Add an IAmDead case to postInlineUnconditionally, and comments

[ghc-hetmet.git] / compiler / simplCore / SimplUtils.lhs

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 9e1be6d..693644f 100644 (file)
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -748,6 +748,11 @@ postInlineUnconditionally env top_lvl bndr occ_info rhs unfolding
                        -- int_cxt to prevent us inlining inside a lambda without some 
                        -- good reason.  See the notes on int_cxt in preInlineUnconditionally
 
+      IAmDead -> True  -- This happens; for example, the case_bndr during case of
+                       -- known constructor:  case (a,b) of x { (p,q) -> ... }
+                       -- Here x isn't mentioned in the RHS, so we don't want to
+                       -- create the (dead) let-binding  let x = (a,b) in ...
+
       other -> False
 
 -- Here's an example that we don't handle well: