[mips] For N32/N64, structs must be passed in the upper bits of a register.

[dsanders]

Summary

Most structs were fixed by r218451 but those of between >32-bits and <64-bits
remained broken since they were not marked with [ASZ]ExtUpper.
This patch fixes the remaining cases using CCPromoteToUpperBitsInType<i64> on
i64's in addition to i32 and smaller.

[vmedic]

LGTM

lib/Target/Mips/MipsCallingConv.td

def RetCC_MipsN : CallingConv<[
   CCIfType<[i64],
       CCIf<"static_cast<MipsCCState *>(&State)->WasOriginalArgF128(ValNo)",
            CCDelegateTo<RetCC_F128>>>,
 
   // Aggregate returns are positioned at the lowest address in the slot for
   // both little and big-endian targets. When passing in registers, this
   // requires that big-endian targets shift the value into the upper bits.
   CCIfSubtarget<"isLittle()",
-      CCIfType<[i8, i16, i32], CCIfInReg<CCPromoteToType<i64>>>>,
+      CCIfType<[i8, i16, i32, i64], CCIfInReg<CCPromoteToType<i64>>>>,
   CCIfSubtargetNot<"isLittle()",
-      CCIfType<[i8, i16, i32], CCIfInReg<CCPromoteToUpperBitsInType<i64>>>>,
+      CCIfType<[i8, i16, i32, i64], CCIfInReg<CCPromoteToUpperBitsInType<i64>>>>,
 
   // i32 are returned in registers V0, V1
   CCIfType<[i32], CCAssignToReg<[V0, V1]>>,
 
   // i64 are returned in registers V0_64, V1_64
   CCIfType<[i64], CCAssignToReg<[V0_64, V1_64]>>,
 
   // f32 are returned in registers F0, F2

test/CodeGen/Mips/cconv/return-struct.ll

 ; RUN: llc -mtriple=mips-linux-gnu -relocation-model=static < %s | FileCheck --check-prefix=ALL --check-prefix=O32 --check-prefix=O32-BE %s
 ; RUN: llc -mtriple=mipsel-linux-gnu -relocation-model=static < %s | FileCheck --check-prefix=ALL --check-prefix=O32 --check-prefix=O32-LE %s
 
 ; RUN-TODO: llc -mtriple=mips64-linux-gnu -relocation-model=static -mattr=-n64,+o32 < %s | FileCheck --check-prefix=ALL --check-prefix=O32 %s
 ; RUN-TODO: llc -mtriple=mips64el-linux-gnu -relocation-model=static -mattr=-n64,+o32 < %s | FileCheck --check-prefix=ALL --check-prefix=O32 %s
 
 ; RUN: llc -mtriple=mips64-linux-gnu -relocation-model=static -mattr=-n64,+n32 < %s | FileCheck --check-prefix=ALL --check-prefix=N32 --check-prefix=N32-BE %s
 ; RUN: llc -mtriple=mips64el-linux-gnu -relocation-model=static -mattr=-n64,+n32 < %s | FileCheck --check-prefix=ALL --check-prefix=N32 --check-prefix=N32-LE %s
 
 ; RUN: llc -mtriple=mips64-linux-gnu -relocation-model=static -mattr=-n64,+n64 < %s | FileCheck --check-prefix=ALL --check-prefix=N64 --check-prefix=N64-BE %s
 ; RUN: llc -mtriple=mips64el-linux-gnu -relocation-model=static -mattr=-n64,+n64 < %s | FileCheck --check-prefix=ALL --check-prefix=N64 --check-prefix=N64-LE %s
 
 ; Test struct returns for all ABI's and byte orders.
 
 @struct_byte = global {i8} zeroinitializer
 @struct_2byte = global {i8,i8} zeroinitializer
+@struct_3xi16 = global {[3 x i16]} zeroinitializer
 
 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1)
 
 define inreg {i8} @ret_struct_i8() nounwind {
 entry:
         %0 = load volatile {i8}* @struct_byte
         ret {i8} %0
 }

 ; N64-LE-DAG:        sh  [[R2]], 8([[SP:\$sp]])
 ; N64-LE-DAG:        lh  $2, 8([[SP:\$sp]])
 
