[llvm] [LoongArch] Enable `AllNBitUsers` checking for {DIV, MOD}.W{U} with div32 enabled (PR #118776)

[via llvm-commits]

https://github.com/heiher created https://github.com/llvm/llvm-project/pull/118776

None

>From c488ac1d2e93a40243a07c5f1730ac8af32a469b Mon Sep 17 00:00:00 2001
From: WANG Rui <wangrui at loongson.cn>
Date: Thu, 5 Dec 2024 17:45:07 +0800
Subject: [PATCH] [LoongArch] Enable `AllNBitUsers` checking for {DIV,MOD}.W{U}
 with div32 enabled

---
 llvm/lib/Target/LoongArch/LoongArchOptWInstrs.cpp  | 14 +++++++++-----
 .../ir-instruction/sdiv-udiv-srem-urem-div32.ll    |  7 +++----
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Target/LoongArch/LoongArchOptWInstrs.cpp b/llvm/lib/Target/LoongArch/LoongArchOptWInstrs.cpp
index ab90409fdf47d0..51e5e288a25124 100644
--- a/llvm/lib/Target/LoongArch/LoongArchOptWInstrs.cpp
+++ b/llvm/lib/Target/LoongArch/LoongArchOptWInstrs.cpp
@@ -139,11 +139,6 @@ static bool hasAllNBitUsers(const MachineInstr &OrigMI,
       case LoongArch::MULH_WU:
       case LoongArch::MULW_D_W:
       case LoongArch::MULW_D_WU:
-      // TODO: {DIV,MOD}.{W,WU} consumes the upper 32 bits before LA664+.
-      // case LoongArch::DIV_W:
-      // case LoongArch::DIV_WU:
-      // case LoongArch::MOD_W:
-      // case LoongArch::MOD_WU:
       case LoongArch::SLL_W:
       case LoongArch::SLLI_W:
       case LoongArch::SRL_W:
@@ -170,6 +165,15 @@ static bool hasAllNBitUsers(const MachineInstr &OrigMI,
         if (Bits >= 32)
           break;
         return false;
+      // {DIV,MOD}.W{U} consumes the upper 32 bits if the div32
+      // feature is not enabled.
+      case LoongArch::DIV_W:
+      case LoongArch::DIV_WU:
+      case LoongArch::MOD_W:
+      case LoongArch::MOD_WU:
+        if (Bits >= 32 && ST.hasDiv32())
+          break;
+        return false;
       case LoongArch::MOVGR2CF:
         if (Bits >= 1)
           break;
diff --git a/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem-div32.ll b/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem-div32.ll
index 7e7518154e8397..9276195b6fa0b4 100644
--- a/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem-div32.ll
+++ b/llvm/test/CodeGen/LoongArch/ir-instruction/sdiv-udiv-srem-urem-div32.ll
@@ -84,10 +84,9 @@ define signext i32 @sextw_rmv(i32 signext %a, i32 signext %b, i32 signext %c) {
 ;
 ; LA64-DIV32-LABEL: sextw_rmv:
 ; LA64-DIV32:       # %bb.0: # %entry
-; LA64-DIV32-NEXT:    mul.d $a0, $a1, $a0
-; LA64-DIV32-NEXT:    addi.w $a1, $a0, 0
-; LA64-DIV32-NEXT:    div.w $a0, $a2, $a0
-; LA64-DIV32-NEXT:    sltu $a0, $a0, $a1
+; LA64-DIV32-NEXT:    mul.w $a0, $a1, $a0
+; LA64-DIV32-NEXT:    div.w $a1, $a2, $a0
+; LA64-DIV32-NEXT:    sltu $a0, $a1, $a0
 ; LA64-DIV32-NEXT:    ret
 entry:
   %mul = mul nsw i32 %b, %a