CIR/CodeGen/count-of.c b/clang/test/CIR/CodeGen/count-of.c
new file mode 100644
index 0000000000000..78c905e285969
--- /dev/null
+++ b/clang/test/CIR/CodeGen/count-of.c
@@ -0,0 +1,28 @@
+// 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() {
+ long size;
+#define int_arr int[5]
+ return _Countof(int_arr[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
|
andykaylor
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This looks fine, except for an issue with the test case. The implementation for evaluateExtent looks small. Why not include that in this same PR?
clang/test/CIR/CodeGen/count-of.c
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| #define int_arr int[5] | ||
| return _Countof(int_arr[size]); |
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This is an off way to represent the array. Why are you using #define here? Also, I believe this is using an uninitialized variable to describe a two-dimensional array, which is likely UB. Maybe make the variable an argument?
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In this test case, I want to create an array type, not an array int[5][size] 🤔, i think it's TypeExpr and will not init array right?
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The rest of the evaluateExtent implementation has one part related to CountOf and other parts are related to sizeof, I will address the countof part here and all sizeof part will be in follow up PR if thats okey
🐧 Linux x64 Test Results
All tests passed but another part of the build failed. Click on a failure below to see the details. tools/clang/lib/CIR/CodeGen/CMakeFiles/obj.clangCIR.dir/CIRGenFunction.cpp.oIf these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the |
andykaylor
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Nov 25, 2025
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| 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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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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I'm preparing a fix for it now.
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Thank you for catching it
tanji-dg
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Nov 27, 2025
Implement CountOf on VariableArrayType with IntegerConstant SizeExpr
GeneraluseAI
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Implement CountOf on VariableArrayType with IntegerConstant SizeExpr
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Implement CountOf on VariableArrayType with IntegerConstant SizeExpr