Wei
2008-Nov-20 12:46 UTC
[LLVMdev] Does current LLVM target-independent code generator supports my strange chip?
Because each channel contains 24-bit, so.. what is the llvm::SimpleValueType I should use for each channel? the current llvm::SimpleValueType contains i1, i8, i16, i32, i64, f32, f64, f80, none of them are fit one channel (24-bit). I think I can use i32 or f32 to represent each 24-bit channel, if the runtime result of some machine instructions exceeds 23-bit (1 bit is for sign), then it is an overflow. Is it correct to claim that the programmers needs to revise his program to fix this problem? Am I right or wrong about this thought? If there is a chip, whose registers are 24-bit long, and you have to compile C/C++ programs on it. How would you represent the following statement? int a = 3; (Programmers think sizeof(int) = 4) Wei. On Nov 19, 2:01 am, Evan Cheng <evan.ch... at apple.com> wrote:> Why not model each channel as a separate physical register? > > Evan > > On Nov 17, 2008, at 6:36 AM, Wei wrote: > > > I have a very strange and complicate H/W platform. > > It has many registers in one format. > > The register format is: > > > ------------------------------ > > ---------------------------------------------------------------------------------------- > > | 24-bit | 24-bit > > | 24-bit | 24-bit | > > ---------------------------------------------------------------------------------------------------------------------- > > a > > b > > c d > > > There are 4 channels in a register, and each channel contains 24- > > bit, hence, there are total 96-bit in 'one' register. > > You can store a 24-bit integer or a s7.16 floating-point data into > > each channel. > > You can name each channel 'a', 'b', 'c', 'd'. > > > Here is an example of the operation in this H/W platform: > > > ADD R3.ab, R1.abab, R2.bbaa > > > it means > > > Add 'abab' channel of R1 and 'bbaa' channel of R2, and > > put the result into the 'ab' channel of R3. > > > It's complicate. > > Imagine a non-existed temp register named 'Rt1', the content of its > > 'a','b','c','d' channel are got from 'a','b','a','b' channel of R1, > > and imagine another non-existed temp register named 'Rt2', the > > content of its 'a','b','c','d' channel are got from 'b','b','a','a' > > channel of R2. > > and then add Rt1 & Rt2, put the result to R3 > > this means > > the 'a' channel of R3 will be equal to the 'a' channel of Rt1 plus > > the 'a' channel of Rt2, (i.e. 'a' from R1 + 'b' from R2, because > > R1.'a'bab and R2.'b'baa) > > the 'b' channel of R3 will be equal to the 'b' channel of Rt1 plus > > the 'b' channel of Rt2, (i.e. 'b' from R1 + 'b' from R2, because > > R1.a'b'ab and R2.b'b'aa) > > the 'c' channel of R3 will be untouched, the value of the 'c' > > channel of Rt1 plus the 'c' channel of Rt2 (i.e. 'a' from R1 + 'a' > > from R2, because R1.ab'a'b and R2.bb'a'a) will be lost. > > the 'd' channel of R3 will be untouched, too. The value of the 'd' > > channel of Rt1 plus the 'd' channel of Rt2 (i.e. 'b' from R1 + 'a' > > from R2, because R1.aba'b' and R2.bba'a') will be lost, too. > > > I don't know whether I can set the 'type' of such register using a > > llvm::MVT::SimpleValueType? > > According the LLVM doc & LLVM source codes, I think llvm::MVT::v8i8, > > v2f32, etc is used to represent register for SIMD instructions. > > I don't think the operations in my platform are SIMD instructions. > > However, I can not find any llvm::MVT::SimpleValueType which can > > represents a 96-bit register. > > > Thus, my question is: > > > 1) Does current LLVM backend supports this H/W? > > 2) If yes, how can I write the type of the register class in my .td > > file? > > > (Which value should I fill in the following 'XXX' ?) > > def TempRegs : RegisterClass<"MFLEXG", [XXX], 32, [R0, R1, R2, R3, > > R4, R5, R6, R7, R8, R9, > > R10, R11, R12, > > R13, R14, R15, R16, R17, R18, R19, > > R20, R21, R22, > > R23, R24, R25, R26, R27, R28, R29, > > R30, R31]> { > > } > > > 3) If not, does this means I have to write the whole LLVM backend > > based on the basic llvm::TargetMachine & llvm::TargetData, just like > > what CBackend does? > > > -------------------------------------------------------- > > Wei Hu > >http://www.csie.ntu.edu.tw/~r88052/ > >http://wei-hu-tw.blogspot.com/ > > > _______________________________________________ > > LLVM Developers mailing list > > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu > >http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > > > _______________________________________________ > LLVM Developers mailing list > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
Daniel M Gessel
2008-Nov-20 14:24 UTC
[LLVMdev] Does current LLVM target-independent code generator supports my strange chip?
