[clang] Implement constexpr support for __builtin_popcountg

[overmighty]

No description provided.

[overmighty]

cc @RKSimon

[llvmbot]

@llvm/pr-subscribers-clang

Author: OverMighty (overmighty)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/84318.diff

4 Files Affected:

• (modified) clang/docs/LanguageExtensions.rst (+1)
• (modified) clang/include/clang/Basic/Builtins.td (+1-1)
• (modified) clang/lib/AST/ExprConstant.cpp (+1)
• (modified) clang/test/Sema/constant-builtins-2.c (+7)

diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 2b54dffd058a35..06af93fd3c15ca 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -5378,6 +5378,7 @@ The following builtin intrinsics can be used in constant expressions:
 * ``__builtin_popcount``
 * ``__builtin_popcountl``
 * ``__builtin_popcountll``
+* ``__builtin_popcountg``
 * ``__builtin_rotateleft8``
 * ``__builtin_rotateleft16``
 * ``__builtin_rotateleft32``
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index a81131d82c4cb4..9c703377ca8d3e 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -706,7 +706,7 @@ def Popcount : Builtin, BitInt_Long_LongLongTemplate {
 
 def Popcountg : Builtin {
   let Spellings = ["__builtin_popcountg"];
-  let Attributes = [NoThrow, Const, CustomTypeChecking];
+  let Attributes = [NoThrow, Const, Constexpr, CustomTypeChecking];
   let Prototype = "int(...)";
 }
 
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index d8ca35740fbc35..4a7c7755e1d6fd 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -12483,6 +12483,7 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__builtin_popcount:
   case Builtin::BI__builtin_popcountl:
   case Builtin::BI__builtin_popcountll:
+  case Builtin::BI__builtin_popcountg:
   case Builtin::BI__popcnt16: // Microsoft variants of popcount
   case Builtin::BI__popcnt:
   case Builtin::BI__popcnt64: {
diff --git a/clang/test/Sema/constant-builtins-2.c b/clang/test/Sema/constant-builtins-2.c
index 2bdd7b06daabfe..9ac0ddf94be4fe 100644
--- a/clang/test/Sema/constant-builtins-2.c
+++ b/clang/test/Sema/constant-builtins-2.c
@@ -237,6 +237,13 @@ char popcount7[__builtin_popcountl(~0L) == BITSIZE(long) ? 1 : -1];
 char popcount8[__builtin_popcountll(0LL) == 0 ? 1 : -1];
 char popcount9[__builtin_popcountll(0xF0F0LL) == 8 ? 1 : -1];
 char popcount10[__builtin_popcountll(~0LL) == BITSIZE(long long) ? 1 : -1];
+char popcount11[__builtin_popcountg(0U) == 0 ? 1 : -1];
+char popcount12[__builtin_popcountg(0xF0F0U) == 8 ? 1 : -1];
+char popcount13[__builtin_popcountg(~0U) == BITSIZE(int) ? 1 : -1];
+char popcount14[__builtin_popcountg(~0UL) == BITSIZE(long) ? 1 : -1];
+char popcount15[__builtin_popcountg(~0ULL) == BITSIZE(long long) ? 1 : -1];
+char popcount15[__builtin_popcountg(~(unsigned __int128)0) == BITSIZE(__int128) ? 1 : -1];
+char popcount16[__builtin_popcountg(~(unsigned _BitInt(128))0) == BITSIZE(_BitInt(128)) ? 1 : -1];
 
 char parity1[__builtin_parity(0) == 0 ? 1 : -1];
 char parity2[__builtin_parity(0xb821) == 0 ? 1 : -1];

[Sirraide]

This needs a release note, but LGTM otherwise.

[Sirraide]

I’ll wait for CI to finish building the docs and then merge this; it was passing before, so I don’t think we need to wait for it again as the only thing that has changed since then is the release notes.

[Sirraide]

I see the name of one of the arrays was wrong; we really should just refactor this entire test to just use static_assert; not in this pr, though.

[overmighty]

Yes, I had actually caught the mistake but somehow reintroduced it at some point.

[overmighty]

Usage of __int128 in the test broke the clang-armv8-quick build: https://lab.llvm.org/buildbot/#/builders/245/builds/21611/steps/5/logs/FAIL__Clang__constant-builtins-2_c.