Deserialize IfaceId more lazily

This change sped up the total validate --build-only time by 0.8%
on my test system; hopefully a representative result.

I didn't bother making the other constructors lazy because for
IfaceData and IfaceClass we need to pull on some of the fields
in loadDecl, and all the others seem much more rare than IfaceId.

Test Plan: validate, perf

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D3269

1 files changed, 2 insertions, 6 deletions

diff --git a/compiler/iface/IfaceSyn.hs b/compiler/iface/IfaceSyn.hs
index d73a738786..1c30476960 100644
--- a/compiler/iface/IfaceSyn.hs
+++ b/compiler/iface/IfaceSyn.hs
@@ -1565,9 +1565,7 @@ instance Binary IfaceDecl where
     put_ bh (IfaceId name ty details idinfo) = do
         putByte bh 0
         putIfaceTopBndr bh name
-        put_ bh ty
-        put_ bh details
-        put_ bh idinfo
+        lazyPut bh (ty, details, idinfo)
 
     put_ bh (IfaceData a1 a2 a3 a4 a5 a6 a7 a8 a9) = do
         putByte bh 2
@@ -1657,9 +1655,7 @@ instance Binary IfaceDecl where
         h <- getByte bh
         case h of
             0 -> do name    <- get bh
-                    ty      <- get bh
-                    details <- get bh
-                    idinfo  <- get bh
+                    ~(ty, details, idinfo) <- lazyGet bh
                     return (IfaceId name ty details idinfo)
             1 -> error "Binary.get(TyClDecl): ForeignType"
             2 -> do a1  <- getIfaceTopBndr bh