Add support for byte endian swapping for Word 16/32/64.

  * Exposes bSwap{,16,32,64}# primops
  * Add a new machop: MO_BSwap
  * Use a Stg implementation (hs_bswap{16,32,64}) for other implementation
    in NCG.
  * Generate bswap in X86 NCG for 32 and 64 bits, and for 16 bits, bswap+shr
    instead of using xchg.
  * Generate llvm.bswap intrinsics in llvm codegen.

Authored-by: Vincent Hanquez <tab@snarc.org>
Signed-off-by: Austin Seipp <aseipp@pobox.com>

11 files changed, 97 insertions, 26 deletions

diff --git a/compiler/cmm/CmmMachOp.hs b/compiler/cmm/CmmMachOp.hs
index fae84e5d53..8d42bbd2cb 100644
--- a/compiler/cmm/CmmMachOp.hs
+++ b/compiler/cmm/CmmMachOp.hs
@@ -529,6 +529,7 @@ data CallishMachOp
   | MO_Memmove
 
   | MO_PopCnt Width
+  | MO_BSwap Width
   deriving (Eq, Show)
 
 pprCallishMachOp :: CallishMachOp -> SDoc
diff --git a/compiler/cmm/PprC.hs b/compiler/cmm/PprC.hs
index 00ba7acb06..b0c9bd3f2f 100644
--- a/compiler/cmm/PprC.hs
+++ b/compiler/cmm/PprC.hs
@@ -738,6 +738,7 @@ pprCallishMachOp_for_C mop
         MO_Memcpy       -> ptext (sLit "memcpy")
         MO_Memset       -> ptext (sLit "memset")
         MO_Memmove      -> ptext (sLit "memmove")
+        (MO_BSwap w)    -> ptext (sLit $ bSwapLabel w)
         (MO_PopCnt w)   -> ptext (sLit $ popCntLabel w)
         (MO_UF_Conv w)  -> ptext (sLit $ word2FloatLabel w)
 
diff --git a/compiler/codeGen/StgCmmPrim.hs b/compiler/codeGen/StgCmmPrim.hs
index 54002e8171..7ce329a707 100644
--- a/compiler/codeGen/StgCmmPrim.hs
+++ b/compiler/codeGen/StgCmmPrim.hs
@@ -541,6 +541,11 @@ emitPrimOp _      [] CopyMutableByteArrayOp [src,src_off,dst,dst_off,n] =
 emitPrimOp _      [] SetByteArrayOp [ba,off,len,c] =
     doSetByteArrayOp ba off len c
 
+emitPrimOp _      [res] BSwap16Op [w] = emitBSwapCall res w W16
+emitPrimOp _      [res] BSwap32Op [w] = emitBSwapCall res w W32
+emitPrimOp _      [res] BSwap64Op [w] = emitBSwapCall res w W64
+emitPrimOp dflags [res] BSwapOp   [w] = emitBSwapCall res w (wordWidth dflags)
+
 -- Population count
 emitPrimOp _      [res] PopCnt8Op  [w] = emitPopCntCall res w W8
 emitPrimOp _      [res] PopCnt16Op [w] = emitPopCntCall res w W16
@@ -1568,6 +1573,13 @@ emitAllocateCall res cap n = do
     allocate = CmmLit (CmmLabel (mkForeignLabel (fsLit "allocate") Nothing
                                  ForeignLabelInExternalPackage IsFunction))
 
+emitBSwapCall :: LocalReg -> CmmExpr -> Width -> FCode ()
+emitBSwapCall res x width = do
+    emitPrimCall
+        [ res ]
+        (MO_BSwap width)
+        [ x ]
+
 emitPopCntCall :: LocalReg -> CmmExpr -> Width -> FCode ()
 emitPopCntCall res x width = do
     emitPrimCall
diff --git a/compiler/llvmGen/LlvmCodeGen/CodeGen.hs b/compiler/llvmGen/LlvmCodeGen/CodeGen.hs
index d223a5c9cd..6f898fa56c 100644
--- a/compiler/llvmGen/LlvmCodeGen/CodeGen.hs
+++ b/compiler/llvmGen/LlvmCodeGen/CodeGen.hs
@@ -221,30 +221,11 @@ genCall t@(PrimTarget MO_Prefetch_Data) [] args = do
                 `appOL` trash `snocOL` call
     return (stmts, top1 ++ top2)
 