 ; N64-BE-DAG:        ld  [[R1:\$[0-9]+]], %got_disp(struct_2byte)($1)
 ; N64-BE-DAG:        lhu [[R2:\$[0-9]+]], 0([[R1]])
 ; N64-BE-DAG:        sh  [[R2]], 8([[SP:\$sp]])
 ; N64-BE-DAG:        lh  [[R3:\$[0-9]+]], 8([[SP:\$sp]])
 ; N64-BE-DAG:        dsll $2, [[R3]], 48
+
+; Ensure that structures bigger than 32-bits but smaller than 64-bits are
+; also returned in the upper bits on big endian targets. Previously, these were
+; missed by the CCPromoteToType and the shift didn't happen.
+define inreg {i48} @ret_struct_3xi16() nounwind {
+entry:
+        %0 = load volatile i48* bitcast ({[3 x i16]}* @struct_3xi16 to i48*), align 2
+        %1 = insertvalue {i48} undef, i48 %0, 0
+        ret {i48} %1
+}
+
+; ALL-LABEL: ret_struct_3xi16:
+
+; O32-BE-DAG:        lui [[PTR_HI:\$[0-9]+]], %hi(struct_3xi16)
+; O32-BE-DAG:        addiu [[PTR_LO:\$[0-9]+]], [[PTR_HI]], %lo(struct_3xi16)
+; O32-BE-DAG:        lhu [[R1:\$[0-9]+]], 4([[PTR_LO]])
+; O32-BE-DAG:        lw [[R2:\$[0-9]+]], %lo(struct_3xi16)([[PTR_HI]])
+; O32-BE-DAG:        sll [[R3:\$[0-9]+]], [[R2]], 16
+; O32-BE-DAG:        or  $3, [[R1]], [[R3]]
+; O32-BE-DAG:        srl $2, [[R2]], 16
+
+; O32-LE-DAG:        lui [[PTR_HI:\$[0-9]+]], %hi(struct_3xi16)
+; O32-LE-DAG:        addiu [[PTR_LO:\$[0-9]+]], [[PTR_HI]], %lo(struct_3xi16)
+; O32-LE-DAG:        lhu $3, 4([[PTR_LO]])
+; O32-LE-DAG:        lw $2, %lo(struct_3xi16)([[PTR_HI]])
+
+; N32-LE-DAG:        lui [[PTR_HI:\$[0-9]+]], %hi(struct_3xi16)
+; N32-LE-DAG:        addiu [[PTR_LO:\$[0-9]+]], [[PTR_HI]], %lo(struct_3xi16)
+; N32-LE-DAG:        lh [[R1:\$[0-9]+]], 4([[PTR_LO]])
+; N32-LE-DAG:        lwu [[R2:\$[0-9]+]], %lo(struct_3xi16)([[PTR_HI]])
+; N32-LE-DAG:        dsll [[R3:\$[0-9]+]], [[R1]], 32
+; N32-LE-DAG:        or $2, [[R2]], [[R3]]
+
+; N32-BE-DAG:        lui [[PTR_HI:\$[0-9]+]], %hi(struct_3xi16)
+; N32-BE-DAG:        addiu [[PTR_LO:\$[0-9]+]], [[PTR_HI]], %lo(struct_3xi16)
+; N32-BE-DAG:        lw [[R1:\$[0-9]+]], %lo(struct_3xi16)([[PTR_HI]])
+; N32-BE-DAG:        dsll [[R2:\$[0-9]+]], [[R1]], 16
+; N32-BE-DAG:        lhu [[R3:\$[0-9]+]], 4([[PTR_LO]])
+; N32-BE-DAG:        or [[R4:\$[0-9]+]], [[R3]], [[R2]]
+; N32-BE-DAG:        dsll $2, [[R4]], 16
+
+; N64-LE-DAG:        ld  [[PTR:\$[0-9]+]], %got_disp(struct_3xi16)($1)
+; N64-LE-DAG:        lh [[R1:\$[0-9]+]], 4([[PTR]])
+; N64-LE-DAG:        lwu [[R2:\$[0-9]+]], 0([[PTR]])
+; N64-LE-DAG:        dsll [[R3:\$[0-9]+]], [[R1]], 32
+; N64-LE-DAG:        or $2, [[R2]], [[R3]]
+
+; N64-BE-DAG:        ld  [[PTR:\$[0-9]+]], %got_disp(struct_3xi16)($1)
+; N64-BE-DAG:        lw [[R1:\$[0-9]+]], 0([[PTR]])
+; N64-BE-DAG:        dsll [[R2:\$[0-9]+]], [[R1]], 16
+; N64-BE-DAG:        lhu [[R3:\$[0-9]+]], 4([[PTR]])
+; N64-BE-DAG:        or [[R4:\$[0-9]+]], [[R3]], [[R2]]
+; N32-BE-DAG:        dsll $2, [[R4]], 16