This is similar to ATI's R300/R420 pixel shaders. I'm familiar with this hardware, but not really an LLVM expert (working on a code generator myself, but learning as I go). Do you have 24-bit integer operations, or just floating point? What about load/store? Are you looking to run large C programs with complex data structures, or just comparatively simple math functions (i.e. a compute "kernel")? If you only want to support programs that can live entirely within registers, you can custom handle the conversion of the integer/float constants that LLVM spits out and i32/f32 sounds a good place to start - LLVM's mem2reg and inlining is very effective at getting rid the majority of stack operations, and I'd assume you'd have intrinsics for I/O. If you want to support memory operations, your integers need to support the addressing range correctly - you effectively have 17 bits of mantissa - so it may be a tight squeeze without 24 bit integer ops (shifts and ands and stuff will also be a painful, but that's a more expansive topic). Dan On Nov 20, 2008, at 7:46 AM, Wei wrote:> Because each channel contains 24-bit, so.. what is the > llvm::SimpleValueType I should use for each channel? > the current llvm::SimpleValueType contains i1, i8, i16, i32, i64, f32, > f64, f80, none of them are fit one channel (24-bit). > > I think I can use i32 or f32 to represent each 24-bit channel, if the > runtime result of some machine instructions exceeds 23-bit (1 bit is > for sign), then it is an overflow. > Is it correct to claim that the programmers needs to revise his > program to fix this problem? > Am I right or wrong about this thought? > > If there is a chip, whose registers are 24-bit long, and you have to > compile C/C++ programs on it. > How would you represent the following statement? > > int a = 3; > (Programmers think sizeof(int) = 4) > > Wei. > > On Nov 19, 2:01 am, Evan Cheng <evan.ch... at apple.com> wrote: >> Why not model each channel as a separate physical register? >> >> Evan >> >> On Nov 17, 2008, at 6:36 AM, Wei wrote: >> >>> I have a very strange and complicate H/W platform. >>> It has many registers in one format. >>> The register format is: >> >>> ------------------------------ >>> ---------------------------------------------------------------------------------------- >>> | 24-bit | 24-bit >>> | 24-bit | 24-bit | >>> ---------------------------------------------------------------------------------------------------------------------- >>> a >>> b >>> c d >> >>> There are 4 channels in a register, and each channel contains 24- >>> bit, hence, there are total 96-bit in 'one' register. >>> You can store a 24-bit integer or a s7.16 floating-point data into >>> each channel. >>> You can name each channel 'a', 'b', 'c', 'd'. >> >>> Here is an example of the operation in this H/W platform: >> >>> ADD R3.ab, R1.abab, R2.bbaa >> >>> it means >> >>> Add 'abab' channel of R1 and 'bbaa' channel of R2, and >>> put the result into the 'ab' channel of R3. >> >>> It's complicate. >>> Imagine a non-existed temp register named 'Rt1', the content of its >>> 'a','b','c','d' channel are got from 'a','b','a','b' channel of R1, >>> and imagine another non-existed temp register named 'Rt2', the >>> content of its 'a','b','c','d' channel are got from 'b','b','a','a' >>> channel of R2. >>> and then add Rt1 & Rt2, put the result to R3 >>> this means >>> the 'a' channel of R3 will be equal to the 'a' channel of Rt1 plus >>> the 'a' channel of Rt2, (i.e. 'a' from R1 + 'b' from R2, because >>> R1.'a'bab and R2.'b'baa) >>> the 'b' channel of R3 will be equal to the 'b' channel of Rt1 plus >>> the 'b' channel of Rt2, (i.e. 