| //===-- RegisterContext_x86.cpp ---------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "RegisterContext_x86.h" |
| |
| using namespace lldb_private; |
| |
| // Convert the 8-bit abridged FPU Tag Word (as found in FXSAVE) to the full |
| // 16-bit FPU Tag Word (as found in FSAVE, and used by gdb protocol). This |
| // requires knowing the values of the ST(i) registers and the FPU Status Word. |
| uint16_t lldb_private::AbridgedToFullTagWord(uint8_t abridged_tw, uint16_t sw, |
| llvm::ArrayRef<MMSReg> st_regs) { |
| // Tag word is using internal FPU register numbering rather than ST(i). |
| // Mapping to ST(i): i = FPU regno - TOP (Status Word, bits 11:13). |
| // Here we start with FPU reg 7 and go down. |
| int st = 7 - ((sw >> 11) & 7); |
| uint16_t tw = 0; |
| for (uint8_t mask = 0x80; mask != 0; mask >>= 1) { |
| tw <<= 2; |
| if (abridged_tw & mask) { |
| // The register is non-empty, so we need to check the value of ST(i). |
| uint16_t exp = |
| st_regs[st].comp.sign_exp & 0x7fff; // Discard the sign bit. |
| if (exp == 0) { |
| if (st_regs[st].comp.mantissa == 0) |
| tw |= 1; // Zero |
| else |
| tw |= 2; // Denormal |
| } else if (exp == 0x7fff) |
| tw |= 2; // Infinity or NaN |
| // 0 if normal number |
| } else |
| tw |= 3; // Empty register |
| |
| // Rotate ST down. |
| st = (st - 1) & 7; |
| } |
| |
| return tw; |
| } |
| |
| // Convert the 16-bit FPU Tag Word to the abridged 8-bit value, to be written |
| // into FXSAVE. |
| uint8_t lldb_private::FullToAbridgedTagWord(uint16_t tw) { |
| uint8_t abridged_tw = 0; |
| for (uint16_t mask = 0xc000; mask != 0; mask >>= 2) { |
| abridged_tw <<= 1; |
| // full TW uses 11 for empty registers, aTW uses 0 |
| if ((tw & mask) != mask) |
| abridged_tw |= 1; |
| } |
| return abridged_tw; |
| } |