Extract hard-coded LLVM opt flags into a file

To resolve ticket #11295, I think it makes sense to stop hard-coding
the pass sequences used by GHC when compiling with LLVM into the
compiler
itself.

This patchset introduces a companion to the existing `llvm-targets` file
called `llvm-passes`. The passes file is a simple association list that
holds the default LLVM `opt` pass sequence used by GHC. This allows end
users to easily save their favorite optimization flags when compiling
with LLVM.

The main benefit for ticket #11295 is that when adding a custom pass
sequence, it tends to be an extremely long string that would be
unsightly in the code.

This is essentially part 1 of 2 for ticket #11295.

Test Plan: ./validate

Reviewers: bgamari, angerman

Reviewed By: angerman

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4695

1 files changed, 16 insertions, 10 deletions

diff --git a/compiler/main/SysTools.hs b/compiler/main/SysTools.hs
index 619e0b65e7..2e52ef97da 100644
--- a/compiler/main/SysTools.hs
+++ b/compiler/main/SysTools.hs
@@ -13,7 +13,7 @@
 module SysTools (
         -- * Initialisation
         initSysTools,
-        initLlvmTargets,
+        initLlvmConfig,
 
         -- * Interface to system tools
         module SysTools.Tasks,
@@ -110,16 +110,22 @@ stuff.
 ************************************************************************
 -}
 
-initLlvmTargets :: Maybe String
-                -> IO LlvmTargets
-initLlvmTargets mbMinusB
-  = do top_dir <- findTopDir mbMinusB
-       let llvmTargetsFile = top_dir </> "llvm-targets"
-       llvmTargetsStr <- readFile llvmTargetsFile
-       case maybeReadFuzzy llvmTargetsStr of
-         Just s -> return (fmap mkLlvmTarget <$> s)
-         Nothing -> pgmError ("Can't parse " ++ show llvmTargetsFile)
+initLlvmConfig :: Maybe String
+                -> IO LlvmConfig
+initLlvmConfig mbMinusB
+  = do
+      targets <- readAndParse "llvm-targets" mkLlvmTarget
+      passes <- readAndParse "llvm-passes" id
+      return (targets, passes)
   where
+    readAndParse name builder =
+      do top_dir <- findTopDir mbMinusB
+         let llvmConfigFile = top_dir </> name
+         llvmConfigStr <- readFile llvmConfigFile
+         case maybeReadFuzzy llvmConfigStr of
+           Just s -> return (fmap builder <$> s)
+           Nothing -> pgmError ("Can't parse " ++ show llvmConfigFile)
+
     mkLlvmTarget :: (String, String, String) -> LlvmTarget
     mkLlvmTarget (dl, cpu, attrs) = LlvmTarget dl cpu (words attrs)