From a3222e1dd7aa84a87053e08d6c1c35ab1700ed54 Mon Sep 17 00:00:00 2001
From: Fred Chow <fredchow@gitee.com>
Date: Thu, 20 May 2021 23:53:14 -0700
Subject: [PATCH] Do not apply backward substitution for agg types <= 16 bytes,
 because it interferes with cg's struct return optimizaton

---
 src/mapleall/maple_me/src/hdse.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/mapleall/maple_me/src/hdse.cpp b/src/mapleall/maple_me/src/hdse.cpp
index 11422e2f38..b21b584bfd 100644
--- a/src/mapleall/maple_me/src/hdse.cpp
+++ b/src/mapleall/maple_me/src/hdse.cpp
@@ -43,7 +43,12 @@ void HDSE::CheckBackSubsCandidacy(DassignMeStmt *dass) {
     return;
   }
   ScalarMeExpr *lhsscalar = static_cast<ScalarMeExpr *>(dass->GetLHS());
-  if (!lhsscalar->GetOst()->IsLocal()) {
+  OriginalSt *ost = lhsscalar->GetOst();
+  if (!ost->IsLocal()) {
+    return;
+  }
+  MIRType *ty = GlobalTables::GetTypeTable().GetTypeFromTyIdx(ost->GetTyIdx());
+  if (ty->GetPrimType() == PTY_agg && ty->GetSize() <= 16) {
     return;
   }
   ScalarMeExpr *rhsscalar = static_cast<ScalarMeExpr *>(dass->GetRHS());
-- 
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