From: simonmar <unknown>
Date: Wed, 12 Jan 2005 16:33:54 +0000 (+0000)
Subject: [project @ 2005-01-12 16:33:54 by simonmar]
X-Git-Tag: Initial_conversion_from_CVS_complete~1251
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=a609df425d10b6d5e87cf43d01b4c2cd83551fbb;p=ghc-hetmet.git

[project @ 2005-01-12 16:33:54 by simonmar]
Fix a bug in mk_switch.
---

diff --git a/ghc/compiler/codeGen/CgUtils.hs b/ghc/compiler/codeGen/CgUtils.hs
index a8e9c39..414e90a 100644
--- a/ghc/compiler/codeGen/CgUtils.hs
+++ b/ghc/compiler/codeGen/CgUtils.hs
@@ -405,11 +405,15 @@ mk_switch tag_expr branches mb_deflt lo_tag hi_tag
 		find_branch :: ConTagZ -> Maybe BlockId
 		find_branch i = assocDefault mb_deflt tagged_blk_ids i
 
-		arms = [ find_branch (i+lo_tag) | i <- [0..n_tags-1]]
+		-- NB. we have eliminated impossible branches at
+		-- either end of the range (see below), so the first
+		-- tag of a real branch is real_lo_tag (not lo_tag).
+		arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
 
-	        switch_stmt = CmmSwitch (cmmOffset tag_expr (- lo_tag)) arms
+	        switch_stmt = CmmSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
 
-	; return (oneCgStmt switch_stmt)
+	; ASSERT(not (all isNothing arms)) 
+	  return (oneCgStmt switch_stmt)
 	}
 
   -- if we can knock off a bunch of default cases with one if, then do so