[sdcc-devel] [ sdcc-Bugs-1759839 ] variables located in same place as actively-used registers

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Bugs item #1759839, was opened at 2007-07-24 13:11
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: TParker (tparker_silabs)
Assigned to: Nobody/Anonymous (nobody)
Summary: variables located in same place as actively-used registers

Initial Comment:
Version 2.7
Build output (using Silicon Labs IDE):


Invoking project defined compiler.
c:\SDCC\BIN\SDCC.EXE  -c --debug --use-stdout -V  -IM:\PRIVATE\an219\sdcc_bug M:\PRIVATE\an219\sdcc_bug\F360_Blinky.c 
.................
+ c:\SDCC\BIN\sdcpp.exe -nostdinc -Wall -std=c99 -I"M:\PRIVATE\an219\sdcc_bug" -obj-ext=.rel -DSDCC_MODEL_SMALL -DSDCC=270 -DSDCC_mcs51 -D__mcs51 -I"c:\SDCC\BIN\..\include\mcs51" -I"c:\SDCC\BIN\..\include"  "M:\PRIVATE\an219\sdcc_bug\F360_Blinky.c" 
+ c:\SDCC\BIN\asx8051.exe -plosgffc "F360_Blinky.asm"

Link in progress...
c:\SDCC\BIN\SDCC.EXE  --debug --use-stdout -V  -IM:\PRIVATE\an219\sdcc_bug -oM:\PRIVATE\an219\sdcc_bug\F360_Blinky.hex M:\PRIVATE\an219\sdcc_bug\F360_Blinky.rel  
..........
+ c:\SDCC\BIN\aslink.exe -nf "M:\PRIVATE\an219\sdcc_bug\F360_Blinky.lnk"


Problem:

The "using" directive switches to the correct register bank in the ISR.  However, the SDCC Linker is still allocating variables to those DRAM areas so that any instructions using those registers overwrite the variables in DRAM.

Using the attached program for a C8051F36x Target Board, the map file for the DRAM segment looks like this:

Hexadecimal

Area                               Addr   Size   Decimal Bytes (Attributes)
--------------------------------   ----   ----   ------- ----- ------------
DSEG                               0000   0080 =    128. bytes (REL,CON)

      Value  Global
   --------  --------------------------------
     0008    G$phase_add1$0$0
     0008    _phase_add1
     000A    G$phase_add2$0$0
     000A    _phase_add2
     000C    LTimer2_ISR$phase_acc1$1$1
     000E    LTimer2_ISR$phase_acc2$1$1

The variables <phase_add1> and <phase_add2> are global constants that are added to <phase_acc1> and <phase_acc2> in the Timer2 ISR.  However, <phase_add1> and <phase_add2> are located by the linker in Register Bank 1, the same Register Bank specified to be used by the ISR by the "using" directive.  Because of this, the <add> variables are overwritten by the process of adding them to the accumulator variables.

Please contact me if you have any questions at tab...@si....  The attached file requires "compiler_defs.h" and "C8051F360_defs.h" to compile, but it seems like I can only upload the one file.

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