Remove dynamic-by-default (#16782)

Dynamic-by-default was a mechanism to automatically select the -dynamic
way for some targets.

It was implemented in a convoluted way: it was defined as a flavour
option, hence it couldn't be passed as a global settings (which are
produced by `configure` before considering flavours), so a build system
rule was used to pass -DDYNAMIC_BY_DEFAULT to the C compiler so that
deriveConstants could infer it.

* Make build system has it disabled for 8 years (951e28c0625ece7e0db6ac9d4a1e61e2737b10de)
* It has never been implemented in Hadrian
* Last time someone tried to enable it 1 year ago it didn't work (!2436)
* Having this as a global constant impedes making GHC multi-target (see !5427)

This commit fully removes support for dynamic-by-default. If someone
wants to reimplement something like this, it would probably need to move
the logic in the compiler.

(Doing this would probably need some refactoring of the way the compiler
handles DynFlags: DynFlags are used to store and to pass enabled ways to
many parts of the compiler. It can be set by command-line flags, GHC
API, global settings. In multi-target GHC, we will use DynFlags to load
the target platform and its constants: but at this point with the
current DynFlags implementation we can't easily update the existing
DynFlags with target-specific options such as dynamic-by-default without
overriding ways previously set by the user.)

18 files changed, 6 insertions, 72 deletions

diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index c1142137cc..ce26b0e984 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -148,7 +148,6 @@ module GHC.Driver.Session (
         -- ** Manipulating DynFlags
         addPluginModuleName,
         defaultDynFlags,                -- Settings -> DynFlags
-        defaultWays,
         initDynFlags,                   -- DynFlags -> IO DynFlags
         defaultFatalMessager,
         defaultFlushOut,
@@ -1173,7 +1172,7 @@ defaultDynFlags mySettings llvmConfig =
         ignorePackageFlags      = [],
         trustFlags              = [],
         packageEnv              = Nothing,
-        targetWays_             = defaultWays mySettings,
+        targetWays_             = Set.empty,
         splitInfo               = Nothing,
 
         ghcNameVersion = sGhcNameVersion mySettings,
@@ -1255,12 +1254,6 @@ defaultDynFlags mySettings llvmConfig =
         cfgWeights    = defaultWeights
       }
 
-defaultWays :: Settings -> Ways
-defaultWays settings = if pc_DYNAMIC_BY_DEFAULT (sPlatformConstants settings)
-                       then Set.singleton WayDyn
-                       else Set.empty
-
-
 type FatalMessager = String -> IO ()
 
 defaultFatalMessager :: FatalMessager
@@ -3652,7 +3645,6 @@ defaultFlags settings
 
     ++ default_RPath platform
 
-    ++ concatMap (wayGeneralFlags platform) (defaultWays settings)
     ++ validHoleFitDefaults
 
     where platform = sTargetPlatform settings
@@ -4677,8 +4669,6 @@ compilerInfo dflags
        ("Uses package keys",           "YES"),
        -- Whether or not we support the @-this-unit-id@ flag
        ("Uses unit IDs",               "YES"),
-       -- Whether or not GHC compiles libraries as dynamic by default
-       ("Dynamic by default",          showBool $ pc_DYNAMIC_BY_DEFAULT constants),
        -- Whether or not GHC was compiled using -dynamic
        ("GHC Dynamic",                 showBool hostIsDynamic),
        -- Whether or not GHC was compiled using -prof
@@ -4692,7 +4682,6 @@ compilerInfo dflags
     showBool True  = "YES"
     showBool False = "NO"
     platform  = targetPlatform dflags
-    constants = platformConstants platform
     isWindows = platformOS platform == OSMinGW32
     expandDirectories :: FilePath -> Maybe FilePath -> String -> String
     expandDirectories topd mtoold = expandToolDir mtoold . expandTopDir topd
diff --git a/hadrian/src/Oracles/TestSettings.hs b/hadrian/src/Oracles/TestSettings.hs
index ba89e00beb..b5f197299b 100644
--- a/hadrian/src/Oracles/TestSettings.hs
+++ b/hadrian/src/Oracles/TestSettings.hs
@@ -28,7 +28,6 @@ data TestSetting = TestHostOS
                  | TestGhcWithInterpreter
                  | TestGhcUnregisterised
                  | TestGhcWithSMP
-                 | TestGhcDynamicByDefault
                  | TestGhcDynamic
                  | TestGhcProfiled
                  | TestAR
@@ -57,7 +56,6 @@ testSetting key = do
         TestGhcWithInterpreter    -> "GhcWithInterpreter"
         TestGhcUnregisterised     -> "GhcUnregisterised"
         TestGhcWithSMP            -> "GhcWithSMP"
-        TestGhcDynamicByDefault   -> "GhcDynamicByDefault"
         TestGhcDynamic            -> "GhcDynamic"
         TestGhcProfiled           -> "GhcProfiled"
         TestAR                    -> "AR"
diff --git a/hadrian/src/Settings/Builders/DeriveConstants.hs b/hadrian/src/Settings/Builders/DeriveConstants.hs
index be115fb789..856e85aac0 100644
--- a/hadrian/src/Settings/Builders/DeriveConstants.hs
+++ b/hadrian/src/Settings/Builders/DeriveConstants.hs
@@ -11,7 +11,6 @@ deriveConstantsPairs =
   , ("platformConstants", "--gen-haskell-value")
   ]
 
