[CIR][CIRGen] Support __builtin_signbitl (#1117)

follow #1033
handle `LongDoubleType` with `FP80Type`.

Author: PikachuHyA

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -4365,8 +4365,11 @@ class CIRSignBitOpLowering : public mlir::OpConversionPattern<cir::SignBitOp> {
     if (auto longDoubleType =
             mlir::dyn_cast<cir::LongDoubleType>(op.getInput().getType())) {
       if (mlir::isa<cir::FP80Type>(longDoubleType.getUnderlying())) {
-        // see https://github.com/llvm/clangir/issues/1057
-        llvm_unreachable("NYI");
+        // If the underlying type of LongDouble is FP80Type,
+        // DataLayout::getTypeSizeInBits returns 128.
+        // See https://github.com/llvm/clangir/issues/1057.
+        // Set the width to 80 manually.
+        width = 80;
       }
     }
     auto intTy = mlir::IntegerType::get(rewriter.getContext(), width);

clang/test/CIR/CodeGen/builtin-signbit.c

@@ -23,3 +23,13 @@ void test_signbit_double(double val) {
     // LLVM: %{{.+}} = zext i1 [[TMP2]] to i32
     __builtin_signbitf(val);
 }
+
+void test_signbit_long_double(long double val) {
+    // CIR: test_signbit_long_double
+    // LLVM: test_signbit_long_double
+    __builtin_signbitl(val);
+    // CIR: %{{.+}} = cir.signbit %{{.+}} : !cir.long_double<!cir.f80> -> !s32i
+    // LLVM: [[TMP1:%.*]] = bitcast x86_fp80 %{{.+}} to i80
+    // LLVM: [[TMP2:%.*]] = icmp slt i80 [[TMP1]], 0
+    // LLVM: %{{.+}} = zext i1 [[TMP2]] to i32
+}