'b' from R1 + 'b' from R2, because >>> R1.a'b'ab and R2.b'b'aa) >>> the 'c' channel of R3 will be untouched, the value of the 'c' >>> channel of Rt1 plus the 'c' channel of Rt2 (i.e. 'a' from R1 + 'a' >>> from R2, because R1.ab'a'b and R2.bb'a'a) will be lost. >>> the 'd' channel of R3 will be untouched, too. The value of the 'd' >>> channel of Rt1 plus the 'd' channel of Rt2 (i.e. 'b' from R1 + 'a' >>> from R2, because R1.aba'b' and R2.bba'a') will be lost, too. >> >>> I don't know whether I can set the 'type' of such register using a >>> llvm::MVT::SimpleValueType? >>> According the LLVM doc & LLVM source codes, I think llvm::MVT::v8i8, >>> v2f32, etc is used to represent register for SIMD instructions. >>> I don't think the operations in my platform are SIMD instructions. >>> However, I can not find any llvm::MVT::SimpleValueType which can >>> represents a 96-bit register. >> >>> Thus, my question is: >> >>> 1) Does current LLVM backend supports this H/W? >>> 2) If yes, how can I write the type of the register class in my .td >>> file? >> >>> (Which value should I fill in the following 'XXX' ?) >>> def TempRegs : RegisterClass<"MFLEXG", [XXX], 32, [R0, R1, R2, R3, >>> R4, R5, R6, R7, R8, R9, >>> R10, R11, R12, >>> R13, R14, R15, R16, R17, R18, R19, >>> R20, R21, R22, >>> R23, R24, R25, R26, R27, R28, R29, >>> R30, R31]> { >>> } >> >>> 3) If not, does this means I have to write the whole LLVM backend >>> based on the basic llvm::TargetMachine & llvm::TargetData, just like >>> what CBackend does? >> >>> -------------------------------------------------------- >>> Wei Hu >>> http://www.csie.ntu.edu.tw/~r88052/ >>> http://wei-hu-tw.blogspot.com/ >> >>> _______________________________________________ >>> LLVM Developers mailing list >>> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu >>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev >> >> >> >> _______________________________________________ >> LLVM Developers mailing list >> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
Evan Cheng
2008-Nov-21 07:54 UTC
[LLVMdev] Does current LLVM target-independent code generator supports my strange chip?
24 bit is not unusual in the DSP world. I suppose int == 24 bit integer for some of these chips? There isn't a i24 simple type. However, you can create an extended integer type. See getExtendedIntegerVT. It's almost guaranteed you will have to change a chunk of target independent codegen to support the use of an extended type though. Evan On Nov 20, 2008, at 4:46 AM, Wei wrote:> Because each channel contains 24-bit, so.. what is the > llvm::SimpleValueType I should use for each channel? > the current llvm::SimpleValueType contains i1, i8, i16, i32, i64, f32, > f64, f80, none of them are fit one channel (24-bit). > > I think I can use i32 or f32 to represent each 24-bit channel, if the > runtime result of some machine instructions exceeds 23-bit (1 bit is > for sign), then it is an overflow. > Is it correct to claim that the programmers needs to revise his > program to fix this problem? > Am I right or wrong about this thought? > > If there is a chip, whose registers are 24-bit long, and you have to > compile C/C++ programs on it. > How would you represent the following statement? > > int a = 3; > (Programmers think sizeof(int) = 4) > > Wei. > > On Nov 19, 2:01 am, Evan Cheng <evan.ch... at apple.com> wrote: >> Why not model each channel as a separate physical register? >> >> Evan >> >> On Nov 17, 2008, at 6:36 AM, Wei wrote: >> >>> I have a very strange and complicate H/W platform. >>> It has many registers in one format. >>> The register format is: >> >>> ------------------------------ >>> ---------------------------------------------------------------------------------------- >>> | 24-bit | 24-bit >>> | 24-bit | 24-bit | >>> ---------------------------------------------------------------------------------------------------------------------- >>> a >>> b >>> c d >> >>> There are 4 channels in a register, and each channel contains 24- >>> bit, hence, there are total 96-bit in 'one' register. >>> You can store a 24-bit integer or a s7.16 floating-point data into >>> each channel. >>> You can name each channel 'a', 'b', 'c', 'd'. >> >>> Here is an example of the operation in this H/W platform: >> >>> ADD R3.ab, R1.abab, R2.bbaa >> >>> it means >> >>> Add 'abab' channel of R1 and 'bbaa' channel of R2, and >>> put the result into the 'ab' channel of R3. >> >>> It's complicate. >>> Imagine a non-existed temp register named 'Rt1', the content of its >>> 'a','b','c','d' channel are got from 'a','b','a','b' channel of R1, >>> and imagine another non-existed temp register named 'Rt2', the >>> content of its 'a','b','c','d' channel are got from 'b','b','a','a' >>> channel of R2. >>> and then add Rt1 & Rt2, put the result to R3 >>> this means >>> the 'a' channel of R3 will be equal to the 'a' channel of Rt1 plus >>> the 'a' channel of Rt2, (i.e. 'a' from R1 + 'b' from R2, because >>> R1.'a'bab and R2.'b'baa) >>> the 'b' channel of R3 will be equal to the 'b' channel of Rt1 plus >>> the 'b' channel of Rt2, (i.e. 'b' from R1 + 'b' from R2, because >>> R1.a'b'ab and R2.b'b'aa) >>> the 'c' channel of R3 will be untouched, the value of the 'c' >>> channel of Rt1 plus the 'c' channel of Rt2 (i.e. 'a' from R1 + 'a' >>> from R2, because R1.ab'a'b and R2.bb'a'a) will be lost. >>> the 'd' channel of R3 will be untouched, too. The value of the 'd' >>> channel of Rt1 plus the 'd' channel of Rt2 (i.e. 'b' from R1 + 'a' >>> from R2, because R1.aba'b' and R2.bba'a') will be lost, too. >> >>> I don't know whether I can set the 'type' of such register using a >>> llvm::MVT::SimpleValueType? >>> According the LLVM doc & LLVM source codes, I think llvm::MVT::v8i8, >>> v2f32, etc is used to represent register for SIMD instructions. >>> I don't think the operations in my platform are SIMD instructions. >>> However, I can not find any llvm::MVT::SimpleValueType which can >>> represents a 96-bit register. >> >>> Thus, my question is: >> >>> 1) Does current LLVM backend supports this H/W? >>> 2) If yes, how can I write the type of the register class in my .td >>> file? >> >>> (Which value should I fill in the following 'XXX' ?) >>> def TempRegs : RegisterClass<"MFLEXG", [XXX], 32, [R0, R1, R2, R3, >>> R4, R5, R6, R7, R8, R9, >>> R10, R11, R12, >>> R13, R14, R15, R16, R17, R18, R19, >>> R20, R21, R22, >>> R23, R24, R25, R26, R27, R28, R29, >>> R30, R31]> { >>> } >> >>> 3) If not, does this means I have to write the whole LLVM backend >>> based on the basic llvm::TargetMachine & llvm::TargetData, just like >>> what CBackend does? >> >>> -------------------------------------------------------- >>> Wei Hu >>> http://www.csie.ntu.edu.tw/~r88052/ >>> http://wei-hu-tw.blogspot.com/ >> >>> _______________________________________________ >>> LLVM Developers mailing list >>> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu >>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev >> >> >> >> _______________________________________________ >> LLVM Developers mailing list >> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp:// >> lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
Wei
2008-Nov-22 15:48 UTC
[LLVMdev] Does current LLVM target-independent code generator supports my strange chip?