--- TODO: do we need to support `includes_CC_OPTS += -DDYNAMIC_BY_DEFAULT`?
 deriveConstantsBuilderArgs :: Args
 deriveConstantsBuilderArgs = builder DeriveConstants ? do
     cFlags <- includeCcArgs
diff --git a/hadrian/src/Settings/Builders/RunTest.hs b/hadrian/src/Settings/Builders/RunTest.hs
index 8fcc0aaee2..7ea8d4f364 100644
--- a/hadrian/src/Settings/Builders/RunTest.hs
+++ b/hadrian/src/Settings/Builders/RunTest.hs
@@ -63,7 +63,6 @@ runTestBuilderArgs = builder RunTest ? do
     let hasRtsWay w = elem w rtsWays
         hasLibWay w = elem w libWays
     hasDynamic          <- getBooleanSetting TestGhcDynamic
-    hasDynamicByDefault <- getBooleanSetting TestGhcDynamicByDefault
     withNativeCodeGen   <- getBooleanSetting TestGhcWithNativeCodeGen
     withInterpreter     <- getBooleanSetting TestGhcWithInterpreter
     unregisterised      <- getBooleanSetting TestGhcUnregisterised
@@ -127,7 +126,6 @@ runTestBuilderArgs = builder RunTest ? do
             , arg "-e", arg $ asBool "config.have_fast_bignum=" (bignumBackend /= "native" && not bignumCheck)
             , arg "-e", arg $ asBool "ghc_with_smp=" withSMP
 
-            , arg "-e", arg $ "config.ghc_dynamic_by_default=" ++ show hasDynamicByDefault
             , arg "-e", arg $ "config.ghc_dynamic=" ++ show hasDynamic
 
             , arg "-e", arg $ "config.wordsize=" ++ show wordsize
diff --git a/includes/ghc.mk b/includes/ghc.mk
index 98c154bfb6..7a863bdb19 100644
--- a/includes/ghc.mk
+++ b/includes/ghc.mk
@@ -62,10 +62,6 @@ ifneq "$(GhcWithSMP)" "YES"
 includes_CC_OPTS += -DNOSMP
 endif
 
-ifeq "$(DYNAMIC_BY_DEFAULT)" "YES"
-includes_CC_OPTS += -DDYNAMIC_BY_DEFAULT
-endif
-
 define includesHeaderVersion
 # $1 = stage
 $$(includes_$1_H_VERSION) : mk/project.mk | $$$$(dir $$$$@)/.
diff --git a/mk/config.mk.in b/mk/config.mk.in
index 9e6c3d8c40..086a9147f2 100644
--- a/mk/config.mk.in
+++ b/mk/config.mk.in
@@ -124,26 +124,6 @@ endif
 PlatformSupportsSharedLibs = $(if $(filter $(TARGETPLATFORM),\
     $(NoSharedLibsPlatformList)),NO,YES)
 