--- Handle popcnt function specifically since GHC only really has i32 and i64
--- types and things like Word8 are backed by an i32 and just present a logical
--- i8 range. So we must handle conversions from i32 to i8 explicitly as LLVM
--- is strict about types.
-genCall t@(PrimTarget op@(MO_PopCnt w)) [dst] args = do
-    let width = widthToLlvmInt w
-        dstTy = cmmToLlvmType $ localRegType dst
-
-    fname                       <- cmmPrimOpFunctions op
-    (fptr, _, top3)             <- getInstrinct fname width [width]
-
-    dstV                        <- getCmmReg (CmmLocal dst)
-
-    let (_, arg_hints) = foreignTargetHints t
-    let args_hints = zip args arg_hints
-    (argsV, stmts2, top2)       <- arg_vars args_hints ([], nilOL, [])
-    (argsV', stmts4)            <- castVars $ zip argsV [width]
-    (retV, s1)                  <- doExpr width $ Call StdCall fptr argsV' []
-    ([retV'], stmts5)           <- castVars [(retV,dstTy)]
-    let s2                       = Store retV' dstV
-
-    let stmts = stmts2 `appOL` stmts4 `snocOL`
-                s1 `appOL` stmts5 `snocOL` s2
-    return (stmts, top2 ++ top3)
+-- Handle PopCnt and BSwap that need to only convert arg and return types
+genCall t@(PrimTarget (MO_PopCnt w)) dsts args =
+    genCallSimpleCast w t dsts args
+genCall t@(PrimTarget (MO_BSwap w)) dsts args =
+    genCallSimpleCast w t dsts args
 
 -- Handle memcpy function specifically since llvm's intrinsic version takes
 -- some extra parameters.
@@ -390,9 +371,36 @@ genCall target res args = do
                     return (allStmts `snocOL` s2 `snocOL` s3
                                 `appOL` retStmt, top1 ++ top2)
 
+-- Handle simple function call that only need simple type casting, of the form:
+--   truncate arg >>= \a -> call(a) >>= zext
+--
+-- since GHC only really has i32 and i64 types and things like Word8 are backed
+-- by an i32 and just present a logical i8 range. So we must handle conversions
+-- from i32 to i8 explicitly as LLVM is strict about types.
+genCallSimpleCast :: Width -> ForeignTarget -> [CmmFormal] -> [CmmActual]
+              -> LlvmM StmtData
+genCallSimpleCast w t@(PrimTarget op) [dst] args = do
+    let width = widthToLlvmInt w
+        dstTy = cmmToLlvmType $ localRegType dst
+
+    fname                       <- cmmPrimOpFunctions op
+    (fptr, _, top3)             <- getInstrinct fname width [width]
+
+    dstV                        <- getCmmReg (CmmLocal dst)
 
--- genCallSimpleCast _ _ _ dsts _ =
---    panic ("genCallSimpleCast: " ++ show (length dsts) ++ " dsts")
+    let (_, arg_hints) = foreignTargetHints t
+    let args_hints = zip args arg_hints
+    (argsV, stmts2, top2)       <- arg_vars args_hints ([], nilOL, [])
+    (argsV', stmts4)            <- castVars $ zip argsV [width]
+    (retV, s1)                  <- doExpr width $ Call StdCall fptr argsV' []
+    ([retV'], stmts5)           <- castVars [(retV,dstTy)]
+    let s2                       = Store retV' dstV
+
+    let stmts = stmts2 `appOL` stmts4 `snocOL`
+                s1 `appOL` stmts5 `snocOL` s2
+    return (stmts, top2 ++ top3)
+genCallSimpleCast _ _ dsts _ =
+    panic ("genCallSimpleCast: " ++ show (length dsts) ++ " dsts")
 
 -- | Create a function pointer from a target.
 getFunPtr :: (LMString -> LlvmType) -> ForeignTarget
@@ -534,6 +542,7 @@ cmmPrimOpFunctions mop = do
     MO_Memset     -> fsLit $ "llvm.memset."  ++ intrinTy2
 
     (MO_PopCnt w) -> fsLit $ "llvm.ctpop."  ++ showSDoc dflags (ppr $ widthToLlvmInt w)
+    (MO_BSwap w)  -> fsLit $ "llvm.bswap."  ++ showSDoc dflags (ppr $ widthToLlvmInt w)
 
