Add support for producing position-independent executables

Previously due to #12759 we disabled PIE support entirely. However, this
breaks the user's ability to produce PIEs. Add an explicit flag, -fPIE,
allowing the user to build PIEs.

Test Plan: Validate

Reviewers: rwbarton, austin, simonmar

Subscribers: trommler, simonmar, trofi, jrtc27, thomie

GHC Trac Issues: #12759, #13702

Differential Revision: https://phabricator.haskell.org/D3589

5 files changed, 26 insertions, 25 deletions

diff --git a/compiler/nativeGen/AsmCodeGen.hs b/compiler/nativeGen/AsmCodeGen.hs
index 45d170e28d..314d726b50 100644
--- a/compiler/nativeGen/AsmCodeGen.hs
+++ b/compiler/nativeGen/AsmCodeGen.hs
@@ -1212,15 +1212,15 @@ cmmExprNative referenceKind expr = do
         -- to use the register table, so we replace these registers
         -- with the corresponding labels:
         CmmReg (CmmGlobal EagerBlackholeInfo)
-          | arch == ArchPPC && not (gopt Opt_PIC dflags)
+          | arch == ArchPPC && not (positionIndependent dflags)
           -> cmmExprNative referenceKind $
              CmmLit (CmmLabel (mkCmmCodeLabel rtsUnitId (fsLit "__stg_EAGER_BLACKHOLE_info")))
         CmmReg (CmmGlobal GCEnter1)
-          | arch == ArchPPC && not (gopt Opt_PIC dflags)
+          | arch == ArchPPC && not (positionIndependent dflags)
           -> cmmExprNative referenceKind $
              CmmLit (CmmLabel (mkCmmCodeLabel rtsUnitId (fsLit "__stg_gc_enter_1")))
         CmmReg (CmmGlobal GCFun)
-          | arch == ArchPPC && not (gopt Opt_PIC dflags)
+          | arch == ArchPPC && not (positionIndependent dflags)
           -> cmmExprNative referenceKind $
              CmmLit (CmmLabel (mkCmmCodeLabel rtsUnitId (fsLit "__stg_gc_fun")))
 
diff --git a/compiler/nativeGen/PIC.hs b/compiler/nativeGen/PIC.hs
index bef0a21235..de1fbaa8d4 100644
--- a/compiler/nativeGen/PIC.hs
+++ b/compiler/nativeGen/PIC.hs
@@ -176,7 +176,7 @@ cmmMakePicReference dflags lbl
                                 (platformOS     $ targetPlatform dflags)
                                 lbl ]
 
-        | (gopt Opt_PIC dflags || WayDyn `elem` ways dflags) && absoluteLabel lbl
+        | (positionIndependent dflags || WayDyn `elem` ways dflags) && absoluteLabel lbl
         = CmmMachOp (MO_Add (wordWidth dflags))
                 [ CmmReg (CmmGlobal PicBaseReg)
                 , CmmLit $ picRelative
@@ -272,7 +272,7 @@ howToAccessLabel dflags arch OSDarwin this_mod DataReference lbl
         -- we'd need to pass the current Module all the way in to
         -- this function.
         | arch /= ArchX86_64
-        , gopt Opt_PIC dflags && externallyVisibleCLabel lbl
+        , positionIndependent dflags && externallyVisibleCLabel lbl
         = AccessViaSymbolPtr
 
         | otherwise
@@ -313,8 +313,8 @@ howToAccessLabel _dflags _arch OSAIX _this_mod kind _lbl
 --
 -- ELF tries to pretend to the main application code that dynamic linking does
 -- not exist. While this may sound convenient, it tends to mess things up in
--- very bad ways, so we have to be careful when we generate code for the main
--- program (-dynamic but no -fPIC).
+-- very bad ways, so we have to be careful when we generate code for a non-PIE
+-- main program (-dynamic but no -fPIC).
 --
 -- Indirect access is required for references to imported symbols
 -- from position independent code. It is also required from the main program
@@ -337,7 +337,7 @@ howToAccessLabel dflags _ os _ _ _
         --           if we don't dynamically link to Haskell code,
         --           it actually manages to do so without messing things up.
         | osElfTarget os
-        , not (gopt Opt_PIC dflags) && WayDyn `notElem` ways dflags
+        , not (positionIndependent dflags) && WayDyn `notElem` ways dflags
         = AccessDirectly
 
