Mips fast-isel - handle functions which return i8 or i6 .

Summary: Allow Mips fast-isel to handle functions which return i8/i16 signed/unsigned.

Test Plan:
Make check tests are forthcoming.
Already passes test-suite at O0/O2 for Mips 32 r1/r2

Reviewers: dsanders, rkotler

Subscribers: llvm-commits, rfuhler

Differential Revision: http://reviews.llvm.org/D6765

llvm-svn: 236103

3 files changed, 40 insertions, 8 deletions

diff --git a/llvm/lib/Target/Mips/MipsCallingConv.td b/llvm/lib/Target/Mips/MipsCallingConv.td
index dcd88f25d25..c2e23ffea06 100644
--- a/llvm/lib/Target/Mips/MipsCallingConv.td
+++ b/llvm/lib/Target/Mips/MipsCallingConv.td
@@ -90,6 +90,9 @@ def CC_MipsO32 : CallingConv<[
 // Only the return rules are defined here for O32. The rules for argument
 // passing are defined in MipsISelLowering.cpp.
 def RetCC_MipsO32 : CallingConv<[
+  // Promote i1/i8/i16 return values to i32.
+  CCIfType<[i1, i8, i16], CCPromoteToType<i32>>,
+
   // i32 are returned in registers V0, V1, A0, A1
   CCIfType<[i32], CCAssignToReg<[V0, V1, A0, A1]>>,
 
diff --git a/llvm/lib/Target/Mips/MipsFastISel.cpp b/llvm/lib/Target/Mips/MipsFastISel.cpp
index ab44d33cecf..671f7e90b35 100644
--- a/llvm/lib/Target/Mips/MipsFastISel.cpp
+++ b/llvm/lib/Target/Mips/MipsFastISel.cpp
@@ -1112,6 +1112,8 @@ bool MipsFastISel::finishCall(CallLoweringInfo &CLI, MVT RetVT,
       CopyVT = MVT::i32;
 
     unsigned ResultReg = createResultReg(TLI.getRegClassFor(CopyVT));
+    if (!ResultReg)
+      return false;
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
             TII.get(TargetOpcode::COPY),
             ResultReg).addReg(RVLocs[0].getLocReg());
@@ -1142,7 +1144,7 @@ bool MipsFastISel::fastLowerCall(CallLoweringInfo &CLI) {
   MVT RetVT;
   if (CLI.RetTy->isVoidTy())
     RetVT = MVT::isVoid;
-  else if (!isTypeLegal(CLI.RetTy, RetVT))
+  else if (!isTypeSupported(CLI.RetTy, RetVT))
     return false;
 
   for (auto Flag : CLI.OutFlags)
@@ -1260,13 +1262,12 @@ bool MipsFastISel::selectRet(const Instruction *I) {
       if (RVVT != MVT::i1 && RVVT != MVT::i8 && RVVT != MVT::i16)
         return false;
 
-      if (!Outs[0].Flags.isZExt() && !Outs[0].Flags.isSExt())
-        return false;
-
-      bool IsZExt = Outs[0].Flags.isZExt();
-      SrcReg = emitIntExt(RVVT, SrcReg, DestVT, IsZExt);
-      if (SrcReg == 0)
-        return false;
+      if (Outs[0].Flags.isZExt() || Outs[0].Flags.isSExt()) {
+        bool IsZExt = Outs[0].Flags.isZExt();
+        SrcReg = emitIntExt(RVVT, SrcReg, DestVT, IsZExt);
+        if (SrcReg == 0)
+          return false;
+      }
     }
 
     // Make the copy.
diff --git a/llvm/test/CodeGen/Mips/Fast-ISel/retabi.ll b/llvm/test/CodeGen/Mips/Fast-ISel/retabi.ll
index ce0ca347ada..03119b827eb 100644
--- a/llvm/test/CodeGen/Mips/Fast-ISel/retabi.ll
+++ b/llvm/test/CodeGen/Mips/Fast-ISel/retabi.ll
@@ -22,6 +22,20 @@ entry:
 }
 
 ; Function Attrs: nounwind
+define i16 @retus() {
+entry:
+; CHECK-LABEL: retus:
+  %0 = load i16, i16* @s, align 2
+  ret i16 %0
+; CHECK:        lui     $[[REG_GPa:[0-9]+]], %hi(_gp_disp)
+; CHECK:        addiu   $[[REG_GPb:[0-9]+]], $[[REG_GPa]], %lo(_gp_disp)
+; CHECK:        addu    $[[REG_GP:[0-9]+]], $[[REG_GPb]], $25
+; CHECK:        lw      $[[REG_S_ADDR:[0-9]+]], %got(s)($[[REG_GP]])
+; CHECK:        lhu     $2, 0($[[REG_S_ADDR]])
+; CHECK:        jr      $ra
+}
+
+; Function Attrs: nounwind
 define signext i16 @rets() {
 entry:
 ; CHECK-LABEL: rets:
@@ -37,6 +51,20 @@ entry:
 }
 
 ; Function Attrs: nounwind
+define i8 @retuc() {
+entry:
+; CHECK-LABEL: retuc:
+  %0 = load i8, i8* @c, align 1
+  ret i8 %0
+; CHECK:        lui     $[[REG_GPa:[0-9]+]], %hi(_gp_disp)
+; CHECK:        addiu   $[[REG_GPb:[0-9]+]], $[[REG_GPa]], %lo(_gp_disp)
+; CHECK:        addu    $[[REG_GP:[0-9]+]], $[[REG_GPb]], $25
+; CHECK:        lw      $[[REG_C_ADDR:[0-9]+]], %got(c)($[[REG_GP]])
+; CHECK:        lbu     $2, 0($[[REG_C_ADDR]])
+; CHECK:        jr      $ra
+}
+
+; Function Attrs: nounwind
 define signext i8 @retc() {
 entry:
 ; CHECK-LABEL: retc: