Thanks Simon, primops worked fine, but not I'm getting assembler errors(even though -dcore-lint, -dstg-lint and -dcmm-lint are all passing). The error is caused by this STG expression: case (#,#) [ds_gX8 ds_gX9] of _ { (#,#) tag_gWR ubx_gWS -> case tag_gWR of tag_gWR { __DEFAULT -> GHC.Err.undefined; 1# -> let { sat_sWD :: [GHC.Types.Char] = \u srt:SRT:[roK :-> GHC.Show.$fShowInt] [] let { sat_sWC :: GHC.Types.Int = NO_CCS GHC.Types.I#! [ubx_gWS]; } in GHC.Show.show GHC.Show.$fShowInt sat_sWC; } in let { sat_sWB :: [GHC.Types.Char] = \u srt:SRT:[0k :-> GHC.CString.unpackCString#] [] GHC.CString.unpackCString# "Left "#; } in GHC.Base.++ sat_sWB sat_sWD; 2# -> let { co_gWT :: GHC.Prim.Float# = sat-only \s [] int2Float# [ubx_gWS]; } in let { sat_sWH :: [GHC.Types.Char] = \u srt:SRT:[rd2 :-> GHC.Float.$fShowFloat] [] let { sat_sWG :: GHC.Types.Float = NO_CCS GHC.Types.F#! [co_gWT]; } in GHC.Show.show GHC.Float.$fShowFloat sat_sWG; } in let { sat_sWF :: [GHC.Types.Char] = \u srt:SRT:[0k :-> GHC.CString.unpackCString#] [] GHC.CString.unpackCString# "Right "#; } in GHC.Base.++ sat_sWF sat_sWH; }; }; In the first case(when the tag is 1#) I'm not doing any coercions, second argument of the tuple is directly used. In the second case(when the tag is 2#), I'm generating this let-binding: let { co_gWT :: GHC.Prim.Float# = sat-only \s [] int2Float# [ubx_gWS]; } And then in the RHS of case alternative I'm using co_gWT instead of ubx_gWS, but for some reason GHC is generating invalid assembly for this expression: /tmp/ghc2889_0/ghc_2.s: Assembler messages: /tmp/ghc2889_0/ghc_2.s:125:0: error: Error: `16(%xmm1)' is not a valid base/index expression `gcc' failed in phase `Assembler'. (Exit code: 1) The assembly seems to be: ==================== Asm code ==================== .section .text .align 8 .quad 4294967296 .quad 18 co_gWT_info: _cY7: _cY9: movq 16(%xmm1),%rax cvtsi2ssq %rax,%xmm0 movss %xmm0,%xmm1 jmp *(%rbp) .size co_gWT_info, .-co_gWT_info Do you have any ideas why this may be happening? 2015-12-07 7:23 GMT-05:00 Simon Peyton Jones :

If memory serves, there are primops for converting between unboxed values of different widths.

Certainly converting between a float and a non-float will require an instruction on some architectures, since they use different register sets.

Re (2) I have no idea. You'll need to get more information... pprTrace or something.

Simon

| -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Ömer | Sinan Agacan | Sent: 06 December 2015 18:25 | To: ghc-devs | Subject: question about coercions between primitive types in STG level | | Hi all, | | In my compiler pass(D1559, see ElimUbxSums.hs) I'm doing some unsafe | coercions at the STG level. It works fine for lifted types, but for | unlifted ones I'm having some problems. What I'm trying to do is given | a number of primitive types I'm finding the one with biggest size, and | then generating a constructor that takes this biggest primitive type | as argument. | | The problem is that this is not working very well - GHC is generating | illegal instructions that try to load a F32 value to a register | allocated for I64, using movss instruction. | | CoreLint is catching this error and printing this: | | Cmm lint error: | in basic block c1hF | in assignment: | _g16W::I64 = 4.5 :: W32; // CmmAssign | Reg ty: I64 | Rhs ty: F32 | | So I have two questions about this: | | 1. Is there a way to safely do this? What are my options here? What | I'm trying | to do is to use a single data constructor field for different | primitive | types. The field is guaranteed to be as big as necessary. | | 2. In the Cmm code shown above, the type annotation is showing `W32` | but in the | error message it says `F32`. I'm confused about this, is this error | message | given because the sizes don't match? (64bits vs 32bits) Why the | type | annotation says W32 while the value has type F32? | | Thanks.. | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.h | askell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7ced6a1fbfa6254e5 | 2a7d808d2fe6a9a63%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=7j3fQs4 | ox67SZbA4jv4uPVVdvp5X5yUUuMaqp4sh%2fpg%3d

