[wip][mips] Correct jal expansion for local symbols in .local directives.

[dsanders]

Summary

(off-list for now since it doesn't work correctly when -save-temps or
-via-file-asm are used. I'm not sure how to fix that yet.)

This patch corrects the behaviour of code such as:

  .local foo
  jal foo
foo:

to use the correct jal expansion but only when writing ELF files and not when
emitting assembly. The problem lies in the behaviour of MCAsmStreamer vs
MCELFStreamer. MCAsmStreamer emits a '.local foo' directive but doesn't update
the symbol in any way, while MCELFStreamer marks the symbol not-external and
sets the binding to STB_LOCAL.

[seanbruno]

I'll give this a spin today.

[seanbruno]

In combination with other FreeBSD specific patches, this looks good to me.

[seanbruno]

I'm content with this, do you want this to land?

[sdardis]

I'll take a look at this and see if I can resolve the issue Daniel mentioned.

[sdardis]

D24722 contains the updated version of this patch and posts it to the list.

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

if ((Inst.getOpcode() == Mips::JAL || Inst.getOpcode() == Mips::JAL_MM) &&
 
     // FIXME: This is checking the expression can be handled by the later stages
     //        of the assembler. We ought to leave it to those later stages.
     const MCSymbol *JalSym = getSingleMCSymbol(JalExpr);
 
     // FIXME: Add support for label+offset operands (currently causes an error).
     // FIXME: Add support for forward-declared local symbols.
     // FIXME: Add expansion for when the LargeGOT option is enabled.
-    if (JalSym->isInSection() || JalSym->isTemporary()) {
+    if (JalSym->isInSection() || JalSym->isTemporary() ||
+        (JalSym->isELF() && cast<MCSymbolELF>(JalSym)->getBinding() == ELF::STB_LOCAL)) {
       if (isABI_O32()) {
         // If it's a local symbol and the O32 ABI is being used, we expand to:
         //  lw $25, 0($gp)
         //    R_(MICRO)MIPS_GOT16  label
         //  addiu $25, $25, 0
         //    R_(MICRO)MIPS_LO16   label
         //  jalr  $25
         const MCExpr *Got16RelocExpr =

test/MC/Mips/expansion-jal-sym-pic.s

 # RUN:   FileCheck %s -check-prefixes=ALL,MICROMIPS,O32-MICROMIPS
 
 # RUN: llvm-mc %s -arch=mips64 -mcpu=mips64 -target-abi n32 -mattr=micromips -show-encoding |\
 # RUN:   FileCheck %s -check-prefixes=ALL,MICROMIPS,N32-MICROMIPS
 
 # RUN: llvm-mc %s -arch=mips64 -mcpu=mips64 -target-abi n64 -mattr=micromips -show-encoding |\
 # RUN:   FileCheck %s -check-prefixes=ALL,MICROMIPS,N64-MICROMIPS
 
+# Repeat the tests but using ELF output. Unfortunately, differences between
+# MCAsmStreamer and MCELFStreamer cause symbols (such as .text, and those
+# declared with .local) to be considered external when expanding the jal macro
+# and as such we have a discrepancy between assembly and ELF output that must
+# be fixed. This is very rarely a problem in practice since jal is fairly
+# uncommon. The only known example is FreeBSD's crt objects.
+# RUN: llvm-mc %s -arch=mips -mcpu=mips32 -filetype=obj | \
+# RUN:   llvm-objdump -d -r - | FileCheck %s -check-prefixes=ELF-O32
+# RUN: llvm-mc %s -arch=mips64 -mcpu=mips64 -target-abi n32 -filetype=obj | \
+# RUN:   llvm-objdump -d -r - | FileCheck %s -check-prefixes=ELF-N32
+# RUN: llvm-mc %s -arch=mips64 -mcpu=mips64 -target-abi n64 -filetype=obj | \
+# RUN:   llvm-objdump -d -r - | FileCheck %s -check-prefixes=ELF-N64
+
   .weak weak_label
 
   .text
   .option pic2
 
   .ent local_label
 local_label:
   .frame  $sp, 0, $ra
   .set noreorder
 
   jal local_label
   nop
 
-  jal weak_label
-  nop
-
-  jal global_label
-  nop
-
-  jal .text
-  nop
-
-  # local labels ($tmp symbols)
-  jal 1f
-  nop
-
-  .end local_label
-
-1:
-  nop
-  add $8, $8, $8
-  nop
-
 # Expanding "jal local_label":
 # O32: lw     $25, %got(local_label)($gp)   # encoding: [0x8f,0x99,A,A]
 # O32:                                      #   fixup A - offset: 0, value: %got(local_label), kind:   fixup_Mips_GOT
 # O32: addiu  $25, $25, %lo(local_label)    # encoding: [0x27,0x39,A,A]
 # O32:                                      #   fixup A - offset: 0, value: %lo(local_label), kind:   fixup_Mips_LO16
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_GOT16 .text
+# ELF-O32-NEXT: 27 39 00 00 addiu $25, $25, 0
+# ELF-O32-NEXT:                 R_MIPS_LO16 .text
 
