I think I found another issue with Code generation, this time on Cortex-M4:

I need to write Byte Aligned to the Data Register of the SPI Interface of a STM32 Chip....

so what I (try) to do is:

using pByte(@DR)^ to force a single byte transfer and I succeed with the byte alignment.......

BUT

please check the generated assembler, the requirred LSRS (SHR) is not done by the compiler.

Just for fun I removed the byte alignment and the LSRS shows up...

@Jeppe, can this have to do with the fix for Cortex-M0 you provided to me a few days ago or is this just another issue?

    pByte(@DR)^ := aWord shr 8;
     0800 185A  LDR          R0, [R11, #-0x38]      0800 185E  ADD.W        R1, R0, #0xC      0800 1862  LDRH         R0, [R11, #-0x30]      0800 1866  STRB         R0, [R1]

    DR := aWord shr 8;
     0800 1868  LDRH         R0, [R11, #-0x30]      0800 186C  LSRS         R1, R0, #8      0800 186E  LDR          R0, [R11, #-0x38]      0800 1872  STR          R1, [R0, #0xC]

Thank you,

Michael

Forgot to mention I am using Trunk compiler from today revision 41187 ond optimization level was -O1

Michael

I can only reproduce this with peephole optimization turned on (O2). Can you share more code that reproduces it?

Either way here's a patch that might fix it?

Best Regards,
Jeppe

Your patch did the trick, assembler Code is looking good now:

   pByte(@DR)^ := (aWord shr 8);
     0800 187E  LDR          R0, [R11, #-0x38]      0800 1882  ADD.W        R1, R0, #0xC      0800 1886  LDRH         R0, [R11, #-0x30]      0800 188A  UXTB         R0, R0, ROR #8      0800 188E  STRB         R0, [R1]

and my application also works fine now.

This is a small demo of the issue:

program shlissue;
var
   MemoryAddress : pointer;
   aWord : word;
begin
   aWord := $1000;
   pByte(MemoryAddress)^ := aWord shr 8;
end.

This compiles fine with your patch, shows the issue when compiled with unpatched fpc trunk

Strange that you could not see the issue with -O1

I have also included an lpi file. When I open the lpi file in Lazarus it shows me optimizations set as O1. When I call lazbuild with --verbose then I get:

CmdLine="/usr/local/bin/fpc  -Tembedded -Parm -MObjFPC -Scgi -Ch8192 -Cs8192 -O1 -gw2 -l -vewnhibq -Fi/Users/ring/devel/mbf/Source -Fi/Users/ring/devel/mbf/Samples/shlissue/lib/arm-embedded -Fu/Users/ring/devel/mbf/Source
-Fu/Users/ring/devel/mbf/Samples/shlissue/
-FU/Users/ring/devel/mbf/Samples/shlissue/lib/arm-embedded/ -FE/Users/ring/devel/mbf/Samples/shlissue/
-o/Users/ring/devel/mbf/Samples/shlissue/shlissue -Cparmv7em -XParm-none-eabi- -Wpnucleof401re -dnucleof401re shlissue.lpr"

Thany you (again and again) for your help!

Michael