[mips][mips64r6] Use JALR for returns instead of JR (which is not available on MIPS32r6/MIPS64r6)

Summary:
RET, and RET_MM have been replaced by a pseudo named PseudoReturn.
In addition a version with a 64-bit GPR named PseudoReturn64 has been
added.

Instruction selection for a return matches RetRA, which is expanded post
register allocation to PseudoReturn/PseudoReturn64. During MipsAsmPrinter,
this PseudoReturn/PseudoReturn64 are emitted as:
- (JALR64 $zero, $rs) on MIPS64r6
- (JALR $zero, $rs) on MIPS32r6
- (JR_MM $rs) on microMIPS
- (JR $rs) otherwise

On MIPS32r6/MIPS64r6, 'jr $rs' is an alias for 'jalr $zero, $rs'. To aid
development and review (specifically, to ensure all cases of jr are
updated), these aliases are temporarily named 'r6.jr' instead of 'jr'.
A follow up patch will change them back to the correct mnemonic.

Added (JALR $zero, $rs) to MipsNaClELFStreamer's definition of an indirect
jump, and removed it from its definition of a call.
Note: I haven't accounted for MIPS64 in MipsNaClELFStreamer since it's
doesn't appear to account for any MIPS64-specifics.

The return instruction created as part of eh_return expansion is now expanded
using expandRetRA() so we use the right return instruction on MIPS32r6/MIPS64r6
('jalr $zero, $rs').

Also, fixed a misuse of isABI_N64() to detect 64-bit wide registers in
expandEhReturn().

Reviewers: jkolek, vmedic, mseaborn, zoran.jovanovic, dsanders

Reviewed By: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D4268


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212604 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/Mips/eh-return32.ll

@@ -1,4 +1,6 @@
-; RUN: llc -march=mipsel -mcpu=mips32 < %s | FileCheck %s
+; RUN: llc -march=mipsel -mcpu=mips32   -asm-show-inst < %s | FileCheck %s -check-prefix=CHECK -check-prefix=NOT-R6
+; RUN: llc -march=mipsel -mcpu=mips32r2 -asm-show-inst < %s | FileCheck %s -check-prefix=CHECK -check-prefix=NOT-R6
+; RUN: llc -march=mipsel -mcpu=mips32r6 -asm-show-inst < %s | FileCheck %s -check-prefix=CHECK -check-prefix=R6
 
 declare void @llvm.eh.return.i32(i32, i8*)
 declare void @foo(...)
@@ -9,7 +11,7 @@ entry:
   call void @llvm.eh.return.i32(i32 %offset, i8* %handler)
   unreachable
 
-; CHECK:        f1
+; CHECK:    f1:
 ; CHECK:        addiu   $sp, $sp, -[[spoffset:[0-9]+]]
 
 ; check that $a0-$a3 are saved on stack.
@@ -41,7 +43,8 @@ entry:
 ; CHECK:        addiu   $sp, $sp, [[spoffset]]
 ; CHECK:        move    $25, $2
 ; CHECK:        move    $ra, $2
-; CHECK:        jr      $ra
+; NOT-R6:       jr      $ra # <MCInst #{{[0-9]+}} JR
+; R6:           jr      $ra # <MCInst #{{[0-9]+}} JALR
 ; CHECK:        addu    $sp, $sp, $3
 }
 
@@ -50,7 +53,7 @@ entry:
   call void @llvm.eh.return.i32(i32 %offset, i8* %handler)
   unreachable
 
-; CHECK:        f2
+; CHECK:    f2:
 ; CHECK:        addiu   $sp, $sp, -[[spoffset:[0-9]+]]
 
 ; check that $a0-$a3 are saved on stack.
@@ -80,6 +83,7 @@ entry:
 ; CHECK:        addiu   $sp, $sp, [[spoffset]]
 ; CHECK:        move    $25, $2
 ; CHECK:        move    $ra, $2
-; CHECK:        jr      $ra
+; NOT-R6:       jr      $ra # <MCInst #{{[0-9]+}} JR
+; R6:           jr      $ra # <MCInst #{{[0-9]+}} JALR
 ; CHECK:        addu    $sp, $sp, $3
 }