     MO_Prefetch_Data -> fsLit "llvm.prefetch"
 
diff --git a/compiler/nativeGen/CPrim.hs b/compiler/nativeGen/CPrim.hs
index dd9d38f434..a6f4cab7bd 100644
--- a/compiler/nativeGen/CPrim.hs
+++ b/compiler/nativeGen/CPrim.hs
@@ -1,6 +1,7 @@
 -- | Generating C symbol names emitted by the compiler.
 module CPrim
     ( popCntLabel
+    , bSwapLabel
     , word2FloatLabel
     ) where
 
@@ -16,6 +17,14 @@ popCntLabel w = "hs_popcnt" ++ pprWidth w
     pprWidth W64 = "64"
     pprWidth w   = pprPanic "popCntLabel: Unsupported word width " (ppr w)
 
+bSwapLabel :: Width -> String
+bSwapLabel w = "hs_bswap" ++ pprWidth w
+  where
+    pprWidth W16 = "16"
+    pprWidth W32 = "32"
+    pprWidth W64 = "64"
+    pprWidth w   = pprPanic "bSwapLabel: Unsupported word width " (ppr w)
+
 word2FloatLabel :: Width -> String
 word2FloatLabel w = "hs_word2float" ++ pprWidth w
   where
diff --git a/compiler/nativeGen/PPC/CodeGen.hs b/compiler/nativeGen/PPC/CodeGen.hs
index 39b64002dc..65533d8f9a 100644
--- a/compiler/nativeGen/PPC/CodeGen.hs
+++ b/compiler/nativeGen/PPC/CodeGen.hs
@@ -1155,6 +1155,7 @@ genCCall' dflags gcp target dest_regs args0
                     MO_Memset    -> (fsLit "memset", False)
                     MO_Memmove   -> (fsLit "memmove", False)
 
+                    MO_BSwap w   -> (fsLit $ bSwapLabel w, False)
                     MO_PopCnt w  -> (fsLit $ popCntLabel w, False)
 
                     MO_S_QuotRem {}  -> unsupported
diff --git a/compiler/nativeGen/SPARC/CodeGen.hs b/compiler/nativeGen/SPARC/CodeGen.hs
index 9c84a38f6a..5d2b9a9d6d 100644
--- a/compiler/nativeGen/SPARC/CodeGen.hs
+++ b/compiler/nativeGen/SPARC/CodeGen.hs
@@ -647,6 +647,7 @@ outOfLineMachOp_table mop
         MO_Memset    -> fsLit "memset"
         MO_Memmove   -> fsLit "memmove"
 
+        MO_BSwap w   -> fsLit $ bSwapLabel w
         MO_PopCnt w  -> fsLit $ popCntLabel w
 
         MO_S_QuotRem {}  -> unsupported
diff --git a/compiler/nativeGen/X86/CodeGen.hs b/compiler/nativeGen/X86/CodeGen.hs
index 848a804cf1..f6143d3fb9 100644
--- a/compiler/nativeGen/X86/CodeGen.hs
+++ b/compiler/nativeGen/X86/CodeGen.hs
@@ -1658,6 +1658,29 @@ genCCall _ (PrimTarget MO_Touch) _ _ = return nilOL
 
 genCCall _ (PrimTarget MO_Prefetch_Data) _ _ = return nilOL
 
+genCCall is32Bit (PrimTarget (MO_BSwap width)) [dst] [src] = do
+    dflags <- getDynFlags
+    let platform = targetPlatform dflags
+    let dst_r = getRegisterReg platform False (CmmLocal dst)
+    case width of
+        W64 | is32Bit -> do
+               ChildCode64 vcode rlo <- iselExpr64 src
+               let dst_rhi = getHiVRegFromLo dst_r
+                   rhi     = getHiVRegFromLo rlo
+               return $ vcode `appOL`
+                        toOL [ MOV II32 (OpReg rlo) (OpReg dst_rhi),
+                               MOV II32 (OpReg rhi) (OpReg dst_r),
+                               BSWAP II32 dst_rhi,
+                               BSWAP II32 dst_r ]
+        W16 -> do code_src <- getAnyReg src
+                  return $ code_src dst_r `appOL`
+                           unitOL (BSWAP II32 dst_r) `appOL`
+                           unitOL (SHR II32 (OpImm $ ImmInt 16) (OpReg dst_r))
+        _   -> do code_src <- getAnyReg src
+                  return $ code_src dst_r `appOL` unitOL (BSWAP size dst_r)
+  where
+    size = intSize width
+
 genCCall is32Bit (PrimTarget (MO_PopCnt width)) dest_regs@[dst]
          args@[src] = do
     sse4_2 <- sse4_2Enabled
@@ -2325,6 +2348,7 @@ outOfLineCmmOp mop res args
               MO_Memmove   -> fsLit "memmove"
 