Do you mean MVT::getIntegerVT? Because I can not find getExtendedIntegerVT in the llvm source codes. I am excited seeing this function, however I have the following more questions. 1) You mention I will have to change not small amount of target indenpendent codegen codes to support this extended type. Are there any document to describe how to do such kind modification? I see there is a "extending LLVM" document in the official website, and I don't know whether the info written in its "Adding a new SelectionDAG node" section (although its quite simple) is what I need? If not, where can I get more information about this topic? 2) What will go wrong if I use MVT::i32 or MVT::f32 to represent such a 24-bit register? Will LLVM optimization pass produce wrong codes or other really bad things? Or just produce codes which will overflow in some should not overflow situation. I think I am pretty new in LLVM world. wanna to get more help from you expert. Thx. Wei. On Nov 21, 3:54 pm, Evan Cheng <ech... at apple.com> wrote:> 24 bit is not unusual in the DSP world. I suppose int == 24 bit > integer for some of these chips? > > There isn't a i24 simple type. However, you can create an extended > integer type. See getExtendedIntegerVT. It's almost guaranteed you > will have to change a chunk of target independent codegen to support > the use of an extended type though. > > Evan > > On Nov 20, 2008, at 4:46 AM, Wei wrote: > > > > > Because each channel contains 24-bit, so.. what is the > > llvm::SimpleValueType I should use for each channel? > > the current llvm::SimpleValueType contains i1, i8, i16, i32, i64, f32, > > f64, f80, none of them are fit one channel (24-bit). > > > I think I can use i32 or f32 to represent each 24-bit channel, if the > > runtime result of some machine instructions exceeds 23-bit (1 bit is > > for sign), then it is an overflow. > > Is it correct to claim that the programmers needs to revise his > > program to fix this problem? > > Am I right or wrong about this thought? > > > If there is a chip, whose registers are 24-bit long, and you have to > > compile C/C++ programs on it. > > How would you represent the following statement? > > > int a = 3; > > (Programmers think sizeof(int) = 4) > > > Wei. > > > On Nov 19, 2:01 am, Evan Cheng <evan.ch... at apple.com> wrote: > >> Why not model each channel as a separate physical register? > > >> Evan > > >> On Nov 17, 2008, at 6:36 AM, Wei wrote: > > >>> I have a very strange and complicate H/W platform. > >>> It has many registers in one format. > >>> The register format is: > > >>> ------------------------------ > >>> ---------------------------------------------------------------------------------------- > >>> | 24-bit | 24-bit > >>> | 24-bit | 24-bit | > >>> ---------------------------------------------------------------------------------------------------------------------- > >>> a > >>> b > >>> c d > > >>> There are 4 channels in a register, and each channel contains 24- > >>> bit, hence, there are total 96-bit in 'one' register. > >>> You can store a 24-bit integer or a s7.16 floating-point data into > >>> each channel. > >>> You can name each channel 'a', 'b', 'c', 'd'. > > >>> Here is an example of the operation in this H/W platform: > > >>> ADD R3.ab, R1.abab, R2.bbaa > > >>> it means > > >>> Add 'abab' channel of R1 and 'bbaa' channel of R2, and > >>> put the result into the 'ab' channel of R3. > > >>> It's complicate. > >>> Imagine a non-existed temp register named 'Rt1', the content of its > >>> 'a','b','c','d' channel are got from 'a','b','a','b' channel of R1, > >>> and imagine another non-existed temp register named 'Rt2', the > >>> content of its 'a','b','c','d' channel are got from 'b','b','a','a' > >>> channel of R2. > >>> and then add Rt1 & Rt2, put the result to R3 > >>> this means > >>> the 'a' channel of R3 will be equal to the 'a' channel of Rt1 plus > >>> the 'a' channel of Rt2, (i.e. 'a' from R1 + 'b' from R2, because > >>> R1.'a'bab and R2.'b'baa) > >>> the 'b' channel of R3 will be equal to the 'b' channel of Rt1 plus > >>> the 'b' channel of Rt2, (i.e. 'b' from R1 + 'b' from R2, because > >>> R1.a'b'ab and R2.b'b'aa) > >>> the 'c' channel of R3 will be untouched, the value of the 'c' > >>> channel of Rt1 plus the 'c' channel of Rt2 (i.e. 'a' from R1 + 'a' > >>> from R2, because R1.ab'a'b and R2.bb'a'a) will be lost. > >>> the 'd' channel of R3 will be untouched, too. The value of the 'd' > >>> channel of Rt1 plus the 'd' channel of Rt2 (i.e. 'b' from R1 + 'a' > >>> from R2, because R1.aba'b' and R2.bba'a') will be lost, too. > > >>> I don't know whether I can set the 'type' of such register using a > >>> llvm::MVT::SimpleValueType? > >>> According the LLVM doc & LLVM source codes, I think llvm::MVT::v8i8, > >>> v2f32, etc is used to represent register for SIMD instructions. > >>> I don't think the operations in my platform are SIMD instructions. > >>> However, I can not find any llvm::MVT::SimpleValueType which can > >>> represents a 96-bit register. > > >>> Thus, my question is: > > >>> 1) Does current LLVM backend supports this H/W? > >>> 2) If yes, how can I write the type of the register class in my .td > >>> file? > > >>> (Which value should I fill in the following 'XXX' ?) > >>> def TempRegs : RegisterClass<"MFLEXG", [XXX], 32, [R0, R1, R2, R3, > >>> R4, R5, R6, R7, R8, R9, > >>> R10, R11, R12, > >>> R13, R14, R15, R16, R17, R18, R19, > >>> R20, R21, R22, > >>> R23, R24, R25, R26, R27, R28, R29, > >>> R30, R31]> { > >>> } > > >>> 3) If not, does this means I have to write the whole LLVM backend > >>> based on the basic llvm::TargetMachine & llvm::TargetData, just like > >>> what CBackend does? > > >>> -------------------------------------------------------- > >>> Wei Hu > >>>http://www.csie.ntu.edu.tw/~r88052/ > >>>http://wei-hu-tw.blogspot.com/ > > >>> _______________________________________________ > >>> LLVM Developers mailing list > >>> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu > >>>http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > >> _______________________________________________ > >> LLVM Developers mailing list > >> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp:// > >> lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > > _______________________________________________ > > LLVM Developers mailing list > > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu > >http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > _______________________________________________ > LLVM Developers mailing list > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
Wei
2008-Nov-22 16:03 UTC
[LLVMdev] Does current LLVM target-independent code generator supports my strange chip?
