commit fa31e8f4a0f853848d96549a429083941877bf8d
Author: Sergei Trofimovich <siarheit@google.com>
Date:   Sun Dec 14 14:30:12 2014 +0000

    powerpc: fix and enable shared libraries by default on linux
    
    Summary:
    And fix things all the way down to it. Namely:
        - remove 'r30' from free registers, it's an .LCTOC1 register
          for gcc. generated .plt stubs expect it to be initialised.
        - fix PicBase computation, which originally forgot to use 'tmp'
          reg in 'initializePicBase_ppc.fetchPC'
        - mark 'ForeighTarget's as implicitly using 'PicBase' register
          (see comment for details)
        - add 64-bit MO_Sub and test on alloclimit3/4 regtests
        - fix dynamic label offsets to match with .LCTOC1 offset
    
    Signed-off-by: Sergei Trofimovich <siarheit@google.com>
    
    Test Plan: validate passes equal amount of vanilla/dyn tests
    
    Reviewers: simonmar, erikd, austin
    
    Reviewed By: erikd, austin
    
    Subscribers: carter, thomie
    
    Differential Revision: https://phabricator.haskell.org/D560
    
    GHC Trac Issues: #8024, #9831

diff --git a/compiler/cmm/CLabel.hs b/compiler/cmm/CLabel.hs
index 0f2c0ae..37b8ada 100644
--- a/compiler/cmm/CLabel.hs
+++ b/compiler/cmm/CLabel.hs
@@ -1170,7 +1170,8 @@ pprDynamicLinkerAsmLabel platform dllInfo lbl
    else if osElfTarget (platformOS platform)
         then if platformArch platform == ArchPPC
              then case dllInfo of
-                  CodeStub  -> ppr lbl <> text "@plt"
+                  CodeStub  -> -- See Note [.LCTOC1 in PPC PIC code]
+                               ppr lbl <> text "+32768@plt"
                   SymbolPtr -> text ".LC_" <> ppr lbl
                   _         -> panic "pprDynamicLinkerAsmLabel"
              else if platformArch platform == ArchX86_64
diff --git a/compiler/nativeGen/PIC.hs b/compiler/nativeGen/PIC.hs
index 9b5c080..6326a8b 100644
--- a/compiler/nativeGen/PIC.hs
+++ b/compiler/nativeGen/PIC.hs
@@ -54,7 +54,6 @@ import qualified X86.Instr      as X86
 
 import Platform
 import Instruction
-import Size
 import Reg
 import NCGMonad
 
@@ -468,11 +467,8 @@ pprGotDeclaration dflags ArchX86 OSDarwin
 pprGotDeclaration _ _ OSDarwin
         = empty
 
--- pprGotDeclaration
+-- Emit GOT declaration
 -- Output whatever needs to be output once per .s file.
--- The .LCTOC1 label is defined to point 32768 bytes into the table,
--- to make the most of the PPC's 16-bit displacements.
--- Only needed for PIC.
 pprGotDeclaration dflags arch os
         | osElfTarget os
         , arch  /= ArchPPC_64
@@ -482,6 +478,7 @@ pprGotDeclaration dflags arch os
         | osElfTarget os
         , arch  /= ArchPPC_64
         = vcat [
+                -- See Note [.LCTOC1 in PPC PIC code]
                 ptext (sLit ".section \".got2\",\"aw\""),
                 ptext (sLit ".LCTOC1 = .+32768") ]
 
@@ -688,12 +685,7 @@ pprImportedSymbol _ _ _
 
 
 -- Get a pointer to our own fake GOT, which is defined on a per-module basis.
--- This is exactly how GCC does it, and it's quite horrible:
--- We first fetch the address of a local label (mkPicBaseLabel).
--- Then we add a 16-bit offset to that to get the address of a .long that we
--- define in .text space right next to the proc. This .long literal contains
--- the (32-bit) offset from our local label to our global offset table
--- (.LCTOC1 aka gotOffLabel).
+-- This is exactly how GCC does it in linux.
 
