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| author | mrchebas@gmail.com <unknown> | 2007-01-19 15:07:49 +0000 |
|---|---|---|
| committer | mrchebas@gmail.com <unknown> | 2007-01-19 15:07:49 +0000 |
| commit | a32098431939d2411798312b11f18cf99e9f724b (patch) | |
| tree | 746ea8ecbe3b9b6eef1822fca919b9ff40be2678 /compiler/codeGen | |
| parent | 95d05f883245488f22bfa9dbbfd6d55cc7303a81 (diff) | |
| download | haskell-a32098431939d2411798312b11f18cf99e9f724b.tar.gz | |
don't make jump tables for small switches (<= 4 branches)
Only affects -fasm: gcc makes its own decisions about jump tables
Diffstat (limited to 'compiler/codeGen')
| -rw-r--r-- | compiler/codeGen/CgUtils.hs | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/compiler/codeGen/CgUtils.hs b/compiler/codeGen/CgUtils.hs index ab39080c16..29b972ce62 100644 --- a/compiler/codeGen/CgUtils.hs +++ b/compiler/codeGen/CgUtils.hs @@ -480,9 +480,11 @@ mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C text "real_lo_tag: " <+> int real_lo_tag <+> text "real_hi_tag: " <+> int real_hi_tag) $ -} ASSERT( n_branches > 1 && n_tags > 1 ) - n_tags > 2 && (small || dense || via_C) - -- a 2-branch switch always turns into an if. - small = n_tags <= 4 + n_tags > 2 && (via_C || (dense && big_enough)) + -- up to 4 branches we use a decision tree, otherwise + -- a switch (== jump table in the NCG). This seems to be + -- optimal, and corresponds with what gcc does. + big_enough = n_branches > 4 dense = n_branches > (n_tags `div` 2) n_branches = length branches |