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new a04087f5e4 [Fix][Codegen] Avoid extraneous parentheses in if_then_else
generated code (#20285)
a04087f5e4 is described below
commit a04087f5e49b04a2c748d4624417eef9e46c55e4
Author: HeJun <[email protected]>
AuthorDate: Fri Sep 11 02:54:54 2026 +0800
[Fix][Codegen] Avoid extraneous parentheses in if_then_else generated code
(#20285)
## Problem
Since #16242, the `if_then_else` builtin call is expanded into an
if/else statement. When printing the condition, the codegen wraps it in
another pair of parentheses even though it is already parenthesized,
producing `if ((i == 0))`.
## Impact
The doubled parentheses trigger clang's `-Wparentheses-equality` warning
under `-Wall`/`-Wparentheses`, which is noisy for downstream users who
compile TVM-generated C sources with strict warning settings.
Correctness is not affected — the issue is cosmetic.
## Solution
Reuse the same leading/trailing parenthesis check as the existing
`IfThenElseNode` handling in `CodeGenC`, so a condition that already
starts and ends with parentheses is printed as-is. The generated code
now reads `if (i == 0)`.
Since `CodeGenC` is the shared base of all C-style backends (CUDA,
Metal, ROCm, Vulkan, WebGPU, Hexagon), this fix covers them all at once.
## Testing
- Added a regression test
`test_if_then_else_avoids_extraneous_parentheses` in
`tests/python/codegen/test_target_codegen_c_host.py`, which asserts the
generated C source contains no `if ((` and validates the runtime result.
- Ran the full `test_target_codegen_c_host.py` suite on aarch64 Linux
with a local build: 10/10 passed.
- `pre-commit` (clang-format, ruff-check, ruff-format) passed on the
changed files.
Co-authored-by: hejun <[email protected]>
---
src/target/source/codegen_c.cc | 6 ++++-
tests/python/codegen/test_target_codegen_c_host.py | 28 ++++++++++++++++++++++
2 files changed, 33 insertions(+), 1 deletion(-)
diff --git a/src/target/source/codegen_c.cc b/src/target/source/codegen_c.cc
index ab137d94c7..d90bb77f91 100644
--- a/src/target/source/codegen_c.cc
+++ b/src/target/source/codegen_c.cc
@@ -743,7 +743,11 @@ void CodeGenC::VisitExpr_(const CallNode* op,
std::ostream& os) { // NOLINT(*)
PrintType(op->ty, this->stream);
this->stream << " " << result << ";\n";
this->PrintIndent();
- this->stream << "if (" << cond << ") {\n";
+ if (cond[0] == '(' && cond[cond.length() - 1] == ')') {
+ this->stream << "if " << cond << " {\n";
+ } else {
+ this->stream << "if (" << cond << ") {\n";
+ }
{
int then_scope = this->BeginScope();
std::string true_val = PrintExpr(op->args[1]);
diff --git a/tests/python/codegen/test_target_codegen_c_host.py
b/tests/python/codegen/test_target_codegen_c_host.py
index 708ebb202a..0250836efa 100644
--- a/tests/python/codegen/test_target_codegen_c_host.py
+++ b/tests/python/codegen/test_target_codegen_c_host.py
@@ -293,5 +293,33 @@ def test_vector_access_ptr_address_uses_ramp_base():
assert " + 4" in call
+def test_if_then_else_avoids_extraneous_parentheses():
+ @I.ir_module
+ class Module:
+ @T.prim_func
+ def main(A: T.Buffer((8,), "int32"), B: T.Buffer((8,), "int32")):
+ for i in range(8):
+ B[i] = T.if_then_else(i == 0, 1, A[i])
+
+ built = tvm.tirx.build(Module, target="c")
+ source = built.inspect_source()
+ assert "if ((" not in source, (
+ "Generated code contains extraneous parentheses in the if condition, "
+ "which triggers clang's -Wparentheses-equality warning"
+ )
+
+ temp = utils.tempdir()
+ path_dso = temp.relpath("if_then_else.so")
+ built.export_library(path_dso)
+ loaded = tvm.runtime.load_module(path_dso)
+
+ a = tvm.runtime.tensor(np.arange(8, dtype="int32"))
+ b = tvm.runtime.tensor(np.zeros(8, dtype="int32"))
+ loaded["main"](a, b)
+ tvm.testing.assert_allclose(
+ b.numpy(), np.where(np.arange(8) == 0, 1, np.arange(8)).astype("int32")
+ )
+
+
if __name__ == "__main__":
tvm.testing.main()