 initializePicBase_ppc
         :: Arch -> OS -> Reg
@@ -704,18 +696,9 @@ initializePicBase_ppc ArchPPC os picReg
     (CmmProc info lab live (ListGraph blocks) : statics)
     | osElfTarget os
     = do
-        dflags <- getDynFlags
-        gotOffLabel <- getNewLabelNat
-        tmp <- getNewRegNat $ intSize (wordWidth dflags)
         let
-            gotOffset = CmmData Text $ Statics gotOffLabel [
-                            CmmStaticLit (CmmLabelDiffOff gotLabel
-                                                          mkPicBaseLabel
-                                                          0)
-                        ]
-            offsetToOffset
-                        = PPC.ImmConstantDiff
-                                (PPC.ImmCLbl gotOffLabel)
+            gotOffset = PPC.ImmConstantDiff
+                                (PPC.ImmCLbl gotLabel)
                                 (PPC.ImmCLbl mkPicBaseLabel)
 
             blocks' = case blocks of
@@ -726,15 +709,23 @@ initializePicBase_ppc ArchPPC os picReg
               | bID `mapMember` info = fetchPC b
               | otherwise            = b
 
+            -- GCC does PIC prologs thusly:
+            --     bcl 20,31,.L1
+            -- .L1:
+            --     mflr 30
+            --     addis 30,30,.LCTOC1-.L1@ha
+            --     addi 30,30,.LCTOC1-.L1@l
+            -- TODO: below we use it over temporary register,
+            -- it can and should be optimised by picking
+            -- correct PIC reg.
             fetchPC (BasicBlock bID insns) =
               BasicBlock bID (PPC.FETCHPC picReg
-                              : PPC.ADDIS tmp picReg (PPC.HI offsetToOffset)
-                              : PPC.LD PPC.archWordSize tmp
-                                   (PPC.AddrRegImm tmp (PPC.LO offsetToOffset))
-                              : PPC.ADD picReg picReg (PPC.RIReg picReg)
+                              : PPC.ADDIS picReg picReg (PPC.HA gotOffset)
+                              : PPC.ADDI picReg picReg (PPC.LO gotOffset)
+                              : PPC.MR PPC.r30 picReg
                               : insns)
 
-        return (CmmProc info lab live (ListGraph blocks') : gotOffset : statics)
+        return (CmmProc info lab live (ListGraph blocks') : statics)
 
 
 initializePicBase_ppc ArchPPC OSDarwin picReg
diff --git a/compiler/nativeGen/PPC/CodeGen.hs b/compiler/nativeGen/PPC/CodeGen.hs
index ddf483a..c1c4a74 100644
--- a/compiler/nativeGen/PPC/CodeGen.hs
+++ b/compiler/nativeGen/PPC/CodeGen.hs
@@ -54,7 +54,7 @@ import Outputable
 import Unique
 import DynFlags
 
-import Control.Monad    ( mapAndUnzipM )
+import Control.Monad    ( mapAndUnzipM, when )
 import Data.Bits
 import Data.Word
 
@@ -355,6 +355,19 @@ iselExpr64 (CmmMachOp (MO_Add _) [e1,e2]) = do
                        ADDE rhi r1hi r2hi ]
    return (ChildCode64 code rlo)
 
+iselExpr64 (CmmMachOp (MO_Sub _) [e1,e2]) = do
+   ChildCode64 code1 r1lo <- iselExpr64 e1
+   ChildCode64 code2 r2lo <- iselExpr64 e2
+   (rlo,rhi) <- getNewRegPairNat II32
+   let
+        r1hi = getHiVRegFromLo r1lo
+        r2hi = getHiVRegFromLo r2lo
+        code =  code1 `appOL`
+                code2 `appOL`
+                toOL [ SUBFC rlo r2lo r1lo,
+                       SUBFE rhi r2hi r1hi ]
+   return (ChildCode64 code rlo)
+
 iselExpr64 (CmmMachOp (MO_UU_Conv W32 W64) [expr]) = do
     (expr_reg,expr_code) <- getSomeReg expr
     (rlo, rhi) <- getNewRegPairNat II32
@@ -918,8 +931,12 @@ genCCall' dflags gcp target dest_regs args0
                                                         (toOL []) []
 
         (labelOrExpr, reduceToFF32) <- case target of
-            ForeignTarget (CmmLit (CmmLabel lbl)) _ -> return (Left lbl, False)
-            ForeignTarget expr _ -> return  (Right expr, False)
+            ForeignTarget (CmmLit (CmmLabel lbl)) _ -> do
+                uses_pic_base_implicitly
+                return (Left lbl, False)
+            ForeignTarget expr _ -> do
+                uses_pic_base_implicitly
+                return (Right expr, False)
             PrimTarget mop -> outOfLineMachOp mop
 
         let codeBefore = move_sp_down finalStack `appOL` passArgumentsCode
@@ -940,6 +957,13 @@ genCCall' dflags gcp target dest_regs args0
     where
         platform = targetPlatform dflags
 