Simon's right, you need an explicit conversion, and unfortunately those conversions don't currently exist. You would have to add them to the MachOp type, and implement them in each of the native code generators. The good news is that if you did this, we could implement cheap conversions between the IEEE floating point types and their representations as unboxed integers, which is currently done by poking the values to memory and then peeking them back at the desired type. There's a ticket for this around somewhere.... Cheers Simon On 07/12/2015 12:23, Simon Peyton Jones wrote:

If memory serves, there are primops for converting between unboxed values of different widths.

Certainly converting between a float and a non-float will require an instruction on some architectures, since they use different register sets.

Re (2) I have no idea. You'll need to get more information... pprTrace or something.

Simon

| -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Ömer | Sinan Agacan | Sent: 06 December 2015 18:25 | To: ghc-devs | Subject: question about coercions between primitive types in STG level | | Hi all, | | In my compiler pass(D1559, see ElimUbxSums.hs) I'm doing some unsafe | coercions at the STG level. It works fine for lifted types, but for | unlifted ones I'm having some problems. What I'm trying to do is given | a number of primitive types I'm finding the one with biggest size, and | then generating a constructor that takes this biggest primitive type | as argument. | | The problem is that this is not working very well - GHC is generating | illegal instructions that try to load a F32 value to a register | allocated for I64, using movss instruction. | | CoreLint is catching this error and printing this: | | Cmm lint error: | in basic block c1hF | in assignment: | _g16W::I64 = 4.5 :: W32; // CmmAssign | Reg ty: I64 | Rhs ty: F32 | | So I have two questions about this: | | 1. Is there a way to safely do this? What are my options here? What | I'm trying | to do is to use a single data constructor field for different | primitive | types. The field is guaranteed to be as big as necessary. | | 2. In the Cmm code shown above, the type annotation is showing `W32` | but in the | error message it says `F32`. I'm confused about this, is this error | message | given because the sizes don't match? (64bits vs 32bits) Why the | type | annotation says W32 while the value has type F32? | | Thanks.. | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail.h | askell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7ced6a1fbfa6254e5 | 2a7d808d2fe6a9a63%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=7j3fQs4 | ox67SZbA4jv4uPVVdvp5X5yUUuMaqp4sh%2fpg%3d _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

