[clang] Additional FP classification functions

[spavloff]

C language standard defined library functions iszero, issignaling and issubnormal, which did not have counterparts among clang builtin functions. This change adds new functions:

__builtin_iszero
__builtin_issubnormal
__builtin_issignaling

They provide builtin implementation for the missing standard functions.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: Serge Pavlov (spavloff)

Changes

C language standard defined library functions iszero, issignaling and issubnormal, which did not have counterparts among clang builtin functions. This change adds new functions:

__builtin_iszero
__builtin_issubnormal
__builtin_issignaling

They provide builtin implementation for the missing standard functions.

---

Full diff: https://github.com/llvm/llvm-project/pull/69041.diff

4 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+2)
• (modified) clang/include/clang/Basic/Builtins.def (+3)
• (modified) clang/lib/CodeGen/CGBuiltin.cpp (+24)
• (modified) clang/test/CodeGen/builtins.c (+15)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2d918967e7f0b02..2453804cd7735be 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -621,6 +621,8 @@ Floating Point Support in Clang
 - Add ``__builtin_exp10``, ``__builtin_exp10f``,
   ``__builtin_exp10f16``, ``__builtin_exp10l`` and
   ``__builtin_exp10f128`` builtins.
+- Add ``__builtin_iszero``, ``__builtin_issignaling`` and
+  ``__builtin_issubnormal``.
 
 AST Matchers
 ------------
diff --git a/clang/include/clang/Basic/Builtins.def b/clang/include/clang/Basic/Builtins.def
index 6ea8484606cfd5d..ebcb5b45e5bdc23 100644
--- a/clang/include/clang/Basic/Builtins.def
+++ b/clang/include/clang/Basic/Builtins.def
@@ -494,6 +494,9 @@ BUILTIN(__builtin_isinf,      "i.", "FnctE")
 BUILTIN(__builtin_isinf_sign, "i.", "FnctE")
 BUILTIN(__builtin_isnan,      "i.", "FnctE")
 BUILTIN(__builtin_isnormal,   "i.", "FnctE")
+BUILTIN(__builtin_issubnormal,"i.", "FnctE")
+BUILTIN(__builtin_iszero,     "i.", "FnctE")
+BUILTIN(__builtin_issignaling,"i.", "FnctE")
 BUILTIN(__builtin_isfpclass,  "i.", "nctE")
 
 // FP signbit builtins
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 8cb7943df9a7822..5d3946a84b6c34a 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -3287,6 +3287,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                            ConvertType(E->getType())));
   }
 
+  case Builtin::BI__builtin_issignaling: {
+    CodeGenFunction::CGFPOptionsRAII FPOptsRAII(*this, E);
+    Value *V = EmitScalarExpr(E->getArg(0));
+    return RValue::get(
+        Builder.CreateZExt(Builder.createIsFPClass(V, FPClassTest::fcSNan),
+                           ConvertType(E->getType())));
+  }
+
   case Builtin::BI__builtin_isinf: {
     CodeGenFunction::CGFPOptionsRAII FPOptsRAII(*this, E);
     Value *V = EmitScalarExpr(E->getArg(0));
@@ -3321,6 +3329,22 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                            ConvertType(E->getType())));
   }
 
+  case Builtin::BI__builtin_issubnormal: {
+    CodeGenFunction::CGFPOptionsRAII FPOptsRAII(*this, E);
+    Value *V = EmitScalarExpr(E->getArg(0));
+    return RValue::get(
+        Builder.CreateZExt(Builder.createIsFPClass(V, FPClassTest::fcSubnormal),
+                           ConvertType(E->getType())));
+  }
+
+  case Builtin::BI__builtin_iszero: {
+    CodeGenFunction::CGFPOptionsRAII FPOptsRAII(*this, E);
+    Value *V = EmitScalarExpr(E->getArg(0));
+    return RValue::get(
+        Builder.CreateZExt(Builder.createIsFPClass(V, FPClassTest::fcZero),
+                           ConvertType(E->getType())));
+  }
+
   case Builtin::BI__builtin_isfpclass: {
     Expr::EvalResult Result;
     if (!E->getArg(1)->EvaluateAsInt(Result, CGM.getContext()))
diff --git a/clang/test/CodeGen/builtins.c b/clang/test/CodeGen/builtins.c
index 1b1b2cd6413a344..ce1182b724dcc21 100644
--- a/clang/test/CodeGen/builtins.c
+++ b/clang/test/CodeGen/builtins.c
@@ -64,6 +64,9 @@ int main(void) {
   P(isinf_sign, (1.));
   P(isnan, (1.));
   P(isfinite, (1.));
+  P(iszero, (1.));
+  P(issubnormal, (1.));
+  P(issignaling, (1.));
   P(isfpclass, (1., 1));
 
   // Bitwise & Numeric Functions
@@ -270,6 +273,18 @@ void test_float_builtins(__fp16 *H, float F, double D, long double LD) {
   // CHECK: [[TMP:%.*]] = call i1 @llvm.is.fpclass.f32(float {{.*}}, i32 264)
   // CHECK: zext i1 [[TMP]] to i32
 
+  res = __builtin_issubnormal(F);
+  // CHECK: [[TMP:%.*]] = call i1 @llvm.is.fpclass.f32(float {{.*}}, i32 144)
+  // CHECK: zext i1 [[TMP]] to i32
+
+  res = __builtin_iszero(F);
+  // CHECK: [[TMP:%.*]] = call i1 @llvm.is.fpclass.f32(float {{.*}}, i32 96)
+  // CHECK: zext i1 [[TMP]] to i32
+
+  res = __builtin_issignaling(F);
+  // CHECK: [[TMP:%.*]] = call i1 @llvm.is.fpclass.f32(float {{.*}}, i32 1)
+  // CHECK: zext i1 [[TMP]] to i32
+
   res = __builtin_flt_rounds();
   // CHECK: call i32 @llvm.get.rounding(
 }

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[spavloff]

Ping.

[tbaederr]

The clang/Interp parts LGTM

[kpneal]

The rest LGTM.

[spavloff]

Thanks!