+        uses_pic_base_implicitly = do
+            -- See Note [implicit register in PPC PIC code]
+            -- on why we claim to use PIC register here
+            when (gopt Opt_PIC dflags) $ do
+                _ <- getPicBaseNat archWordSize
+                return ()
+
         initialStackOffset = case gcp of
                              GCPDarwin -> 24
                              GCPLinux  -> 8
@@ -1431,3 +1455,21 @@ coerceFP2Int _ toRep x = do
                 -- read low word of value (high word is undefined)
             LD II32 dst (spRel dflags 3)]
     return (Any (intSize toRep) code')
+
+-- Note [.LCTOC1 in PPC PIC code]
+-- The .LCTOC1 label is defined to point 32768 bytes into the GOT table
+-- to make the most of the PPC's 16-bit displacements.
+-- As 16-bit signed offset is used (usually via addi/lwz instructions)
+-- first element will have '-32768' offset against .LCTOC1.
+
+-- Note [implicit register in PPC PIC code]
+-- PPC generates calls by labels in assembly
+-- in form of:
+--     bl puts+32768@plt
+-- in this form it's not seen directly (by GHC NCG)
+-- that r30 (PicBaseReg) is used,
+-- but r30 is a required part of PLT code setup:
+--   puts+32768@plt:
+--       lwz     r11,-30484(r30) ; offset in .LCTOC1
+--       mtctr   r11
+--       bctr
diff --git a/compiler/nativeGen/PPC/Instr.hs b/compiler/nativeGen/PPC/Instr.hs
index f5b9506..b7081f9 100644
--- a/compiler/nativeGen/PPC/Instr.hs
+++ b/compiler/nativeGen/PPC/Instr.hs
@@ -205,8 +205,11 @@ data Instr
     | ADD     Reg Reg RI            -- dst, src1, src2
     | ADDC    Reg Reg Reg           -- (carrying) dst, src1, src2
     | ADDE    Reg Reg Reg           -- (extend) dst, src1, src2
+    | ADDI    Reg Reg Imm           -- Add Immediate dst, src1, src2
     | ADDIS   Reg Reg Imm           -- Add Immediate Shifted dst, src1, src2
     | SUBF    Reg Reg Reg           -- dst, src1, src2 ; dst = src2 - src1
+    | SUBFC   Reg Reg Reg           -- (carrying) dst, src1, src2 ; dst = src2 - src1
+    | SUBFE   Reg Reg Reg           -- (extend) dst, src1, src2 ; dst = src2 - src1
     | MULLW   Reg Reg RI
     | DIVW    Reg Reg Reg
     | DIVWU   Reg Reg Reg
@@ -284,8 +287,11 @@ ppc_regUsageOfInstr platform instr
     ADD     reg1 reg2 ri     -> usage (reg2 : regRI ri, [reg1])
     ADDC    reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
     ADDE    reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
+    ADDI    reg1 reg2 _      -> usage ([reg2], [reg1])
     ADDIS   reg1 reg2 _      -> usage ([reg2], [reg1])
     SUBF    reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
+    SUBFC   reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
+    SUBFE   reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
     MULLW   reg1 reg2 ri     -> usage (reg2 : regRI ri, [reg1])
     DIVW    reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
     DIVWU   reg1 reg2 reg3   -> usage ([reg2,reg3], [reg1])
@@ -358,8 +364,11 @@ ppc_patchRegsOfInstr instr env
     ADD     reg1 reg2 ri    -> ADD (env reg1) (env reg2) (fixRI ri)
     ADDC    reg1 reg2 reg3  -> ADDC (env reg1) (env reg2) (env reg3)
     ADDE    reg1 reg2 reg3  -> ADDE (env reg1) (env reg2) (env reg3)
+    ADDI    reg1 reg2 imm   -> ADDI (env reg1) (env reg2) imm
     ADDIS   reg1 reg2 imm   -> ADDIS (env reg1) (env reg2) imm
     SUBF    reg1 reg2 reg3  -> SUBF (env reg1) (env reg2) (env reg3)
+    SUBFC   reg1 reg2 reg3  -> SUBFC (env reg1) (env reg2) (env reg3)
+    SUBFE   reg1 reg2 reg3  -> SUBFE (env reg1) (env reg2) (env reg3)
     MULLW   reg1 reg2 ri    -> MULLW (env reg1) (env reg2) (fixRI ri)
     DIVW    reg1 reg2 reg3  -> DIVW (env reg1) (env reg2) (env reg3)
     DIVWU   reg1 reg2 reg3  -> DIVWU (env reg1) (env reg2) (env reg3)
diff --git a/compiler/nativeGen/PPC/Ppr.hs b/compiler/nativeGen/PPC/Ppr.hs
index 6851769..f59d51f 100644
--- a/compiler/nativeGen/PPC/Ppr.hs
+++ b/compiler/nativeGen/PPC/Ppr.hs
@@ -525,6 +525,16 @@ pprInstr (BCTRL _) = hcat [
         ptext (sLit "bctrl")
     ]
 pprInstr (ADD reg1 reg2 ri) = pprLogic (sLit "add") reg1 reg2 ri
+pprInstr (ADDI reg1 reg2 imm) = hcat [
+        char '\t',
+        ptext (sLit "addi"),
+        char '\t',
+        pprReg reg1,
+        ptext (sLit ", "),
+        pprReg reg2,
+        ptext (sLit ", "),
+        pprImm imm
+    ]
 pprInstr (ADDIS reg1 reg2 imm) = hcat [
         char '\t',
         ptext (sLit "addis"),
@@ -539,6 +549,8 @@ pprInstr (ADDIS reg1 reg2 imm) = hcat [
 pprInstr (ADDC reg1 reg2 reg3) = pprLogic (sLit "addc") reg1 reg2 (RIReg reg3)
 pprInstr (ADDE reg1 reg2 reg3) = pprLogic (sLit "adde") reg1 reg2 (RIReg reg3)
 pprInstr (SUBF reg1 reg2 reg3) = pprLogic (sLit "subf") reg1 reg2 (RIReg reg3)
+pprInstr (SUBFC reg1 reg2 reg3) = pprLogic (sLit "subfc") reg1 reg2 (RIReg reg3)
+pprInstr (SUBFE reg1 reg2 reg3) = pprLogic (sLit "subfe") reg1 reg2 (RIReg reg3)
 pprInstr (MULLW reg1 reg2 ri@(RIReg _)) = pprLogic (sLit "mullw") reg1 reg2 ri
 pprInstr (MULLW reg1 reg2 ri@(RIImm _)) = pprLogic (sLit "mull") reg1 reg2 ri
 pprInstr (DIVW reg1 reg2 reg3) = pprLogic (sLit "divw") reg1 reg2 (RIReg reg3)
diff --git a/compiler/nativeGen/PPC/Regs.hs b/compiler/nativeGen/PPC/Regs.hs
index 0f636bf..69e69c0 100644
--- a/compiler/nativeGen/PPC/Regs.hs
+++ b/compiler/nativeGen/PPC/Regs.hs
@@ -37,7 +37,8 @@ module PPC.Regs (
         fits16Bits,
         makeImmediate,
         fReg,
-        sp, r3, r4, r27, r28, f1, f20, f21,
+        sp, r3, r4, r27, r28, r30,
+        f1, f20, f21,
 