Omer Honestly I'm out of my depth here, and so time-poor that I don't think I can realistically help much. I hope others can be more useful! Simon | -----Original Message----- | From: Ömer Sinan Ağacan [mailto:omeragacan@gmail.com] | Sent: 10 December 2015 02:46 | To: Simon Marlow ; Simon Peyton Jones | ; ghc-devs ; rwbarton@gmail.com | Subject: Re: question about coercions between primitive types in STG level | | Thanks for all the answers, | | Simon, do you remember anything about the ticket about converting between | floating point types and integers? I spend quite a bit of time in Trac | searching for this but couldn't find it. | | | Before implementing a new primop, MachOp, and code generation functions for | that I tried this: Since type signature of this new primop will be same as | float2Int# I thought maybe I should first make current implementation | working, and then I can just change the primop to coerceFloat2Int# and it | would work. | | However I'm still this same problem(illegal assembly). What I changed is I | looked at the GHC-generated, working STG code that uses float2Int#, and | tried to generate a very similar code myself. The change I had to make for | this was to use a case expression instead of let expression to bind result | of this primop. | | Here's an example. This STG is working fine: | | sat_s1Ic :: GHC.Types.Float -> | https://na01.safelinks.protection.outlook.com/?url=GHC.Types.IO&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=BnXCV6rCnP5ibif0LwHYctTd6BVA85horA1D | 1Uketrk%3d () = | \r srt:SRT:[0B :-> System.IO.print, | rUB :-> GHC.Show.$fShowInt] [ds_s1I7] | case | ds_s1I7 :: GHC.Types.Float :: Alg GHC.Types.Float | of | (wild_s1I8 :: GHC.Types.Float) | { GHC.Types.F# (f_s1I9 :: GHC.Prim.Float#) -> | case | float2Int# [(f_s1I9 :: GHC.Prim.Float#)] :: Prim | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d# | of | (sat_s1Ia :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#) | { __DEFAULT -> | let { | sat_s1Ib :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Types.Int&data=01%7c0 | 1%7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72 | f988bf86f141af91ab2d7cd011db47%7c1&sdata=SP%2fVPreBotFEHkZyK2Y1YSX30dEjkei6h | PARLyK11Yw%3d = | NO_CCS GHC.Types.I#! [(sat_s1Ia :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#)]; | } in | System.IO.print | :: forall a_aUq. GHC.Show.Show a_aUq => a_aUq -> | https://na01.safelinks.protection.outlook.com/?url=GHC.Types.IO&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=BnXCV6rCnP5ibif0LwHYctTd6BVA85horA1D | 1Uketrk%3d () | (GHC.Show.$fShowInt :: GHC.Show.Show | https://na01.safelinks.protection.outlook.com/?url=GHC.Types.Int&data=01%7c0 | 1%7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72 | f988bf86f141af91ab2d7cd011db47%7c1&sdata=SP%2fVPreBotFEHkZyK2Y1YSX30dEjkei6h | PARLyK11Yw%3d) | (sat_s1Ib :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Types.Int&data=01%7c0 | 1%7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72 | f988bf86f141af91ab2d7cd011db47%7c1&sdata=SP%2fVPreBotFEHkZyK2Y1YSX30dEjkei6h | PARLyK11Yw%3d); | }; | }; | | (Sorry for extra noisy output, I changed Outputable instances to print some | extra info) | | This code is generated by GHC for a program that uses the primop directly | and it's working. This is the code generated by my pass: | | Main.main2 :: [GHC.Types.Char] = | \u srt:SRT:[r4 :-> Main.showEither2] [] | case | case | float2Int# [1.2#] :: Prim | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d# | of | (co_g21m :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#) | { __DEFAULT -> (#,#) [2## (co_g21m :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#)]; | } :: UbxTup 2 | of | (sat_s21b :: (# | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#, | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d# #)) | { (#,#) (sat_g21R :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#) (sat_g21S :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#) -> | Main.showEither2 | :: (# | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#, | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d# #) -> [GHC.Types.Char] | (sat_g21R :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#) (sat_g21S :: | https://na01.safelinks.protection.outlook.com/?url=GHC.Prim.Int&data=01%7c01 | %7csimonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7c72f | 988bf86f141af91ab2d7cd011db47%7c1&sdata=GMVWFJOAJ4IZj2t9WZ2hX3h7xm7U7Dbn0OfU | gjON958%3d#); | }; | | Types look correct, and I'm using a case expression to bind the result of | the primop. But generated assembly for this is still invalid! I'm wondering | if there are some invariants that I'm invalidating here, even although - | dstg-lint is passing. Does anyone know what I might be doing wrong here? | | One thing that I'm not being very careful is the information about live | variables, but I don't see how it might be related with this illegal | instruction error. | | Thanks again.. | | 2015-12-07 13:57 GMT-05:00 Simon Marlow : | > Simon's right, you need an explicit conversion, and unfortunately | > those conversions don't currently exist. You would have to add them | > to the MachOp type, and implement them in each of the native code | generators. | > | > The good news is that if you did this, we could implement cheap | > conversions between the IEEE floating point types and their | > representations as unboxed integers, which is currently done by poking | > the values to memory and then peeking them back at the desired type. | > There's a ticket for this around somewhere.... | > | > Cheers | > Simon | > | > | > On 07/12/2015 12:23, Simon Peyton Jones wrote: | >> | >> If memory serves, there are primops for converting between unboxed | >> values of different widths. | >> | >> Certainly converting between a float and a non-float will require an | >> instruction on some architectures, since they use different register | sets. | >> | >> Re (2) I have no idea. You'll need to get more information... | >> pprTrace or something. | >> | >> Simon | >> | >> | -----Original Message----- | >> | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | >> | Ömer Sinan Agacan | >> | Sent: 06 December 2015 18:25 | >> | To: ghc-devs | >> | Subject: question about coercions between primitive types in STG | >> | level | >> | | >> | Hi all, | >> | | >> | In my compiler pass(D1559, see ElimUbxSums.hs) I'm doing some | >> | unsafe coercions at the STG level. It works fine for lifted types, | >> | but for unlifted ones I'm having some problems. What I'm trying to | >> | do is given a number of primitive types I'm finding the one with | >> | biggest size, and then generating a constructor that takes this | >> | biggest primitive type as argument. | >> | | >> | The problem is that this is not working very well - GHC is | >> | generating illegal instructions that try to load a F32 value to a | >> | register allocated for I64, using movss instruction. | >> | | >> | CoreLint is catching this error and printing this: | >> | | >> | Cmm lint error: | >> | in basic block c1hF | >> | in assignment: | >> | _g16W::I64 = 4.5 :: W32; // CmmAssign | >> | Reg ty: I64 | >> | Rhs ty: F32 | >> | | >> | So I have two questions about this: | >> | | >> | 1. Is there a way to safely do this? What are my options here? | >> | What I'm trying | >> | to do is to use a single data constructor field for different | >> | primitive | >> | types. The field is guaranteed to be as big as necessary. | >> | | >> | 2. In the Cmm code shown above, the type annotation is showing | >> | `W32` but in the | >> | error message it says `F32`. I'm confused about this, is this | >> | error message | >> | given because the sizes don't match? (64bits vs 32bits) Why the | >> | type | >> | annotation says W32 while the value has type F32? | >> | | >> | Thanks.. | >> | _______________________________________________ | >> | ghc-devs mailing list | >> | ghc-devs@haskell.org | >> | | >> | https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmai | >> | l.h | >> | askell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc- | >> | | >> | devs&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7ced6a1fbfa625 | >> | 4e5 | >> | | >> | 2a7d808d2fe6a9a63%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=7j3f | >> | Qs4 ox67SZbA4jv4uPVVdvp5X5yUUuMaqp4sh%2fpg%3d | >> _______________________________________________ | >> ghc-devs mailing list | >> ghc-devs@haskell.org | >> https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fmail. | >> haskell.org%2fcgi-bin%2fmailman%2flistinfo%2fghc-devs&data=01%7c01%7c | >> simonpj%40064d.mgd.microsoft.com%7c900655295d074c8b867b08d3010c2165%7 | >> c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=DYbGX1f9UBqSTEN9qDWBiqM9H | >> ucMEitgBCnh4ZZjneg%3d | >> | >