 howToAccessLabel dflags arch os this_mod DataReference lbl
@@ -351,7 +351,7 @@ howToAccessLabel dflags arch os this_mod DataReference lbl
             -- via a symbol pointer (see below for an explanation why
             -- PowerPC32 Linux is especially broken).
             | arch == ArchPPC
-            , gopt Opt_PIC dflags
+            , positionIndependent dflags
             -> AccessViaSymbolPtr
 
             | otherwise
@@ -372,12 +372,13 @@ howToAccessLabel dflags arch os this_mod DataReference lbl
 
 howToAccessLabel dflags arch os this_mod CallReference lbl
         | osElfTarget os
-        , labelDynamic dflags this_mod lbl && not (gopt Opt_PIC dflags)
+        , labelDynamic dflags this_mod lbl && not (positionIndependent dflags)
         = AccessDirectly
 
         | osElfTarget os
         , arch /= ArchX86
-        , labelDynamic dflags this_mod lbl && gopt Opt_PIC dflags
+        , labelDynamic dflags this_mod lbl
+        , positionIndependent dflags
         = AccessViaStub
 
 howToAccessLabel dflags _ os this_mod _ lbl
@@ -388,7 +389,7 @@ howToAccessLabel dflags _ os this_mod _ lbl
 
 -- all other platforms
 howToAccessLabel dflags _ _ _ _ _
-        | not (gopt Opt_PIC dflags)
+        | not (positionIndependent dflags)
         = AccessDirectly
 
         | otherwise
@@ -467,7 +468,7 @@ needImportedSymbols dflags arch os
         -- PowerPC Linux: -fPIC or -dynamic
         | osElfTarget os
         , arch  == ArchPPC
-        = gopt Opt_PIC dflags || WayDyn `elem` ways dflags
+        = positionIndependent dflags || WayDyn `elem` ways dflags
 
         -- PowerPC 64 Linux: always
         | osElfTarget os
@@ -477,7 +478,7 @@ needImportedSymbols dflags arch os
         -- i386 (and others?): -dynamic but not -fPIC
         | osElfTarget os
         , arch /= ArchPPC_64 ELF_V1 && arch /= ArchPPC_64 ELF_V2
-        = WayDyn `elem` ways dflags && not (gopt Opt_PIC dflags)
+        = WayDyn `elem` ways dflags && not (positionIndependent dflags)
 
         | otherwise
         = False
@@ -499,7 +500,7 @@ gotLabel
 -- However, for PIC on x86, we need a small helper function.
 pprGotDeclaration :: DynFlags -> Arch -> OS -> SDoc
 pprGotDeclaration dflags ArchX86 OSDarwin
-        | gopt Opt_PIC dflags
+        | positionIndependent dflags
         = vcat [
                 text ".section __TEXT,__textcoal_nt,coalesced,no_toc",
                 text ".weak_definition ___i686.get_pc_thunk.ax",
@@ -540,7 +541,7 @@ pprGotDeclaration _ (ArchPPC_64 _) _
 pprGotDeclaration dflags arch os
         | osElfTarget os
         , arch /= ArchPPC_64 ELF_V1 && arch /= ArchPPC_64 ELF_V2
-        , not (gopt Opt_PIC dflags)
+        , not (positionIndependent dflags)
         = empty
 
         | osElfTarget os
@@ -565,7 +566,7 @@ pprGotDeclaration _ _ _
 pprImportedSymbol :: DynFlags -> Platform -> CLabel -> SDoc
 pprImportedSymbol dflags platform@(Platform { platformArch = ArchPPC, platformOS = OSDarwin }) importedLbl
         | Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
-        = case gopt Opt_PIC dflags of
+        = case positionIndependent dflags of
            False ->
             vcat [
                 text ".symbol_stub",
@@ -619,7 +620,7 @@ pprImportedSymbol dflags platform@(Platform { platformArch = ArchPPC, platformOS
 