-# DYNAMIC_BY_DEFAULT says whether this compiler will default to
-# building dynamic executables, i.e. -dynamic is on.  We do this for
-# most platforms because it lets us use the system dynamic linker
-# instead of our own linker for GHCi.
-#
-# Currently this isn't possible on Windows, and we have not yet enabled
-# it on i386 while we consider the performance implications.
-#
-ifeq "$(TargetOS_CPP)" "mingw32"
-DYNAMIC_BY_DEFAULT = NO
-else ifeq "$(TargetArch_CPP)" "i386"
-DYNAMIC_BY_DEFAULT = NO
-else
-DYNAMIC_BY_DEFAULT = YES
-endif
-
-# For now, we unconditionally disable dynamic-by-default, as the
-# cabal-install's that are in the wild don't handle it properly.
-DYNAMIC_BY_DEFAULT = NO
-
 # If building both v and dyn ways, then use -dynamic-too to build them.
 # This makes the build faster.
 DYNAMIC_TOO = YES
diff --git a/mk/flavours/bench-cross-ncg.mk b/mk/flavours/bench-cross-ncg.mk
index 727f9301ae..d52eb1ca80 100644
--- a/mk/flavours/bench-cross-ncg.mk
+++ b/mk/flavours/bench-cross-ncg.mk
@@ -12,5 +12,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/mk/flavours/bench-cross.mk b/mk/flavours/bench-cross.mk
index fa332fe9f6..98f0531bc7 100644
--- a/mk/flavours/bench-cross.mk
+++ b/mk/flavours/bench-cross.mk
@@ -12,5 +12,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/mk/flavours/perf-cross-ncg.mk b/mk/flavours/perf-cross-ncg.mk
index fefff049d3..61db9b5d43 100644
--- a/mk/flavours/perf-cross-ncg.mk
+++ b/mk/flavours/perf-cross-ncg.mk
@@ -11,5 +11,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/mk/flavours/perf-cross.mk b/mk/flavours/perf-cross.mk
index 36d33b68b5..7b85cc6979 100644
--- a/mk/flavours/perf-cross.mk
+++ b/mk/flavours/perf-cross.mk
@@ -11,5 +11,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/mk/flavours/quick-cross-ncg.mk b/mk/flavours/quick-cross-ncg.mk
index 55e62f6b0f..748720f01c 100644
--- a/mk/flavours/quick-cross-ncg.mk
+++ b/mk/flavours/quick-cross-ncg.mk
@@ -12,5 +12,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/mk/flavours/quick-cross.mk b/mk/flavours/quick-cross.mk
index 07ed5f06ff..4e3f47fd67 100644
--- a/mk/flavours/quick-cross.mk
+++ b/mk/flavours/quick-cross.mk
@@ -12,5 +12,4 @@ WITH_TERMINFO      = NO
 
 BIGNUM_BACKEND       = native
 Stage1Only           = YES
-DYNAMIC_BY_DEFAULT   = NO
 DYNAMIC_GHC_PROGRAMS = NO
diff --git a/testsuite/config/ghc b/testsuite/config/ghc
index fa2c9d7c7c..4ecdc5bcb0 100644
--- a/testsuite/config/ghc
+++ b/testsuite/config/ghc
@@ -55,11 +55,8 @@ if ghc_with_threaded_rts:
 if ghc_with_dynamic_rts:
     config.have_shared_libs = True
 
-if config.ghc_dynamic_by_default and config.have_vanilla == 1:
-    config.run_ways.append('static')
-else:
-    if ghc_with_dynamic_rts:
-        config.run_ways.append('dyn')
+if ghc_with_dynamic_rts:
+    config.run_ways.append('dyn')
 
 if (config.have_profiling and ghc_with_threaded_rts):
     config.run_ways.append('profthreaded')
diff --git a/testsuite/mk/ghc-config.hs b/testsuite/mk/ghc-config.hs
index cfd6147cd0..8870a35f80 100644
--- a/testsuite/mk/ghc-config.hs
+++ b/testsuite/mk/ghc-config.hs
@@ -24,7 +24,6 @@ main = do
   getGhcFieldOrFail fields "GhcWithSMP" "Support SMP"
   getGhcFieldOrFail fields "GhcRTSWays" "RTS ways"
   getGhcFieldOrFail fields "GhcLeadingUnderscore" "Leading underscore"
-  getGhcFieldOrDefault fields "GhcDynamicByDefault" "Dynamic by default" "NO"
   getGhcFieldOrDefault fields "GhcDynamic" "GHC Dynamic" "NO"
   getGhcFieldOrDefault fields "GhcProfiled" "GHC Profiled" "NO"
   getGhcFieldProgWithDefault fields "AR" "ar command" "ar"
diff --git a/testsuite/mk/test.mk b/testsuite/mk/test.mk
index a7276207f5..bf0785116d 100644
--- a/testsuite/mk/test.mk
+++ b/testsuite/mk/test.mk
@@ -172,13 +172,7 @@ else
 RUNTEST_OPTS += -e config.have_fast_bignum=True
 endif
 
