From acdac5391dd6a511f844b9b3556b42e62b2ff7c4 Mon Sep 17 00:00:00 2001
From: lzkk <956449176@qq.com>
Date: Mon, 25 May 2026 21:00:32 +0800
Subject: [PATCH] =?UTF-8?q?fix(backend):=20EmitLargeImmediate=20=E8=B7=B3?=
 =?UTF-8?q?=E8=BF=87=E5=89=8D=E5=AF=BC=E9=9B=B6=EF=BC=8C=E9=81=BF=E5=85=8D?=
 =?UTF-8?q?=E5=86=97=E4=BD=99=20movz=20#0?=
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32-bit 立即数低 16 位为零时（如 0x00020000），直接发射移位
movz 而非 movz #0 + movk 双指令。crypto -7, fft -2, h-4 -1,
h-10 -1，总计 -33 条，零退化。
---
 src/mir/AsmPrinter.cpp |  5 +++++
 优化记录.md        | 12 ++++++++++++
 指令数基线.md     | 24 ++++++++++++------------
 3 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/src/mir/AsmPrinter.cpp b/src/mir/AsmPrinter.cpp
index 827b053f..756deeb1 100644
--- a/src/mir/AsmPrinter.cpp
+++ b/src/mir/AsmPrinter.cpp
@@ -223,6 +223,11 @@ namespace mir
                 {
                     continue;
                 }
+                // 跳过前导零——直接用移位后的 movz，避免浪费 movz #0
+                if (!emitted && part == 0)
+                {
+                    continue;
+                }
 
                 if (!emitted)
                 {
diff --git a/优化记录.md b/优化记录.md
index 8580c0e1..1013368e 100644
--- a/优化记录.md
+++ b/优化记录.md
@@ -45,3 +45,15 @@
 - **效果**：functional 测试从 87/88 → **100/100 全部通过**
 - **已知局限**：30_many_dimensions（19 维多维数组参数）仍失败，该 bug 在降级层（无优化也错），需专项修复 GEP 偏移计算
 - **后续**：30_many_dimensions 已知根因在多维数组 GEP 降级，待后续处理
+
+---
+
+## 2026-05-25 | Movz #0 前导零优化
+
+- **类型**：后端（AsmPrinter）
+- **假设**：EmitLargeImmediate 中，当 32-bit 立即数的低 16-bit 为零时，应该直接用移位后的 movz，而不是先 `movz #0` 再 `movk`。例如 `0x00020000` → `movz w8, #2, lsl #16` 而非 `movz w8, #0; movk w8, #2, lsl #16`
+- **实现**：AsmPrinter.cpp EmitLargeImmediate 循环中，`!emitted && part == 0` 时跳过（3 行），保持底部 `!emitted → mov #0` 兜底处理全零情况
+- **指令数效果**：减少 33 条，crypto -7×3、fft -2×3、h-4 -1×3、h-10 -1×3
+- **退化**：无
+- **功能测试**：100/100 functional 通过，30/31 h_functional 通过（1 个预存故障 30_many_dimensions）
+- **已知局限**：仅修复 EmitLargeImmediate；EmitStackAdjust/EmitAddressFromBase 中的 movz 模式仍有同样问题，可后续统一
diff --git a/指令数基线.md b/指令数基线.md
index e2640a91..7238b973 100644
--- a/指令数基线.md
+++ b/指令数基线.md
@@ -32,21 +32,21 @@
 | performance/crc1 | 279 |
 | performance/crc2 | 279 |
 | performance/crc3 | 279 |
-| performance/crypto-1 | 1926 |
-| performance/crypto-2 | 1926 |
-| performance/crypto-3 | 1926 |
-| performance/fft0 | 597 |
-| performance/fft1 | 597 |
-| performance/fft2 | 597 |
+| performance/crypto-1 | 1919 |
+| performance/crypto-2 | 1919 |
+| performance/crypto-3 | 1919 |
+| performance/fft0 | 595 |
+| performance/fft1 | 595 |
+| performance/fft2 | 595 |
 | performance/h-1-01 | 157 |
 | performance/h-1-02 | 157 |
 | performance/h-1-03 | 157 |
-| performance/h-10-01 | 328 |
-| performance/h-10-02 | 328 |
-| performance/h-10-03 | 328 |
-| performance/h-4-01 | 163 |
-| performance/h-4-02 | 163 |
-| performance/h-4-03 | 163 |
+| performance/h-10-01 | 327 |
+| performance/h-10-02 | 327 |
+| performance/h-10-03 | 327 |
+| performance/h-4-01 | 162 |
+| performance/h-4-02 | 162 |
+| performance/h-4-03 | 162 |
 | performance/h-5-01 | 338 |
 | performance/h-5-02 | 338 |
 | performance/h-5-03 | 338 |