[mips] Mark aggregates returned in registers with the 'inreg' attribute.

Summary:
This allows us to easily find them in the backend after the aggregates have
been lowered to other types. This is important on big-endian targets using
the N32/N64 ABI's since these ABI's must shift small structures into the
upper bits of the register.

Reviewers: atanasyan

Reviewed By: atanasyan

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5005

llvm-svn: 217160

1 files changed, 9 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index d33d6a09e01..4dbbc55915a 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -5561,12 +5561,15 @@ ABIArgInfo MipsABIInfo::classifyReturnType(QualType RetTy) const {
       if (RetTy->isAnyComplexType())
         return ABIArgInfo::getDirect();
 
-      // O32 returns integer vectors in registers.
-      if (IsO32 && RetTy->isVectorType() && !RetTy->hasFloatingRepresentation())
-        return ABIArgInfo::getDirect(returnAggregateInRegs(RetTy, Size));
-
-      if (!IsO32)
-        return ABIArgInfo::getDirect(returnAggregateInRegs(RetTy, Size));
+      // O32 returns integer vectors in registers and N32/N64 returns all small
+      // aggregates in registers..
+      if (!IsO32 ||
+          (RetTy->isVectorType() && !RetTy->hasFloatingRepresentation())) {
+        ABIArgInfo ArgInfo =
+            ABIArgInfo::getDirect(returnAggregateInRegs(RetTy, Size));
+        ArgInfo.setInReg(true);
+        return ArgInfo;
+      }
     }
 
     return ABIArgInfo::getIndirect(0);