Simon Marlow writes:

I'm not sure what you did to get to this point, but let me elaborate on what I think is needed:

- Add primops for the conversions - Add appropriate MachOps for the conversions (F32 -> I32, F64 -> I64) - Make sure the primops get compiled into the appropriate MachOps (see StgCmmPrim) - Implement those MachOps in the native code generator (X86/CodeGen.hs).

For this part you'll need to figure out what the appropriate x86/x86_64 instructions to generate are; it may be that you need to go via memory, which would be unfortunate.

Ömer, LLVM can be a useful tool for working out proper instruction generation. You may find this LLVM snippet helpful (along with some simplified output), $ cat hi.ll define i32 @float_to_int(float %x) { %x1 = fadd float 1.0, %x; %y = bitcast float %x1 to i32; ret i32 %y; } define i64 @double_to_int(double %x) { %x1 = fadd double 0.1, %x; %y = bitcast double %x1 to i64; ret i64 %y; } $ llc hi.ll --march=x86 && cat hi.s float_to_int: # @float_to_int fld1 fadds 8(%esp) fstps (%esp) movl (%esp), %eax popl %edx retl double_to_int: # @double_to_int fldl 16(%esp) faddl .LCPI1_0 fstpl (%esp) movl (%esp), %eax movl 4(%esp), %edx addl $12, %esp retl $ llc hi.ll --march=x86_64 && cat hi.s float_to_int: # @float_to_int addss .LCPI0_0(%rip), %xmm0 movd %xmm0, %eax double_to_int: # @double_to_int addsd .LCPI1_0(%rip), %xmm0 movd %xmm0, %rax retq