Flag for defaulting the codegen GhcStageXDefaultNewCodegen.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

compiler/ghc.mk

@@ -491,6 +491,18 @@ compiler_stage1_HC_OPTS += $(GhcStage1HcOpts)
 compiler_stage2_HC_OPTS += $(GhcStage2HcOpts)
 compiler_stage3_HC_OPTS += $(GhcStage3HcOpts)
 
+ifeq "$(GhcStage1DefaultNewCodegen)" "YES"
+compiler_stage1_HC_OPTS += -DGHC_DEFAULT_NEW_CODEGEN
+endif
+
+ifeq "$(GhcStage2DefaultNewCodegen)" "YES"
+compiler_stage2_HC_OPTS += -DGHC_DEFAULT_NEW_CODEGEN
+endif
+
+ifeq "$(GhcStage3DefaultNewCodegen)" "YES"
+compiler_stage3_HC_OPTS += -DGHC_DEFAULT_NEW_CODEGEN
+endif
+
 ifneq "$(BINDIST)" "YES"
 
 compiler_stage2_TAGS_HC_OPTS = -package ghc

compiler/main/DynFlags.hs

@@ -1646,6 +1646,10 @@ defaultFlags
 
       Opt_SharedImplib,
 
+#if GHC_DEFAULT_NEW_CODEGEN
+      Opt_TryNewCodeGen,
+#endif
+
       Opt_GenManifest,
       Opt_EmbedManifest,
       Opt_PrintBindContents,

mk/config.mk.in

@@ -97,6 +97,16 @@ GhcStage1HcOpts=
 GhcStage2HcOpts=-O2
 GhcStage3HcOpts=-O2
 
+# These options modify whether or not a built compiler for a bootstrap
+# stage defaults to using the new code generation path.  The new
+# code generation path is a bit slower, so for development just
+# GhcStage2DefaultNewCodegen=YES, but it's also a good idea to try
+# building all libraries and the stage2 compiler with the
+# new code generator, which involves GhcStage1DefaultNewCodegen=YES.
+GhcStage1DefaultNewCodegen=NO
+GhcStage2DefaultNewCodegen=NO
+GhcStage3DefaultNewCodegen=NO
+
 GhcDebugged=NO
 GhcDynamic=NO