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[backend]修复浮点数截断逻辑 h36通过

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This commit is contained in:
CGH0S7
2025-08-05 02:43:46 +08:00
parent b1efd481b4
commit f2477c4af3
3 changed files with 23 additions and 73 deletions
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1
src/backend/RISCv64/RISCv64AsmPrinter.cpp
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@ -106,6 +106,7 @@ void RISCv64AsmPrinter::printInstruction(MachineInstr* instr, bool debug) {
case RVOpcodes::FMV_S: *OS << "fmv.s "; break;
case RVOpcodes::FMV_W_X: *OS << "fmv.w.x "; break;
case RVOpcodes::FMV_X_W: *OS << "fmv.x.w "; break;
case RVOpcodes::FSRMI: *OS << "fsrmi "; break;
case RVOpcodes::CALL: { // 为CALL指令添加特殊处理逻辑
*OS << "call ";
// 遍历所有操作数，只寻找并打印函数名标签

92
src/backend/RISCv64/RISCv64ISel.cpp
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@ -745,83 +745,29 @@ void RISCv64ISel::selectNode(DAGNode* node) {
CurMBB->addInstruction(std::move(instr));
break;
}
case Instruction::kFtoI: { // 浮点 to 整数 (带向下取整)
// 目标：实现 floor(x) 的效果, C/C++中浮点转整数是截断(truncate)
// 对于正数，floor(x) == truncate(x)
// RISC-V的 fcvt.w.s 默认是“四舍五入到偶数”
// 我们需要手动实现截断逻辑
// 逻辑:
// temp_i = fcvt.w.s(x) // 四舍五入
// temp_f = fcvt.s.w(temp_i) // 转回浮点
// if (x < temp_f) { // 如果原数更小，说明被“五入”了
// result = temp_i - 1
// } else {
// result = temp_i
// }
auto temp_i_vreg = getNewVReg(Type::getIntType());
auto temp_f_vreg = getNewVReg(Type::getFloatType());
auto cmp_vreg = getNewVReg(Type::getIntType());
case Instruction::kFtoI: { // 浮点 to 整数 (C/C++: 截断)
// C/C++ 标准要求向零截断 (truncate), 对应的RISC-V舍入模式是 RTZ (Round Towards Zero).
// fcvt.w.s 指令使用 fcsr 中的 frm 字段来决定舍入模式。
// 我们需要手动设置 frm=1 (RTZ), 执行转换, 然后恢复 frm=0 (RNE, 默认).
// 1. fcvt.w.s temp_i_vreg, src_vreg
auto fcvt_w = std::make_unique<MachineInstr>(RVOpcodes::FCVT_W_S);
fcvt_w->addOperand(std::make_unique<RegOperand>(temp_i_vreg));
fcvt_w->addOperand(std::make_unique<RegOperand>(src_vreg));
CurMBB->addInstruction(std::move(fcvt_w));
// 1. fsrmi x0, 1 (set rounding mode to RTZ)
auto fsrmi1 = std::make_unique<MachineInstr>(RVOpcodes::FSRMI);
fsrmi1->addOperand(std::make_unique<RegOperand>(PhysicalReg::ZERO));
fsrmi1->addOperand(std::make_unique<ImmOperand>(1));
CurMBB->addInstruction(std::move(fsrmi1));
// 2. fcvt.s.w temp_f_vreg, temp_i_vreg
auto fcvt_s = std::make_unique<MachineInstr>(RVOpcodes::FCVT_S_W);
fcvt_s->addOperand(std::make_unique<RegOperand>(temp_f_vreg));
fcvt_s->addOperand(std::make_unique<RegOperand>(temp_i_vreg));
CurMBB->addInstruction(std::move(fcvt_s));
// 2. fcvt.w.s dest_vreg, src_vreg
auto fcvt = std::make_unique<MachineInstr>(RVOpcodes::FCVT_W_S);
fcvt->addOperand(std::make_unique<RegOperand>(dest_vreg));
fcvt->addOperand(std::make_unique<RegOperand>(src_vreg));