         allocatableRegs
 
@@ -295,12 +296,13 @@ point registers.
 fReg :: Int -> RegNo
 fReg x = (32 + x)
 
-sp, r3, r4, r27, r28, f1, f20, f21 :: Reg
+sp, r3, r4, r27, r28, r30, f1, f20, f21 :: Reg
 sp      = regSingle 1
 r3      = regSingle 3
 r4      = regSingle 4
 r27     = regSingle 27
 r28     = regSingle 28
+r30     = regSingle 30
 f1      = regSingle $ fReg 1
 f20     = regSingle $ fReg 20
 f21     = regSingle $ fReg 21
diff --git a/includes/CodeGen.Platform.hs b/includes/CodeGen.Platform.hs
index 9916e0e..1d46a01 100644
--- a/includes/CodeGen.Platform.hs
+++ b/includes/CodeGen.Platform.hs
@@ -881,6 +881,8 @@ freeReg 1 = fastBool False -- The Stack Pointer
 # if !MACHREGS_darwin
 -- most non-darwin powerpc OSes use r2 as a TOC pointer or something like that
 freeReg 2 = fastBool False
+-- at least linux in -fPIC relies on r30 in PLT stubs
+freeReg 30 = fastBool False
 # endif
 # ifdef REG_Base
 freeReg REG_Base = fastBool False
diff --git a/mk/config.mk.in b/mk/config.mk.in
index 0f5820f..8f134bc 100644
--- a/mk/config.mk.in
+++ b/mk/config.mk.in
@@ -95,7 +95,7 @@ TargetElf = YES
 endif
 
 # Some platforms don't support shared libraries
-NoSharedLibsPlatformList = powerpc-unknown-linux \
+NoSharedLibsPlatformList = \
 	x86_64-unknown-mingw32 \
 	i386-unknown-mingw32