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

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@@ -494,6 +494,10 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
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return createCast(cir::CastKind::int_to_ptr, src, newTy);
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}
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mlir::Value createIntToBoolCast(mlir::Value v) {
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return createCast(cir::CastKind::int_to_bool, v, getBoolTy());
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}
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mlir::Value createGetMemberOp(mlir::Location &loc, mlir::Value structPtr,
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const char *fldName, unsigned idx) {
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clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

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@@ -1422,6 +1422,27 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
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case Builtin::BI__builtin_matrix_column_major_store:
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llvm_unreachable("BI__builtin_matrix_column_major_store NYI");
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case Builtin::BI__builtin_isinf_sign: {
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CIRGenFunction::CIRGenFPOptionsRAII FPOptsRAII(*this, E);
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mlir::Location Loc = getLoc(E->getBeginLoc());
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mlir::Value V = emitScalarExpr(E->getArg(0));
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mlir::Value IsInf = builder.createIsFPClass(Loc, V, FPClassTest::fcInf);
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// FIMXE: CIR now will convert cir::BoolType to i8 type unconditionally.
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// see https://github.com/llvm/clangir/issues/480
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// fix the issue can eliminate lots of redundant cast instruction
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// for IsInf, i1 -> i8 -> i1
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// for IsNeg, i1 -> i8 -> i32 -> i1
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mlir::Value IsNeg = emitSignBit(Loc, *this, V);
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IsNeg = builder.createIntToBoolCast(IsNeg);
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auto IntTy = ConvertType(E->getType());
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auto Zero = builder.getNullValue(IntTy, Loc);
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auto One = builder.getConstant(Loc, cir::IntAttr::get(IntTy, 1));
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auto NegativeOne = builder.getConstant(Loc, cir::IntAttr::get(IntTy, -1));
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auto SignResult = builder.createSelect(Loc, IsNeg, NegativeOne, One);
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auto Result = builder.createSelect(Loc, IsInf, SignResult, Zero);
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return RValue::get(Result);
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}
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case Builtin::BI__builtin_flt_rounds:
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llvm_unreachable("BI__builtin_flt_rounds NYI");
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@@ -0,0 +1,30 @@
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// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
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// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
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// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll
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// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
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int test_float_isinf_sign(float x) {
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// CIR-LABEL: test_float_isinf_sign
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// CIR: %[[TMP0:.*]] = cir.load %{{.*}} : !cir.ptr<!cir.float>, !cir.float
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// CIR: %[[IS_INF:.*]] = cir.is_fp_class %[[TMP0]], 516 : (!cir.float) -> !cir.bool
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// CIR: %[[TMP1:.*]] = cir.signbit %[[TMP0]] : !cir.float -> !s32i
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// CIR: %[[IS_NEG:.*]] = cir.cast(int_to_bool, %[[TMP1]] : !s32i), !cir.bool
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// CIR: %[[C_0:.*]] = cir.const #cir.int<0> : !s32i
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// CIR: %[[C_1:.*]] = cir.const #cir.int<1> : !s32i
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// CIR: %[[C_m1:.*]] = cir.const #cir.int<-1> : !s32i
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// CIR: %[[TMP4:.*]] = cir.select if %[[IS_NEG]] then %[[C_m1]] else %[[C_1]] : (!cir.bool, !s32i, !s32i) -> !s32i
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// CIR: %10 = cir.select if %[[IS_INF]] then %[[TMP4]] else %[[C_0]] : (!cir.bool, !s32i, !s32i) -> !s32i
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// LLVM-LABEL: test_float_isinf_sign
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// LLVM: %[[TMP0:.*]] = load float, ptr %{{.*}}
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// LLVM: %[[IS_INF:.*]] = call i1 @llvm.is.fpclass.f32(float %[[TMP0]], i32 516)
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// LLVM: %[[IS_INF_I8:.*]] = zext i1 %[[IS_INF]] to i8
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// LLVM: %[[TMP1:.*]] = bitcast float %[[TMP0]] to i32
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// LLVM: %[[IS_NEG:.*]] = icmp slt i32 %[[TMP1]], 0
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// FIXME: eliminate the redundant instruction
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// [[IS_NEG]] changes bool -> i8 -> i32 -> i1
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// LLVM: %[[TMP2:.*]] = select i1 %{{.*}}, i32 -1, i32 1
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// LLVM: %[[IS_INF_I1:.*]] = trunc i8 %[[IS_INF_I8]] to i1
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// LLVM: %{{.*}} = select i1 %[[IS_INF_I1]], i32 %[[TMP2]], i32 0
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return __builtin_isinf_sign(x);
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}

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