CurMBB->addInstruction(std::move(fcvt));
// 3. flt.s cmp_vreg, src_vreg, temp_f_vreg
auto flt = std::make_unique<MachineInstr>(RVOpcodes::FLT_S);
flt->addOperand(std::make_unique<RegOperand>(cmp_vreg));
flt->addOperand(std::make_unique<RegOperand>(src_vreg));
flt->addOperand(std::make_unique<RegOperand>(temp_f_vreg));
CurMBB->addInstruction(std::move(flt));
// 3. fsrmi x0, 0 (restore rounding mode to RNE)
auto fsrmi0 = std::make_unique<MachineInstr>(RVOpcodes::FSRMI);
fsrmi0->addOperand(std::make_unique<RegOperand>(PhysicalReg::ZERO));
fsrmi0->addOperand(std::make_unique<ImmOperand>(0));
CurMBB->addInstruction(std::move(fsrmi0));
// 创建标签
int unique_id = this->local_label_counter++;
std::string rounded_up_label = MFunc->getName() + "_ftoi_rounded_up_" + std::to_string(unique_id);
std::string done_label = MFunc->getName() + "_ftoi_done_" + std::to_string(unique_id);
// 4. bne cmp_vreg, x0, rounded_up_label
auto bne = std::make_unique<MachineInstr>(RVOpcodes::BNE);
bne->addOperand(std::make_unique<RegOperand>(cmp_vreg));
bne->addOperand(std::make_unique<RegOperand>(PhysicalReg::ZERO));
bne->addOperand(std::make_unique<LabelOperand>(rounded_up_label));
CurMBB->addInstruction(std::move(bne));
// 5. else 分支: mv dest_vreg, temp_i_vreg
auto mv = std::make_unique<MachineInstr>(RVOpcodes::MV);
mv->addOperand(std::make_unique<RegOperand>(dest_vreg));
mv->addOperand(std::make_unique<RegOperand>(temp_i_vreg));
CurMBB->addInstruction(std::move(mv));
// 6. j done_label
auto j = std::make_unique<MachineInstr>(RVOpcodes::J);
j->addOperand(std::make_unique<LabelOperand>(done_label));
CurMBB->addInstruction(std::move(j));
// 7. rounded_up_label:
auto label_up = std::make_unique<MachineInstr>(RVOpcodes::LABEL);
label_up->addOperand(std::make_unique<LabelOperand>(rounded_up_label));
CurMBB->addInstruction(std::move(label_up));
// 8. addiw dest_vreg, temp_i_vreg, -1
auto addi = std::make_unique<MachineInstr>(RVOpcodes::ADDIW);
addi->addOperand(std::make_unique<RegOperand>(dest_vreg));
addi->addOperand(std::make_unique<RegOperand>(temp_i_vreg));
addi->addOperand(std::make_unique<ImmOperand>(-1));
CurMBB->addInstruction(std::move(addi));
// 9. done_label:
auto label_done = std::make_unique<MachineInstr>(RVOpcodes::LABEL);
label_done->addOperand(std::make_unique<LabelOperand>(done_label));
CurMBB->addInstruction(std::move(label_done));
break;
}
case Instruction::kFNeg: { // 浮点取负

3
src/include/backend/RISCv64/RISCv64LLIR.h
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@ -96,6 +96,9 @@ enum class RVOpcodes {
FMV_X_W, // fmv.x.w rd, rs1 (浮点寄存器位模式 -> 整数寄存器)
FNEG_S, // fneg.s rd, rs (浮点取负)
// 浮点控制状态寄存器 (CSR)
FSRMI, // fsrmi rd, imm (设置舍入模式立即数)
// 伪指令
FRAME_LOAD_W, // 从栈帧加载 32位 Word (对应 lw)
FRAME_LOAD_D, // 从栈帧加载 64位 Doubleword (对应 ld)