[CIR][CIRGen] Support __builtin_isinf_sign

This patch adds support for `__builtin_isinf_sign`. The implementation
has several limitations that result in discrepancies between the
generated LLVM IR and the expected output.

Firstly, it uses `IsFPClass` to determine if a value is infinite,
whereas the original CGBuiltin implementation used direct comparisons
with infinity constants.
Secondly, due to #480, there are
numerous unnecessary type conversions occurring, such as converting from
i1 to i8 and then back to i1.
Additionally, `SignBitOp` cannot set the return type to `CIR_BoolType`,
as doing so would lead to failures during the lowering to LLVM IR.

Author: PikachuHyA

clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h

@@ -489,6 +489,10 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
     return createCast(cir::CastKind::int_to_ptr, src, newTy);
   }
 
+  mlir::Value createIntToBoolCast(mlir::Value v) {
+    return createCast(cir::CastKind::int_to_bool, v, getBoolTy());
+  }
+
   mlir::Value createGetMemberOp(mlir::Location &loc, mlir::Value structPtr,
                                 const char *fldName, unsigned idx) {
 

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

@@ -1385,6 +1385,27 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
   case Builtin::BI__builtin_matrix_column_major_store:
     llvm_unreachable("BI__builtin_matrix_column_major_store NYI");
 
+  case Builtin::BI__builtin_isinf_sign: {
+    CIRGenFunction::CIRGenFPOptionsRAII FPOptsRAII(*this, E);
+    mlir::Location Loc = getLoc(E->getBeginLoc());
+    mlir::Value V = emitScalarExpr(E->getArg(0));
+    mlir::Value IsInf = builder.createIsFPClass(Loc, V, FPClassTest::fcInf);
+    // FIMXE: CIR now will convert cir::BoolType to i8 type unconditionally.
+    // see https://github.com/llvm/clangir/issues/480
+    // fix the issue can eliminate lots of redundant cast instruction
+    // for IsInf, i1 -> i8 -> i1
+    // for IsNeg, i1 -> i8 -> i32 -> i1
+    mlir::Value IsNeg = emitSignBit(Loc, *this, V);
+    IsNeg = builder.createIntToBoolCast(IsNeg);
+    auto IntTy = ConvertType(E->getType());
+    auto Zero = builder.getNullValue(IntTy, Loc);
+    auto One = builder.getConstant(Loc, cir::IntAttr::get(IntTy, 1));
+    auto NegativeOne = builder.getConstant(Loc, cir::IntAttr::get(IntTy, -1));
+    auto SignResult = builder.createSelect(Loc, IsNeg, NegativeOne, One);
+    auto Result = builder.createSelect(Loc, IsInf, SignResult, Zero);
+    return RValue::get(Result);
+  }
+
   case Builtin::BI__builtin_flt_rounds:
     llvm_unreachable("BI__builtin_flt_rounds NYI");
 

clang/test/CIR/CodeGen/builtin-isinf-sign.c

@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+
+int test_float_isinf_sign(float x) {
+    // CIR-LABEL: test_float_isinf_sign
+    // CIR: %[[TMP0:.*]] = cir.load %{{.*}} : !cir.ptr<!cir.float>, !cir.float
+    // CIR: %[[IS_INF:.*]] = cir.is_fp_class %[[TMP0]], 516 : (!cir.float) -> !cir.bool
+    // CIR: %[[TMP1:.*]] = cir.signbit %[[TMP0]] : !cir.float -> !s32i
+    // CIR: %[[IS_NEG:.*]] = cir.cast(int_to_bool, %[[TMP1]] : !s32i), !cir.bool
+    // CIR: %[[C_0:.*]] = cir.const #cir.int<0> : !s32i
+    // CIR: %[[C_1:.*]] = cir.const #cir.int<1> : !s32i
+    // CIR: %[[C_m1:.*]] = cir.const #cir.int<-1> : !s32i
+    // CIR: %[[TMP4:.*]] = cir.select if %[[IS_NEG]] then %[[C_m1]] else %[[C_1]] : (!cir.bool, !s32i, !s32i) -> !s32i
+    // CIR: %10 = cir.select if %[[IS_INF]] then %[[TMP4]] else %[[C_0]] : (!cir.bool, !s32i, !s32i) -> !s32i
+
+    // LLVM-LABEL: test_float_isinf_sign
+    // LLVM: %[[TMP0:.*]] = load float, ptr %{{.*}}
+    // LLVM: %[[IS_INF:.*]] = call i1 @llvm.is.fpclass.f32(float %[[TMP0]], i32 516)
+    // LLVM: %[[IS_INF_I8:.*]] = zext i1 %[[IS_INF]] to i8
+    // LLVM: %[[TMP1:.*]] = bitcast float %[[TMP0]] to i32
+    // LLVM: %[[IS_NEG:.*]] = icmp slt i32 %[[TMP1]], 0
+    // FIXME: eliminate the redundant instruction
+    // [[IS_NEG]] changes bool -> i8 -> i32 -> i1
+    // LLVM: %[[TMP2:.*]] = select i1 %{{.*}}, i32 -1, i32 1
+    // LLVM: %[[IS_INF_I1:.*]] = trunc i8 %[[IS_INF_I8]] to i1
+    // LLVM: %{{.*}} = select i1 %[[IS_INF_I1]], i32 %[[TMP2]], i32 0
+    return __builtin_isinf_sign(x);
+}