[commit: ghc] simd: Fixup stack spills when generating AVX instructions. (c5cc24c)

[Geoffrey Mainland]

Repository : http://darcs.haskell.org/ghc.git/

On branch  : simd

https://github.com/ghc/ghc/commit/c5cc24cebeb85b4bc3fd9ba78e27ba2603ba1f6e

>---------------------------------------------------------------

commit c5cc24cebeb85b4bc3fd9ba78e27ba2603ba1f6e
Author: Geoffrey Mainland <gmainlan at microsoft.com>
Date:   Sat Nov 26 12:45:23 2011 +0000

    Fixup stack spills when generating AVX instructions.
    
    LLVM uses aligned AVX moves to spill values onto the stack, which requires
    32-bye aligned stacks. Since the stack in only 16-byte aligned, LLVM inserts
    extra instructions that munge the stack pointer. This is very very bad for the
    GHC calling convention, so we tell LLVM to assume the stack is 32-byte
    aligned. This patch rewrites the spill instructions that LLVM generates so they
    do not require an aligned stack.

>---------------------------------------------------------------

 compiler/llvmGen/LlvmMangler.hs | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/compiler/llvmGen/LlvmMangler.hs b/compiler/llvmGen/LlvmMangler.hs
index 83a2be7..745dcc6 100644
--- a/compiler/llvmGen/LlvmMangler.hs
+++ b/compiler/llvmGen/LlvmMangler.hs
@@ -20,6 +20,10 @@ import System.IO
 import Data.List ( sortBy )
 import Data.Function ( on )
 
+#if x86_64_TARGET_ARCH
+#define REWRITE_AVX
+#endif
+
 -- Magic Strings
 secStmt, infoSec, newLine, textStmt, dataStmt, syntaxUnified :: B.ByteString
 secStmt       = B.pack "\t.section\t"
@@ -47,6 +51,7 @@ llvmFixupAsm dflags f1 f2 = {-# SCC "llvm_mangler" #-} do
     w <- openBinaryFile f2 WriteMode
     ss <- readSections r w
     hClose r
+    let fixed = (map rewriteAVX . fixTables) ss
     let fixed = fixTables ss
     mapM_ (writeSection w) fixed
     hClose w
@@ -90,6 +95,39 @@ writeSection w (hdr, cts) = do
     B.hPutStrLn w hdr
   B.hPutStrLn w cts
 
+#if REWRITE_AVX
+rewriteAVX :: Section -> Section
+rewriteAVX = rewriteVmovaps . rewriteVmovdqa
+
+rewriteVmovdqa :: Section -> Section
+rewriteVmovdqa = rewriteInstructions vmovdqa vmovdqu
+  where
+    vmovdqa, vmovdqu :: B.ByteString
+    vmovdqa = B.pack "vmovdqa"
+    vmovdqu = B.pack "vmovdqu"
+
+rewriteVmovap :: Section -> Section
+rewriteVmovap = rewriteInstructions vmovap vmovup
+  where
+    vmovap, vmovup :: B.ByteString
+    vmovap = B.pack "vmovap"
+    vmovup = B.pack "vmovup"
+
+rewriteInstructions :: B.ByteString -> B.ByteString -> Section -> Section
+rewriteInstructions matchBS replaceBS (hdr, cts) =
+    (hdr, loop cts)
+  where
+    loop :: B.ByteString -> B.ByteString
+    loop cts =
+        case B.breakSubstring cts matchBS of
+          (hd,tl) | B.null tl -> hd
+                  | otherwise -> hd `B.append` replaceBS `B.append`
+                                 loop (B.drop (B.length matchBS) tl)
+#else /* !REWRITE_AVX */
+rewriteAVX :: Section -> Section
+rewriteAVX = id
+#endif /* !REWRITE_SSE */
+
 -- | Reorder and convert sections so info tables end up next to the
 -- code. Also does stack fixups.
 fixTables :: [Section] -> [Section]