From ca3f9ad296a57c4b7c6cbd6495a6b7cbc1c65fe2 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Wed, 6 Sep 2000 12:21:15 +0000
Subject: [PATCH] [project @ 2000-09-06 12:21:15 by simonmar] When compiling
 code for a case where the scrutinee is a primitve
 comparison operator, we used to place the tag in a variable
 whose unique was always the same: `mkPseudoUnique1 1'. 
 This was mostly harmless but confused the Stix inliner in
 the NCG into generating slightly less efficient code when
 the variable was used twice in a basic block.

This patch fixes the problem by generating a new unique by just
changing the "tag" of an existing unique, namely the case binder.
---
 ghc/compiler/basicTypes/Unique.lhs |    5 +++++
 ghc/compiler/codeGen/CgCase.lhs    |   13 +++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/ghc/compiler/basicTypes/Unique.lhs b/ghc/compiler/basicTypes/Unique.lhs
index 5c76485..7d9c039 100644
--- a/ghc/compiler/basicTypes/Unique.lhs
+++ b/ghc/compiler/basicTypes/Unique.lhs
@@ -27,6 +27,7 @@ module Unique (
 
 	incrUnique,			-- Used for renumbering
 	deriveUnique,			-- Ditto
+	newTagUnique,			-- Used in CgCase
 	initTyVarUnique,
 	initTidyUniques,
 
@@ -237,6 +238,7 @@ getKey		:: Unique -> Int#		-- for Var
 
 incrUnique	:: Unique -> Unique
 deriveUnique	:: Unique -> Int -> Unique
+newTagUnique	:: Unique -> Char -> Unique
 
 isTupleKey	:: Unique -> Bool
 \end{code}
@@ -254,6 +256,9 @@ incrUnique (MkUnique i) = MkUnique (i +# 1#)
 -- any of the uniques produced any other way
 deriveUnique (MkUnique i) delta = mkUnique 'X' (I# i + delta)
 
+-- newTagUnique changes the "domain" of a unique to a different char
+newTagUnique u c = mkUnique c i where (_,i) = unpkUnique u
+
 -- pop the Char in the top 8 bits of the Unique(Supply)
 
 -- No 64-bit bugs here, as long as we have at least 32 bits. --JSM
diff --git a/ghc/compiler/codeGen/CgCase.lhs b/ghc/compiler/codeGen/CgCase.lhs
index d2fb33a..481ef02 100644
--- a/ghc/compiler/codeGen/CgCase.lhs
+++ b/ghc/compiler/codeGen/CgCase.lhs
@@ -1,7 +1,7 @@
 %
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
-% $Id: CgCase.lhs,v 1.45 2000/08/02 14:13:27 rrt Exp $
+% $Id: CgCase.lhs,v 1.46 2000/09/06 12:21:15 simonmar Exp $
 %
 %********************************************************
 %*							*
@@ -61,7 +61,7 @@ import TyCon		( TyCon, isEnumerationTyCon, isUnboxedTupleTyCon,
 			)
 import Type		( Type, typePrimRep, splitAlgTyConApp, 
 			  splitTyConApp_maybe, repType )
-import Unique           ( Unique, Uniquable(..), mkPseudoUnique1 )
+import Unique           ( Unique, Uniquable(..), newTagUnique )
 import Maybes		( maybeToBool )
 import Util
 import Outputable
@@ -143,9 +143,10 @@ alternatives (in which case we lookup the tag in the relevant closure
 table to get the closure).
 
 Being a bit short of uniques for temporary variables here, we use
-mkPseudoUnique1 to generate a temporary for the tag.  We can't use
-mkBuiltinUnique, because that occasionally clashes with some
-temporaries generated for _ccall_GC, amongst others (see CgExpr.lhs).
+newTagUnique to generate a new unique from the case binder.  The case
+binder's unique will presumably have the 'c' tag (generated by
+CoreToStg), so we just change its tag to 'C' (for 'case') to ensure it
+doesn't clash with anything else.
 
 \begin{code}
 cgCase (StgPrimApp op args res_ty)
@@ -155,7 +156,7 @@ cgCase (StgPrimApp op args res_ty)
 
     let tag_amode = case op of 
 			TagToEnumOp -> only arg_amodes
-			_ -> CTemp (mkPseudoUnique1{-see above-} 1) IntRep
+			_ -> CTemp (newTagUnique (getUnique bndr) 'C') IntRep
 
 	closure = CVal (CIndex (CLbl (mkClosureTblLabel tycon) PtrRep) tag_amode PtrRep) PtrRep
     in
-- 
1.7.10.4