 # N32: lw  $25, %got_disp(local_label)($gp) # encoding: [0x8f,0x99,A,A]
 # N32:                                      #   fixup A - offset: 0, value: %got_disp(local_label), kind:   fixup_Mips_GOT_DISP
 
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE local_label
+
 # N64: ld  $25, %got_disp(local_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64:                                      #   fixup A - offset: 0, value: %got_disp(local_label), kind:   fixup_Mips_GOT_DISP
 
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE local_label
+
 # O32-MICROMIPS: lw    $25, %got(local_label)($gp)      # encoding: [0xff,0x3c,A,A]
 # O32-MICROMIPS:                                        #   fixup A - offset: 0, value: %got(local_label), kind:   fixup_MICROMIPS_GOT16
 # O32-MICROMIPS: addiu $25, $25, %lo(local_label)       # encoding: [0x33,0x39,A,A]
 # O32-MICROMIPS:                                        #   fixup A - offset: 0, value: %lo(local_label), kind:   fixup_MICROMIPS_LO16
 
 # N32-MICROMIPS: lw    $25, %got_disp(local_label)($gp) # encoding: [0xff,0x3c,A,A]
 # N32-MICROMIPS:                                        #   fixup A - offset: 0, value: %got_disp(local_label), kind: fixup_MICROMIPS_GOT_DISP
 
 # N64-MICROMIPS: ld    $25, %got_disp(local_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64-MICROMIPS:                                        #   fixup A - offset: 0, value: %got_disp(local_label), kind: fixup_MICROMIPS_GOT_DISP
 
 # NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
 # MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
 # ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
 
+  jal weak_label
+  nop
 
 # Expanding "jal weak_label":
 # O32: lw  $25, %call16(weak_label)($gp) # encoding: [0x8f,0x99,A,A]
 # O32:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind:   fixup_Mips_CALL16
 
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_CALL16 weak_label
+
 # N32: lw  $25, %call16(weak_label)($gp) # encoding: [0x8f,0x99,A,A]
 # N32:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind:   fixup_Mips_CALL16
 
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE weak_label
+
 # N64: ld  $25, %call16(weak_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind:   fixup_Mips_CALL16
 
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE weak_label
+
 # O32-MICROMIPS: lw  $25, %call16(weak_label)($gp) # encoding: [0xff,0x3c,A,A]
 # O32-MICROMIPS:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind:   fixup_MICROMIPS_CALL16
 
 # N32-MICROMIPS: lw  $25, %call16(weak_label)($gp) # encoding: [0xff,0x3c,A,A]
 # N32-MICROMIPS:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind: fixup_MICROMIPS_CALL16
 
 # N64-MICROMIPS: ld  $25, %call16(weak_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64-MICROMIPS:                                   #   fixup A - offset: 0, value: %call16(weak_label), kind: fixup_MICROMIPS_CALL16
 
 # NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
 # MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
 # ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
 
+  jal global_label
+  nop
 
 # Expanding "jal global_label":
 # O32: lw  $25, %call16(global_label)($gp) # encoding: [0x8f,0x99,A,A]
 # O32:                                     #   fixup A - offset: 0, value: %call16(global_label), kind:   fixup_Mips_CALL16
 
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_CALL16 global_label
+
 # N32: lw  $25, %call16(global_label)($gp) # encoding: [0x8f,0x99,A,A]
 # N32:                                     #   fixup A - offset: 0, value: %call16(global_label), kind:   fixup_Mips_CALL16
 
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE global_label
+
 # N64: ld  $25, %call16(global_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64:                                     #   fixup A - offset: 0, value: %call16(global_label), kind:   fixup_Mips_CALL16
 
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE global_label
+
 # O32-MICROMIPS: lw  $25, %call16(global_label)($gp) # encoding: [0xff,0x3c,A,A]
 # O32-MICROMIPS:                                     #   fixup A - offset: 0, value: %call16(global_label), kind: fixup_MICROMIPS_CALL16
 
 # N32-MICROMIPS: lw  $25, %call16(global_label)($gp) # encoding: [0xff,0x3c,A,A]
 # N32-MICROMIPS:                                     #   fixup A - offset: 0, value: %call16(global_label), kind: fixup_MICROMIPS_CALL16
 
 # N64-MICROMIPS: ld  $25, %call16(global_label)($gp) # encoding: [0xdf,0x99,A,A]
 # N64-MICROMIPS:                                     #   fixup A - offset: 0, value: %call16(global_label), kind: fixup_MICROMIPS_CALL16
 
 # NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
 # MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
 # ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
 
+  jal .text
+  nop
 
 # FIXME: The .text section MCSymbol isn't created when printing assembly. However,
 # it is created when generating an ELF object file.
 # Expanding "jal .text":
-# O32-FIXME: lw    $25, %got(.text)($gp)           # encoding: [0x8f,0x99,A,A]
-# O32-FIXME:                                       #   fixup A - offset: 0, value: %got(.text), kind: fixup_Mips_GOT
-# O32-FIXME: addiu $25, $25, %lo(.text)            # encoding: [0x27,0x39,A,A]
-# O32-FIXME:                                       #   fixup A - offset: 0, value: %lo(.text), kind: fixup_Mips_LO16
+# O32-FIXME: lw    $25, %call16(.text)($gp)        # encoding: [0x8f,0x99,A,A]
+# O32-FIXME:                                       #   fixup A - offset: 0, value: %got(.text), kind: fixup_Mips_GOT_CALL
 
-# N32-FIXME: lw  $25, %got_disp(.text)($gp)        # encoding: [0x8f,0x99,A,A]
-# N32-FIXME:                                       #   fixup A - offset: 0, value: %got_disp(.text), kind: fixup_Mips_GOT_DISP
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_CALL16 .text
 
-# N64-FIXME: ld  $25, %got_disp(.text)($gp)        # encoding: [0xdf,0x99,A,A]
-# N64-FIXME:                                       #   fixup A - offset: 0, value: %got_disp(.text), kind: fixup_Mips_GOT_DISP
+# N32-FIXME: lw  $25, %call16(.text)($gp)          # encoding: [0x8f,0x99,A,A]
+# N32-FIXME:                                       #   fixup A - offset: 0, value: %call16(.text), kind: fixup_Mips_GOT_DISP
+
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE .text
+
+# N64-FIXME: ld  $25, %call16(.text)($gp)          # encoding: [0xdf,0x99,A,A]
+# N64-FIXME:                                       #   fixup A - offset: 0, value: %call16(.text), kind: fixup_Mips_GOT_DISP
+
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_CALL16/R_MIPS_NONE/R_MIPS_NONE .text
 
 # O32-MICROMIPS-FIXME: lw    $25, %got(.text)($gp)      # encoding: [0xff,0x3c,A,A]
 # O32-MICROMIPS-FIXME:                                  #   fixup A - offset: 0, value: %got(.text), kind: fixup_MICROMIPS_GOT16
 # O32-MICROMIPS-FIXME: addiu $25, $25, %lo(.text)       # encoding: [0x33,0x39,A,A]
 # O32-MICROMIPS-FIXME:                                  #   fixup A - offset: 0, value: %lo(.text), kind: fixup_MICROMIPS_LO16
 
 # N32-MICROMIPS-FIXME: lw    $25, %got_disp(.text)($gp) # encoding: [0xff,0x3c,A,A]
 # N32-MICROMIPS-FIXME:                                  #   fixup A - offset: 0, value: %got_disp(.text), kind: fixup_MICROMIPS_GOT_DISP
 
 # N64-MICROMIPS-FIXME: ld    $25, %got_disp(.text)($gp) # encoding: [0xdf,0x99,A,A]
 # N64-MICROMIPS-FIXME:                                  #   fixup A - offset: 0, value: %got_disp(.text), kind: fixup_MICROMIPS_GOT_DISP
 
 # NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
 # MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
 # ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
 
+  # local labels ($tmp symbols)
+  jal 1f
+  nop
 
 # Expanding "jal 1f":
 # O32: lw     $25, %got($tmp0)($gp)   # encoding: [0x8f,0x99,A,A]
 # O32:                                #   fixup A - offset: 0, value: %got($tmp0), kind:   fixup_Mips_GOT
 # O32: addiu  $25, $25, %lo($tmp0)    # encoding: [0x27,0x39,A,A]
 # O32:                                #   fixup A - offset: 0, value: %lo($tmp0), kind:   fixup_Mips_LO16
 
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_GOT16 .text
+# ELF-O32-NEXT: 27 39 00 54 addiu $25, $25, 84
+# ELF-O32-NEXT:                 R_MIPS_LO16 .text
+
 # N32: lw  $25, %got_disp($tmp0)($gp) # encoding: [0x8f,0x99,A,A]
 # N32:                                #   fixup A - offset: 0, value: %got_disp($tmp0), kind:   fixup_Mips_GOT_DISP
 
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE .Ltmp0
+
 # N64: ld  $25, %got_disp(.Ltmp0)($gp) # encoding: [0xdf,0x99,A,A]
 # N64:                                 #   fixup A - offset: 0, value: %got_disp(.Ltmp0), kind:   fixup_Mips_GOT_DISP
 
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE .Ltmp0
+
 # O32-MICROMIPS: lw    $25, %got($tmp0)($gp)    # encoding: [0xff,0x3c,A,A]
 # O32-MICROMIPS:                                #   fixup A - offset: 0, value: %got($tmp0), kind: fixup_MICROMIPS_GOT16
 # O32-MICROMIPS: addiu $25, $25, %lo($tmp0)     # encoding: [0x33,0x39,A,A]
 # O32-MICROMIPS:                                #   fixup A - offset: 0, value: %lo($tmp0), kind: fixup_MICROMIPS_LO16
 
 # N32-MICROMIPS: lw  $25, %got_disp(.Ltmp0)($gp) # encoding: [0xff,0x3c,A,A]
 # N32-MICROMIPS:                                 #   fixup A - offset: 0, value: %got_disp(.Ltmp0), kind: fixup_MICROMIPS_GOT_DISP
 
 # N64-MICROMIPS: ld  $25, %got_disp(.Ltmp0)($gp) # encoding: [0xdf,0x99,A,A]
 # N64-MICROMIPS:                                 #   fixup A - offset: 0, value: %got_disp(.Ltmp0), kind: fixup_MICROMIPS_GOT_DISP
 
 # NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
 # MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
 # ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
+
+  .local forward_local
+  jal forward_local
+  nop
+
+# Expanding "jal forward_local":
+# O32-FIXME: lw     $25, %got(forward_local)($gp)   # encoding: [0x8f,0x99,A,A]
+# O32-FIXME:                                        #   fixup A - offset: 0, value: %got(forward_local), kind:   fixup_Mips_GOT
+# O32-FIXME: addiu  $25, $25, %lo(forward_local)    # encoding: [0x27,0x39,A,A]
+# O32-FIXME:                                        #   fixup A - offset: 0, value: %lo(forward_local), kind:   fixup_Mips_LO16
+
+# ELF-O32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-O32-NEXT:                 R_MIPS_GOT16 .text
+# ELF-O32-NEXT: 27 39 00 60 addiu $25, $25, 96
+# ELF-O32-NEXT:                 R_MIPS_LO16 .text
+
+# N32-FIXME: lw  $25, %got_disp(forward_local)($gp) # encoding: [0x8f,0x99,A,A]
+# N32-FIXME:                                        #   fixup A - offset: 0, value: %got_disp(forward_local), kind:   fixup_Mips_GOT_DISP
+
+# ELF-N32:      8f 99 00 00 lw $25, 0($gp)
+# ELF-N32-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE forward_local
+
+# N64-FIXME: ld  $25, %got_disp(forward_local)($gp) # encoding: [0xdf,0x99,A,A]
+# N64-FIXME:                                        #   fixup A - offset: 0, value: %got_disp(forward_local), kind:   fixup_Mips_GOT_DISP
+
+# ELF-N64:      df 99 00 00 ld $25, 0($gp)
+# ELF-N64-NEXT:                 R_MIPS_GOT_DISP/R_MIPS_NONE/R_MIPS_NONE forward_local
+
+# O32-MICROMIPS-FIXME: lw    $25, %got(forward_local)($gp)      # encoding: [0xff,0x3c,A,A]
+# O32-MICROMIPS-FIXME:                                          #   fixup A - offset: 0, value: %got(forward_local), kind:   fixup_MICROMIPS_GOT16
+# O32-MICROMIPS-FIXME: addiu $25, $25, %lo(forward_local)       # encoding: [0x33,0x39,A,A]
+# O32-MICROMIPS-FIXME:                                          #   fixup A - offset: 0, value: %lo(forward_local), kind:   fixup_MICROMIPS_LO16
+
+# N32-MICROMIPS-FIXME: lw    $25, %got_disp(forward_local)($gp) # encoding: [0xff,0x3c,A,A]
+# N32-MICROMIPS-FIXME:                                          #   fixup A - offset: 0, value: %got_disp(forward_local), kind: fixup_MICROMIPS_GOT_DISP
+
+# N64-MICROMIPS-FIXME: ld    $25, %got_disp(forward_local)($gp) # encoding: [0xdf,0x99,A,A]
+# N64-MICROMIPS-FIXME:                                          #   fixup A - offset: 0, value: %got_disp(forward_local), kind: fixup_MICROMIPS_GOT_DISP
+
+# NORMAL:    jalr $25      # encoding: [0x03,0x20,0xf8,0x09]
+# MICROMIPS: jalr $ra, $25 # encoding: [0x03,0xf9,0x0f,0x3c]
+# ALL:       nop           # encoding: [0x00,0x00,0x00,0x00]
+
+
+  .end local_label
+
+1:
+  nop
+  add $8, $8, $8
+  nop
+forward_local:
+