[clang] fa70ee4 - [CIR] Implement __builtin_flt_rounds and __builtin_set_flt_rounds (#190706)

[via cfe-commits]

Author: Andy Kaylor
Date: 2026-04-06T17:11:49-07:00
New Revision: fa70ee45be461d5d997fc7aac4e39f48be9d21ee

URL: https://github.com/llvm/llvm-project/commit/fa70ee45be461d5d997fc7aac4e39f48be9d21ee
DIFF: https://github.com/llvm/llvm-project/commit/fa70ee45be461d5d997fc7aac4e39f48be9d21ee.diff

LOG: [CIR] Implement __builtin_flt_rounds and __builtin_set_flt_rounds (#190706)

This adds CIR handling for the __builtin_flt_rounds and
__builtin_set_flt_rounds builtin functions. Because the LLVM dialect
does not have dedicated operations for these, I have chosen not to
implement them as operations in CIR either. Instead, we just call the
LLVM intrinsic.

Added: 
    

Modified: 
    clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
    clang/test/CIR/CodeGenBuiltins/builtins-floating-point.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
index c03858ba8da50..523348a952775 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
@@ -1580,9 +1580,23 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
     mlir::Value result = builder.createSelect(loc, isInf, signResult, zero);
     return RValue::get(result);
   }
-  case Builtin::BI__builtin_flt_rounds:
-  case Builtin::BI__builtin_set_flt_rounds:
-    return errorBuiltinNYI(*this, e, builtinID);
+  case Builtin::BI__builtin_flt_rounds: {
+    mlir::Location loc = getLoc(e->getExprLoc());
+    mlir::Type resultType = convertType(e->getType());
+    mlir::Value result =
+        builder.emitIntrinsicCallOp(loc, "get.rounding", resultType);
+    if (result.getType() != resultType)
+      result =
+          builder.createCast(loc, cir::CastKind::integral, result, resultType);
+    return RValue::get(result);
+  }
+  case Builtin::BI__builtin_set_flt_rounds: {
+    mlir::Location loc = getLoc(e->getExprLoc());
+    mlir::Value v = emitScalarExpr(e->getArg(0));
+    builder.emitIntrinsicCallOp(loc, "set.rounding", builder.getVoidTy(),
+                                mlir::ValueRange{v});
+    return RValue::get(nullptr);
+  }
   case Builtin::BI__builtin_fpclassify: {
     CIRGenFunction::CIRGenFPOptionsRAII fPOptsRAII(*this, e);
     mlir::Location loc = getLoc(e->getBeginLoc());

diff  --git a/clang/test/CIR/CodeGenBuiltins/builtins-floating-point.c b/clang/test/CIR/CodeGenBuiltins/builtins-floating-point.c
index be82137427ea2..c3306ccbada01 100644
--- a/clang/test/CIR/CodeGenBuiltins/builtins-floating-point.c
+++ b/clang/test/CIR/CodeGenBuiltins/builtins-floating-point.c
@@ -2210,3 +2210,29 @@ double my_roundeven(double x) {
   // OGCG: define{{.*}}@my_roundeven(
   // OGCG: call double @llvm.roundeven.f64(
 }
+
+int my_flt_rounds(void) {
+  return __builtin_flt_rounds();
+  // CIR: cir.func no_inline dso_local @my_flt_rounds
+  // CIR:   cir.call_llvm_intrinsic "get.rounding"  : () -> !s32i
+
+  // LLVM: define{{.*}} i32 @my_flt_rounds
+  // LLVM:   call i32 @llvm.get.rounding()
+  // LLVM: }
+
+  // OGCG: define{{.*}}@my_flt_rounds
+  // OGCG: call i32 @llvm.get.rounding()
+}
+
+void my_set_flt_rounds(int rounding) {
+  __builtin_set_flt_rounds(rounding);
+  // CIR: cir.func no_inline dso_local @my_set_flt_rounds
+  // CIR:   cir.call_llvm_intrinsic "set.rounding" %{{.*}} : (!s32i)
+
+  // LLVM: define{{.*}} void @my_set_flt_rounds
+  // LLVM:   call void @llvm.set.rounding(i32 %{{.+}})
+  // LLVM: }
+
+  // OGCG: define{{.*}}@my_set_flt_rounds
+  // OGCG: call void @llvm.set.rounding(i32 %{{.+}})
+}