 pprImportedSymbol dflags platform@(Platform { platformArch = ArchX86, platformOS = OSDarwin }) importedLbl
         | Just (CodeStub, lbl) <- dynamicLinkerLabelInfo importedLbl
-        = case gopt Opt_PIC dflags of
+        = case positionIndependent dflags of
            False ->
             vcat [
                 text ".symbol_stub",
@@ -652,7 +653,7 @@ pprImportedSymbol dflags platform@(Platform { platformArch = ArchX86, platformOS
                     text "\tjmp dyld_stub_binding_helper"
             ]
           $+$ vcat [        text ".section __DATA, __la_sym_ptr"
-                    <> (if gopt Opt_PIC dflags then int 2 else int 3)
+                    <> (if positionIndependent dflags then int 2 else int 3)
                     <> text ",lazy_symbol_pointers",
                 text "L" <> pprCLabel platform lbl <> ptext (sLit "$lazy_ptr:"),
                     text "\t.indirect_symbol" <+> pprCLabel platform lbl,
diff --git a/compiler/nativeGen/PPC/CodeGen.hs b/compiler/nativeGen/PPC/CodeGen.hs
index 1e88a1d025..1a802d34b2 100644
--- a/compiler/nativeGen/PPC/CodeGen.hs
+++ b/compiler/nativeGen/PPC/CodeGen.hs
@@ -1598,7 +1598,7 @@ genCCall' dflags gcp target dest_regs args
         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 && target32Bit platform) $ do
+            when (positionIndependent dflags && target32Bit platform) $ do
                 _ <- getPicBaseNat $ archWordFormat True
                 return ()
 
@@ -1950,7 +1950,7 @@ genSwitch dflags expr targets
                     ]
         return code
 
-  | (gopt Opt_PIC dflags) || (not $ target32Bit $ targetPlatform dflags)
+  | (positionIndependent dflags) || (not $ target32Bit $ targetPlatform dflags)
   = do
         (reg,e_code) <- getSomeReg (cmmOffset dflags expr offset)
         let fmt = archWordFormat $ target32Bit $ targetPlatform dflags
@@ -1988,7 +1988,7 @@ generateJumpTableForInstr :: DynFlags -> Instr
                           -> Maybe (NatCmmDecl CmmStatics Instr)
 generateJumpTableForInstr dflags (BCTR ids (Just lbl)) =
     let jumpTable
-            | (gopt Opt_PIC dflags)
+            | (positionIndependent dflags)
               || (not $ target32Bit $ targetPlatform dflags)
             = map jumpTableEntryRel ids
             | otherwise = map (jumpTableEntry dflags) ids
diff --git a/compiler/nativeGen/SPARC/CodeGen.hs b/compiler/nativeGen/SPARC/CodeGen.hs
index 71d320fa63..72e25b945f 100644
--- a/compiler/nativeGen/SPARC/CodeGen.hs
+++ b/compiler/nativeGen/SPARC/CodeGen.hs
@@ -313,7 +313,7 @@ genCondJump bid bool = do
 
 genSwitch :: DynFlags -> CmmExpr -> SwitchTargets -> NatM InstrBlock
 genSwitch dflags expr targets
-        | gopt Opt_PIC dflags
+        | positionIndependent dflags
         = error "MachCodeGen: sparc genSwitch PIC not finished\n"
 
         | otherwise
diff --git a/compiler/nativeGen/X86/CodeGen.hs b/compiler/nativeGen/X86/CodeGen.hs
index bd4774ae2c..8f7fbd292b 100644
--- a/compiler/nativeGen/X86/CodeGen.hs
+++ b/compiler/nativeGen/X86/CodeGen.hs
@@ -2696,7 +2696,7 @@ outOfLineCmmOp mop res args
 genSwitch :: DynFlags -> CmmExpr -> SwitchTargets -> NatM InstrBlock
 
 genSwitch dflags expr targets
-  | gopt Opt_PIC dflags
+  | positionIndependent dflags
   = do
         (reg,e_code) <- getNonClobberedReg (cmmOffset dflags expr offset)
            -- getNonClobberedReg because it needs to survive across t_code
@@ -2759,7 +2759,7 @@ createJumpTable :: DynFlags -> [Maybe BlockId] -> Section -> CLabel
                 -> GenCmmDecl (Alignment, CmmStatics) h g
 createJumpTable dflags ids section lbl
     = let jumpTable
-            | gopt Opt_PIC dflags =
+            | positionIndependent dflags =
                   let jumpTableEntryRel Nothing
                           = CmmStaticLit (CmmInt 0 (wordWidth dflags))
                       jumpTableEntryRel (Just blockid)