I have 24-bit integer operations as well as 24-bit floating point (s7.16) operations. The H/W supports load/store instructions, however, they does suggest us not to use these load/store instructions besides debugging purpose. That is to say, you can imagine we don't have load/store instructions, we don't have memory, we just have registers. I will run OpenGL shading laugnage programs on these chip. About your comments, I (a new LLVM user) have some more questions: 1) You mention "custom handle the conversion of the integer/float constants that LLVM spits out", does it means: I have to register a callback function which will operate when LLVM wants to spits out a constant value to memory. But what about non- constant value? ex: int a; and LLVM wants to put a into memory. and I don't really know what the "i32/f32 sounds a good place to start" means... 2) I don't know why you mention "I'd assume you'd have intrinsics for I/O." 3) I don't think I get you about the following statements:> If you want to support memory operations, your integers need to > support the addressing range correctly - you effectively have 17 bits > of mantissa - so it may be a tight squeeze without 24 bit integer ops > (shifts and ands and stuff will also be a painful, but that's a more > expansive topic).Can you give some example? Really really thanks about your comments. Wei. On Nov 20, 10:24 pm, Daniel M Gessel <ges... at apple.com> wrote:> This is similar to ATI's R300/R420 pixel shaders. I'm familiar with > this hardware, but not really an LLVM expert (working on a code > generator myself, but learning as I go). > > Do you have 24-bit integer operations, or just floating point? > > What about load/store? > > Are you looking to run large C programs with complex data structures, > or just comparatively simple math functions (i.e. a compute "kernel")? > > If you only want to support programs that can live entirely within > registers, you can custom handle the conversion of the integer/float > constants that LLVM spits out and i32/f32 sounds a good place to start > - LLVM's mem2reg and inlining is very effective at getting rid the > majority of stack operations, and I'd assume you'd have intrinsics for > I/O. > > If you want to support memory operations, your integers need to > support the addressing range correctly - you effectively have 17 bits > of mantissa - so it may be a tight squeeze without 24 bit integer ops > (shifts and ands and stuff will also be a painful, but that's a more > expansive topic). > > Dan > > On Nov 20, 2008, at 7:46 AM, Wei wrote: > > > > > Because each channel contains 24-bit, so.. what is the > > llvm::SimpleValueType I should use for each channel? > > the current llvm::SimpleValueType contains i1, i8, i16, i32, i64, f32, > > f64, f80, none of them are fit one channel (24-bit). > > > I think I can use i32 or f32 to represent each 24-bit channel, if the > > runtime result of some machine instructions exceeds 23-bit (1 bit is > > for sign), then it is an overflow. > > Is it correct to claim that the programmers needs to revise his > > program to fix this problem? > > Am I right or wrong about this thought? > > > If there is a chip, whose registers are 24-bit long, and you have to > > compile C/C++ programs on it. > > How would you represent the following statement? > > > int a = 3; > > (Programmers think sizeof(int) = 4) > > > Wei. > > > On Nov 19, 2:01 am, Evan Cheng <evan.ch... at apple.com> wrote: > >> Why not model each channel as a separate physical register? > > >> Evan > > >> On Nov 17, 2008, at 6:36 AM, Wei wrote: > > >>> I have a very strange and complicate H/W platform. > >>> It has many registers in one format. > >>> The register format is: > > >>> ------------------------------ > >>> ---------------------------------------------------------------------------------------- > >>> | 24-bit | 24-bit > >>> | 