               MO_PopCnt _  -> fsLit "popcnt"
+              MO_BSwap _   -> fsLit "bswap"
 
               MO_UF_Conv _ -> unsupported
 
diff --git a/compiler/nativeGen/X86/Instr.hs b/compiler/nativeGen/X86/Instr.hs
index 76f0e8bd91..266a4ea58a 100644
--- a/compiler/nativeGen/X86/Instr.hs
+++ b/compiler/nativeGen/X86/Instr.hs
@@ -208,6 +208,7 @@ data Instr
         | XOR         Size Operand Operand
         | NOT         Size Operand
         | NEGI        Size Operand              -- NEG instruction (name clash with Cond)
+        | BSWAP       Size Reg
 
         -- Shifts (amount may be immediate or %cl only)
         | SHL         Size Operand{-amount-} Operand
@@ -351,6 +352,7 @@ x86_regUsageOfInstr platform instr
 
     XOR    _ src dst    -> usageRM src dst
     NOT    _ op         -> usageM op
+    BSWAP  _ reg        -> mkRU [reg] [reg]
     NEGI   _ op         -> usageM op
     SHL    _ imm dst    -> usageRM imm dst
     SAR    _ imm dst    -> usageRM imm dst
@@ -489,6 +491,7 @@ x86_patchRegsOfInstr instr env
     OR   sz src dst     -> patch2 (OR   sz) src dst
     XOR  sz src dst     -> patch2 (XOR  sz) src dst
     NOT  sz op          -> patch1 (NOT  sz) op
+    BSWAP sz reg        -> BSWAP sz (env reg)
     NEGI sz op          -> patch1 (NEGI sz) op
     SHL  sz imm dst     -> patch1 (SHL sz imm) dst
     SAR  sz imm dst     -> patch1 (SAR sz imm) dst
diff --git a/compiler/nativeGen/X86/Ppr.hs b/compiler/nativeGen/X86/Ppr.hs
index 75d18a1ff4..7f9c6901da 100644
--- a/compiler/nativeGen/X86/Ppr.hs
+++ b/compiler/nativeGen/X86/Ppr.hs
@@ -578,6 +578,7 @@ pprInstr (XOR size src dst) = pprSizeOpOp (sLit "xor")  size src dst
 pprInstr (POPCNT size src dst) = pprOpOp (sLit "popcnt") size src (OpReg dst)
 
 pprInstr (NOT size op) = pprSizeOp (sLit "not") size op
+pprInstr (BSWAP size op) = pprSizeOp (sLit "bswap") size (OpReg op)
 pprInstr (NEGI size op) = pprSizeOp (sLit "neg") size op
 
 pprInstr (SHL size src dst) = pprShift (sLit "shl") size src dst
diff --git a/compiler/prelude/primops.txt.pp b/compiler/prelude/primops.txt.pp
index f31a237189..3d3518b095 100644
--- a/compiler/prelude/primops.txt.pp
+++ b/compiler/prelude/primops.txt.pp
@@ -363,6 +363,15 @@ primop   PopCnt64Op   "popCnt64#"   GenPrimOp   WORD64 -> Word#
 primop   PopCntOp   "popCnt#"   Monadic   Word# -> Word#
     {Count the number of set bits in a word.}
 
+primop   BSwap16Op   "byteSwap16#"   Monadic   Word# -> Word#
+    {Swap bytes in the lower 16 bits of a word. The higher bytes are undefined. }
+primop   BSwap32Op   "byteSwap32#"   Monadic   Word# -> Word#
+    {Swap bytes in the lower 32 bits of a word. The higher bytes are undefined. }
+primop   BSwap64Op   "byteSwap64#"   Monadic   WORD64 -> WORD64
+    {Swap bytes in a 64 bits of a word.}
+primop   BSwapOp     "byteSwap#"     Monadic   Word# -> Word#
+    {Swap bytes in a word.}
+
 ------------------------------------------------------------------------
 section "Narrowings" 
 	{Explicit narrowing of native-sized ints or words.}