diff options
Diffstat (limited to 'compiler/nativeGen/X86/CodeGen.hs')
| -rw-r--r-- | compiler/nativeGen/X86/CodeGen.hs | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/compiler/nativeGen/X86/CodeGen.hs b/compiler/nativeGen/X86/CodeGen.hs index e659488fe0..e90667de42 100644 --- a/compiler/nativeGen/X86/CodeGen.hs +++ b/compiler/nativeGen/X86/CodeGen.hs @@ -1568,6 +1568,39 @@ genCCall -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +-- Do NOT unroll memcpy calls if the compiler has -mcpu=ivybridge - +-- this can be done even better using 'enhanced rep movsb', which +-- is nearly as fast as an AVX-based memcpy. +-- +-- Note: this is implied with *both* -mcpu and -march. Why? -mcpu +-- traditionally controls tuning schedules etc for the particular +-- platform. -march controls *code generation* for that platform, +-- including what instructions can be emitted. +-- +-- In this case, the *instruction* does not change, it is still +-- backwards compatible. But the actual *performance* impact and +-- schedule of the code will change, hence why we check mcpu as well. +genCCall dflags is32Bit (PrimTarget MO_Memcpy) _ + [dst, src, + (CmmLit (CmmInt n _)), + (CmmLit (CmmInt _ _))] + | supportsERMSB dflags && not is32Bit = do + code_dst <- getAnyReg dst + dst_r <- getNewRegNat II64 + code_src <- getAnyReg src + src_r <- getNewRegNat II64 + return $ code_dst dst_r `appOL` code_src src_r `appOL` + unitOL (MOV II64 (OpReg src_r) (OpReg rsi)) `appOL` + unitOL (MOV II64 (OpReg dst_r) (OpReg rdi)) `appOL` + unitOL (MOV II64 (OpImm (ImmInteger n)) (OpReg rcx)) `appOL` + unitOL REPMOVSB `appOL` nilOL + + where + supportsERMSB dflags + | Intel x <- march dflags = any (== ERMSB) (intelCPUFeatures x) + | Intel x <- mcpu dflags = any (== ERMSB) (intelCPUFeatures x) + | otherwise = False + -- Unroll memcpy calls if the source and destination pointers are at -- least DWORD aligned and the number of bytes to copy isn't too -- large. Otherwise, call C's memcpy. |