[llvm] [LoongArch] Return true from shouldConsiderGEPOffsetSplit (PR #88371)

[via llvm-commits]

https://github.com/wangleiat updated https://github.com/llvm/llvm-project/pull/88371

>From 511d4afd54bd7cd249d0d243c68f005baf21782e Mon Sep 17 00:00:00 2001
From: wanglei <wanglei at loongson.cn>
Date: Thu, 11 Apr 2024 17:01:08 +0800
Subject: [PATCH] [LoongArch] Return true from shouldConsiderGEPOffsetSplit

If not performing gep splits can prevent important optimizations, such
as preventing the element indices / member offsets from being
(partially) folded into load/store instruction immediates.
---
 llvm/lib/Target/LoongArch/LoongArchISelLowering.h         | 1 +
 llvm/test/Transforms/CodeGenPrepare/LoongArch/splitgep.ll | 6 +++---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/LoongArch/LoongArchISelLowering.h b/llvm/lib/Target/LoongArch/LoongArchISelLowering.h
index 9e9ac0b8269291..4bb6c049f8d758 100644
--- a/llvm/lib/Target/LoongArch/LoongArchISelLowering.h
+++ b/llvm/lib/Target/LoongArch/LoongArchISelLowering.h
@@ -238,6 +238,7 @@ class LoongArchTargetLowering : public TargetLowering {
   bool isShuffleMaskLegal(ArrayRef<int> Mask, EVT VT) const override {
     return false;
   }
+  bool shouldConsiderGEPOffsetSplit() const override { return true; }
 
 private:
   /// Target-specific function used to lower LoongArch calling conventions.
diff --git a/llvm/test/Transforms/CodeGenPrepare/LoongArch/splitgep.ll b/llvm/test/Transforms/CodeGenPrepare/LoongArch/splitgep.ll
index ca2a16a0ca7ecd..20cc25e95adf97 100644
--- a/llvm/test/Transforms/CodeGenPrepare/LoongArch/splitgep.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/LoongArch/splitgep.ll
@@ -4,9 +4,9 @@
 define void @test(ptr %sp, ptr %t, i32 %n) {
 ; CHECK-LABEL: @test(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    %s = load ptr, ptr %sp, align 8
-; CHECK-NEXT:    br label %while_cond
-
+; CHECK-NEXT:    %splitgep1 = getelementptr i8, ptr %t, i64 80000
+; CHECK-NEXT:    %s = load ptr, ptr %sp
+; CHECK-NEXT:    %splitgep = getelementptr i8, ptr %s, i64 80000
 entry:
   %s = load ptr, ptr %sp
   br label %while_cond