diff options
| author | Sylvain Henry <sylvain@haskus.fr> | 2016-12-09 10:26:34 -0500 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2016-12-09 10:27:34 -0500 |
| commit | d3b546b1a6058f26d5659c7f2000a7b25b7ea2ba (patch) | |
| tree | 96929e66f77af1c5f9ce451c032a24e988de57b3 /compiler/main/DynFlags.hs | |
| parent | 61932cd3eb0d5d22cb35d118fb9f87298881cd77 (diff) | |
| download | haskell-d3b546b1a6058f26d5659c7f2000a7b25b7ea2ba.tar.gz | |
Scrutinee Constant Folding
This patch introduces new rules to perform constant folding through
case-expressions.
E.g.,
```
case t -# 10# of _ { ===> case t of _ {
5# -> e1 15# -> e1
8# -> e2 18# -> e2
DEFAULT -> e DEFAULT -> e
```
The initial motivation is that it allows "Merge Nested Cases"
optimization to kick in and to further simplify the code
(see Trac #12877).
Currently we recognize the following operations for Word# and Int#: Add,
Sub, Xor, Not and Negate (for Int# only).
Test Plan: validate
Reviewers: simonpj, austin, bgamari
Reviewed By: simonpj, bgamari
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D2762
GHC Trac Issues: #12877
Diffstat (limited to 'compiler/main/DynFlags.hs')
| -rw-r--r-- | compiler/main/DynFlags.hs | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs index cbf247c49d..d7cde29557 100644 --- a/compiler/main/DynFlags.hs +++ b/compiler/main/DynFlags.hs @@ -445,6 +445,7 @@ data GeneralFlag | Opt_IgnoreAsserts | Opt_DoEtaReduction | Opt_CaseMerge + | Opt_CaseFolding -- Constant folding through case-expressions | Opt_UnboxStrictFields | Opt_UnboxSmallStrictFields | Opt_DictsCheap @@ -3561,6 +3562,7 @@ fFlagsDeps = [ flagSpec "building-cabal-package" Opt_BuildingCabalPackage, flagSpec "call-arity" Opt_CallArity, flagSpec "case-merge" Opt_CaseMerge, + flagSpec "case-folding" Opt_CaseFolding, flagSpec "cmm-elim-common-blocks" Opt_CmmElimCommonBlocks, flagSpec "cmm-sink" Opt_CmmSink, flagSpec "cse" Opt_CSE, @@ -4012,6 +4014,7 @@ optLevelFlags -- see Note [Documenting optimisation flags] , ([1,2], Opt_CallArity) , ([1,2], Opt_CaseMerge) + , ([1,2], Opt_CaseFolding) , ([1,2], Opt_CmmElimCommonBlocks) , ([1,2], Opt_CmmSink) , ([1,2], Opt_CSE) |