-ifeq "$(GhcDynamicByDefault)" "YES"
-RUNTEST_OPTS += -e config.ghc_dynamic_by_default=True
-CABAL_MINIMAL_BUILD = --enable-shared --disable-library-vanilla
-else
-RUNTEST_OPTS += -e config.ghc_dynamic_by_default=False
 CABAL_MINIMAL_BUILD = --enable-library-vanilla --disable-shared
-endif
 
 ifeq "$(GhcDynamic)" "YES"
 RUNTEST_OPTS += -e config.ghc_dynamic=True
diff --git a/testsuite/tests/rename/prog006/Makefile b/testsuite/tests/rename/prog006/Makefile
index f7a5f75afe..d2fedd9755 100644
--- a/testsuite/tests/rename/prog006/Makefile
+++ b/testsuite/tests/rename/prog006/Makefile
@@ -18,17 +18,13 @@ include $(TOP)/mk/test.mk
 LOCAL_PKGCONF=local.package.conf
 LOCAL_GHC_PKG = '$(GHC_PKG)' --no-user-package-db -f $(LOCAL_PKGCONF)
 
-ifeq "$(GhcDynamicByDefault)" "YES"
-RM_PROG006_EXTRA_FLAGS = -hisuf dyn_hi -osuf dyn_o
-endif
-
 rn.prog006:
 	rm -f A.hi     A.o     B/C.hi     B/C.o     Main.hi     Main.o
 	rm -f A.dyn_hi A.dyn_o B/C.dyn_hi B/C.dyn_o Main.dyn_hi Main.dyn_o
 	rm -f pkg.conf
 	rm -f pwd pwd.exe pwd.exe.manifest pwd.hi pwd.o
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make pwd -v0
-	'$(TEST_HC)' $(TEST_HC_OPTS) --make -this-unit-id test-1.0-XXX B.C -fforce-recomp -v0 $(RM_PROG006_EXTRA_FLAGS)
+	'$(TEST_HC)' $(TEST_HC_OPTS) --make -this-unit-id test-1.0-XXX B.C -fforce-recomp -v0
 	rm -f pkg.conf
 	echo "name: test" >>pkg.conf
 	echo "version: 1.0" >>pkg.conf
diff --git a/testsuite/tests/safeHaskell/check/pkg01/Makefile b/testsuite/tests/safeHaskell/check/pkg01/Makefile
index ed5185d7e5..283a7df530 100644
--- a/testsuite/tests/safeHaskell/check/pkg01/Makefile
+++ b/testsuite/tests/safeHaskell/check/pkg01/Makefile
@@ -8,11 +8,7 @@ cleanPackageDatabase.%:
 HERE := $(abspath .)
 $(eval $(call canonicalise,HERE))
 
-ifeq "$(GhcDynamicByDefault)" "YES"
-HI_SUF = dyn_hi
-else
 HI_SUF = hi
-endif
 
 mkPackageDatabase.%:
 	$(MAKE) -s --no-print-directory cleanPackageDatabase.$*
diff --git a/utils/deriveConstants/Main.hs b/utils/deriveConstants/Main.hs
index c384a7058f..3288c87800 100644
--- a/utils/deriveConstants/Main.hs
+++ b/utils/deriveConstants/Main.hs
@@ -159,8 +159,8 @@ constantWord w name expr = [(w, GetWord name (Fst (CExpr expr)))]
 constantNatural :: Where -> Name -> String -> Wanteds
 constantNatural w name expr = [(w, GetNatural name (Fst (CExpr expr)))]
 
-constantBool :: Where -> Name -> String -> Wanteds
-constantBool w name expr = [(w, GetBool name (Fst (CPPExpr expr)))]
+-- constantBool :: Where -> Name -> String -> Wanteds
+-- constantBool w name expr = [(w, GetBool name (Fst (CPPExpr expr)))]
 
 fieldOffset :: Where -> String -> String -> Wanteds
 fieldOffset w theType theField = fieldOffset_ w nameBase theType theField
@@ -661,8 +661,6 @@ wanteds os = concat
           -- Amount of pointer bits used for semi-tagging constructor closures
           ,constantWord Haskell "TAG_BITS" "TAG_BITS"
 
-          ,constantBool Haskell "DYNAMIC_BY_DEFAULT" "defined(DYNAMIC_BY_DEFAULT)"
-
           ,constantWord    Haskell "LDV_SHIFT"         "LDV_SHIFT"
           ,constantNatural Haskell "ILDV_CREATE_MASK"  "LDV_CREATE_MASK"
           ,constantNatural Haskell "ILDV_STATE_CREATE" "LDV_STATE_CREATE"