https://github.com/ckoparkar updated
https://github.com/llvm/llvm-project/pull/158048
>From 7665f0d152250b327b93a8aedc2ed9410e22277c Mon Sep 17 00:00:00 2001
From: Chaitanya Koparkar <ckopar...@gmail.com>
Date: Thu, 11 Sep 2025 07:24:02 -0400
Subject: [PATCH 1/4] [Clang] Allow __builtin_fma/fmaf/fmal to be used in a
constant expression
---
clang/include/clang/Basic/Builtins.td | 2 +-
clang/lib/AST/ByteCode/InterpBuiltin.cpp | 8 ++++++++
clang/lib/AST/ExprConstant.cpp | 12 ++++++++----
3 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/clang/include/clang/Basic/Builtins.td
b/clang/include/clang/Basic/Builtins.td
index 27639f06529cb..a22a6e68db83b 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -199,7 +199,7 @@ def FloorF16F128 : Builtin, F16F128MathTemplate {
def FmaF16F128 : Builtin, F16F128MathTemplate {
let Spellings = ["__builtin_fma"];
- let Attributes = [FunctionWithBuiltinPrefix, NoThrow,
ConstIgnoringErrnoAndExceptions];
+ let Attributes = [FunctionWithBuiltinPrefix, NoThrow,
ConstIgnoringErrnoAndExceptions, Constexpr];
let Prototype = "T(T, T, T)";
}
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index a0dcdace854b9..55baa4891bb32 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -3411,6 +3411,14 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC,
const CallExpr *Call,
case clang::X86::BI__builtin_ia32_pmuludq512:
return interp__builtin_ia32_pmul(S, OpPC, Call, BuiltinID);
+ case Builtin::BIfma:
+ case Builtin::BIfmal:
+ case Builtin::BIfmaf:
+ case Builtin::BI__builtin_fma:
+ case Builtin::BI__builtin_fmal:
+ case Builtin::BI__builtin_fmaf:
+ case Builtin::BI__builtin_fmaf16:
+ case Builtin::BI__builtin_fmaf128:
case Builtin::BI__builtin_elementwise_fma:
return interp__builtin_elementwise_triop_fp(
S, OpPC, Call,
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index ca930737474df..dbff682714342 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -16346,11 +16346,15 @@ bool FloatExprEvaluator::VisitCallExpr(const CallExpr
*E) {
return true;
}
+ case Builtin::BIfma:
+ case Builtin::BIfmal:
+ case Builtin::BIfmaf:
+ case Builtin::BI__builtin_fma:
+ case Builtin::BI__builtin_fmal:
+ case Builtin::BI__builtin_fmaf:
+ case Builtin::BI__builtin_fmaf16:
+ case Builtin::BI__builtin_fmaf128:
case Builtin::BI__builtin_elementwise_fma: {
- if (!E->getArg(0)->isPRValue() || !E->getArg(1)->isPRValue() ||
- !E->getArg(2)->isPRValue()) {
- return false;
- }
APFloat SourceY(0.), SourceZ(0.);
if (!EvaluateFloat(E->getArg(0), Result, Info) ||
!EvaluateFloat(E->getArg(1), SourceY, Info) ||
>From c61e699ff10d9c43cf78de46b31ff5b76e3134a3 Mon Sep 17 00:00:00 2001
From: Chaitanya Koparkar <ckopar...@gmail.com>
Date: Sat, 13 Sep 2025 09:06:20 -0400
Subject: [PATCH 2/4] Make all fma variants constexpr, add tests
---
clang/include/clang/Basic/Builtins.td | 2 +-
clang/test/AST/ByteCode/builtin-functions.cpp | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/Basic/Builtins.td
b/clang/include/clang/Basic/Builtins.td
index a22a6e68db83b..956e76085a08f 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -3885,7 +3885,7 @@ def Floor : FPMathTemplate, LibBuiltin<"math.h"> {
def Fma : FPMathTemplate, LibBuiltin<"math.h"> {
let Spellings = ["fma"];
- let Attributes = [NoThrow, ConstIgnoringErrnoAndExceptions];
+ let Attributes = [NoThrow, ConstIgnoringErrnoAndExceptions, Constexpr];
let Prototype = "T(T, T, T)";
let AddBuiltinPrefixedAlias = 1;
}
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp
b/clang/test/AST/ByteCode/builtin-functions.cpp
index f47bc49d9a1a8..961495bb2ad0a 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -1742,6 +1742,19 @@ namespace Invalid {
// both-note {{in call to}}
}
+namespace Fma {
+ static_assert(__builtin_fma(2.0, 3.0, 4.0) == 10.0);
+ static_assert(__builtin_fma(200.0, 300.0, 400.0) == 60400.0);
+ static_assert(__builtin_fmal(2.0, 3.0, 4.0) == 10.0);
+ static_assert(__builtin_fmal(200.0, 300.0, 400.0) == 60400.0);
+ static_assert(__builtin_fmaf(2.0, 3.0, 4.0) == 10.0);
+ static_assert(__builtin_fmaf(200.0, 300.0, 400.0) == 60400.0);
+ static_assert(__builtin_fmaf16(2.0, 3.0, 4.0) == 10.0);
+ static_assert(__builtin_fmaf16(200.0, 300.0, 400.0) == 60416.0);
+ static_assert(__builtin_fmaf128(2.0, 3.0, 4.0) == 10.0);
+ static_assert(__builtin_fmaf128(200.0, 300.0, 400.0) == 60400.0);
+}
+
#if __cplusplus >= 202002L
namespace WithinLifetime {
constexpr int a = 10;
>From 0016026eb7e712eb3c41e290a272448e2996c15f Mon Sep 17 00:00:00 2001
From: Chaitanya Koparkar <ckopar...@gmail.com>
Date: Sat, 13 Sep 2025 18:45:24 -0400
Subject: [PATCH 3/4] constexpr-cxx23-clang.pass.cpp tests
---
.../libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
index 3f17f21e8c108..dfa991201fb67 100644
--- a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
+++ b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
@@ -194,11 +194,19 @@ int main(int, char**) {
ASSERT_NOT_CONSTEXPR_CXX23(std::fminf(1.0f, 0.0f) == 0.0f);
ASSERT_NOT_CONSTEXPR_CXX23(std::fminl(1.0L, 0.0L) == 0.0L);
+#if !__has_constexpr_builtin(__builtin_fma)
ASSERT_NOT_CONSTEXPR_CXX23(std::fma(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_NOT_CONSTEXPR_CXX23(std::fma(1.0, 1.0, 1.0) == 2.0);
ASSERT_NOT_CONSTEXPR_CXX23(std::fma(1.0L, 1.0L, 1.0L) == 2.0L);
ASSERT_NOT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_NOT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
+#else
+ ASSERT_CONSTEXPR_CXX23(std::fma(1.0f, 1.0f, 1.0f) == 2.0f);
+ ASSERT_CONSTEXPR_CXX23(std::fma(1.0, 1.0, 1.0) == 2.0);
+ ASSERT_CONSTEXPR_CXX23(std::fma(1.0L, 1.0L, 1.0L) == 2.0L);
+ ASSERT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
+ ASSERT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
+#endif
ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0f) == FP_NORMAL);
ASSERT_NOT_CONSTEXPR_CXX23(std::fpclassify(-1.0) == FP_NORMAL);
>From 33999a84488855eaf4547caf69e565e4cb63565a Mon Sep 17 00:00:00 2001
From: Chaitanya Koparkar <ckopar...@gmail.com>
Date: Wed, 17 Sep 2025 06:19:00 -0400
Subject: [PATCH 4/4] Fix tests, not all fmas are constexpr yet
---
.../test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp | 2 --
1 file changed, 2 deletions(-)
diff --git a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
index dfa991201fb67..e03a86f1f6f52 100644
--- a/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
+++ b/libcxx/test/libcxx/numerics/c.math/constexpr-cxx23-clang.pass.cpp
@@ -201,9 +201,7 @@ int main(int, char**) {
ASSERT_NOT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_NOT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
#else
- ASSERT_CONSTEXPR_CXX23(std::fma(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_CONSTEXPR_CXX23(std::fma(1.0, 1.0, 1.0) == 2.0);
- ASSERT_CONSTEXPR_CXX23(std::fma(1.0L, 1.0L, 1.0L) == 2.0L);
ASSERT_CONSTEXPR_CXX23(std::fmaf(1.0f, 1.0f, 1.0f) == 2.0f);
ASSERT_CONSTEXPR_CXX23(std::fmal(1.0L, 1.0L, 1.0L) == 2.0L);
#endif
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