24-bit | 24-bit | > >>> ---------------------------------------------------------------------------------------------------------------------- > >>> a > >>> b > >>> c d > > >>> There are 4 channels in a register, and each channel contains 24- > >>> bit, hence, there are total 96-bit in 'one' register. > >>> You can store a 24-bit integer or a s7.16 floating-point data into > >>> each channel. > >>> You can name each channel 'a', 'b', 'c', 'd'. > > >>> Here is an example of the operation in this H/W platform: > > >>> ADD R3.ab, R1.abab, R2.bbaa > > >>> it means > > >>> Add 'abab' channel of R1 and 'bbaa' channel of R2, and > >>> put the result into the 'ab' channel of R3. > > >>> It's complicate. > >>> Imagine a non-existed temp register named 'Rt1', the content of its > >>> 'a','b','c','d' channel are got from 'a','b','a','b' channel of R1, > >>> and imagine another non-existed temp register named 'Rt2', the > >>> content of its 'a','b','c','d' channel are got from 'b','b','a','a' > >>> channel of R2. > >>> and then add Rt1 & Rt2, put the result to R3 > >>> this means > >>> the 'a' channel of R3 will be equal to the 'a' channel of Rt1 plus > >>> the 'a' channel of Rt2, (i.e. 'a' from R1 + 'b' from R2, because > >>> R1.'a'bab and R2.'b'baa) > >>> the 'b' channel of R3 will be equal to the 'b' channel of Rt1 plus > >>> the 'b' channel of Rt2, (i.e. 'b' from R1 + 'b' from R2, because > >>> R1.a'b'ab and R2.b'b'aa) > >>> the 'c' channel of R3 will be untouched, the value of the 'c' > >>> channel of Rt1 plus the 'c' channel of Rt2 (i.e. 'a' from R1 + 'a' > >>> from R2, because R1.ab'a'b and R2.bb'a'a) will be lost. > >>> the 'd' channel of R3 will be untouched, too. The value of the 'd' > >>> channel of Rt1 plus the 'd' channel of Rt2 (i.e. 'b' from R1 + 'a' > >>> from R2, because R1.aba'b' and R2.bba'a') will be lost, too. > > >>> I don't know whether I can set the 'type' of such register using a > >>> llvm::MVT::SimpleValueType? > >>> According the LLVM doc & LLVM source codes, I think llvm::MVT::v8i8, > >>> v2f32, etc is used to represent register for SIMD instructions. > >>> I don't think the operations in my platform are SIMD instructions. > >>> However, I can not find any llvm::MVT::SimpleValueType which can > >>> represents a 96-bit register. > > >>> Thus, my question is: > > >>> 1) Does current LLVM backend supports this H/W? > >>> 2) If yes, how can I write the type of the register class in my .td > >>> file? > > >>> (Which value should I fill in the following 'XXX' ?) > >>> def TempRegs : RegisterClass<"MFLEXG", [XXX], 32, [R0, R1, R2, R3, > >>> R4, R5, R6, R7, R8, R9, > >>> R10, R11, R12, > >>> R13, R14, R15, R16, R17, R18, R19, > >>> R20, R21, R22, > >>> R23, R24, R25, R26, R27, R28, R29, > >>> R30, R31]> { > >>> } > > >>> 3) If not, does this means I have to write the whole LLVM backend > >>> based on the basic llvm::TargetMachine & llvm::TargetData, just like > >>> what CBackend does? > > >>> -------------------------------------------------------- > >>> Wei Hu > >>>http://www.csie.ntu.edu.tw/~r88052/ > >>>http://wei-hu-tw.blogspot.com/ > > >>> _______________________________________________ > >>> LLVM Developers mailing list > >>> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu > >>>http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > >> _______________________________________________ > >> LLVM Developers mailing list > >> LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > > _______________________________________________ > > LLVM Developers mailing list > > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.edu > >http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > _______________________________________________ > LLVM Developers mailing list > LLVM... at cs.uiuc.edu http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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