Code generation error extracted from powerpc compiler crash
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## Summary
<!-- Summarize the bug encountered concisely -->
This is a code simplification of the crash that arises inside the trunk powerpc compiler,
when compiled with `-O4` option.
## System Information
<!-- The more information are provided the easier it is to replicate the bug -->
- **Operating system:** Probably any <!-- Windows, Linux (if possible, also name the distro), FreeBSD, Android, ... -->
- **Processor architecture:** Probably several (at least `x86_64` and `aarch64`)<!-- x86, x86-64, ARM, AARCH64, AVR, RISC-V, PowerPC, ... -->
- **Compiler version:** trunk specific <!-- 3.2, 3.2.2, 3.3, trunk, beta, ... (if possible, give also the git hash) -->
## Steps to reproduce
<!-- How one can reproduce the issue - this is very important! -->
See example below.
## Example Project
<!-- If possible, please create an example project that exhibits the problematic
behavior, and link to it here in the bug report. -->
```
muller@cfarm136:~/pas/check$ cat tw-powerpc-crash.pp
{$mode objfpc}
type
TRegister = (R_NO,R_R0,R_R1);
TModuleSwitch = (cs_create_smart);
TModuleSwitches = Set of TModuleSwitch;
TCurrentSettings = record
moduleSwitches : TModuleSwitches;
end;
AFlags = (af_smartlink_sections);
TFlags = (tf_smartlink_sections,tf_smartlink_library);
TTargetInfoFlags = Set of TFlags;
TTargetAsmFlags = Set of AFlags;
TSystem = (system_powerpc_linux,system_powerpc_darwin);
TTargetInfo = record
system : TSystem;
flags : TTargetInfoFlags;
end;
TTargetAsm = record
flags : TTargetAsmFlags;
end;
const
LowRegIndex=longint(low(TRegister));
HighRegIndex=longint(high(TRegister));
gas_regname_short_table : array[LowRegIndex..HighRegIndex] of string[5] = ('NO','0','1');
gas_regname_table : array[LowRegIndex..HighRegIndex] of string[5] = ('NO','R0','R1');
generic_regname : array[LowRegIndex..HighRegIndex] of string[5] = ('zero','one','two');
var
target_asm : TTargetAsm;
target_info : TTargetInfo;
current_settings : TCurrentSettings;
function create_smartlink_sections:boolean;inline;
begin
result:=(af_smartlink_sections in target_asm.flags) and
(tf_smartlink_sections in target_info.flags);
end;
function create_smartlink_library:boolean;inline;
begin
result:=(cs_Create_smart in current_settings.moduleswitches) and
(tf_smartlink_library in target_info.flags) and
not create_smartlink_sections;
end;
function create_smartlink:boolean;inline;
begin
result:=(
(af_smartlink_sections in target_asm.flags) and
(tf_smartlink_sections in target_info.flags)
) or
(
(cs_Create_smart in current_settings.moduleswitches) and
(tf_smartlink_library in target_info.flags)
);
end;
function findreg_by_number(r: TRegister) : longint;
begin
if (R=R_NO) then
result:=0
else if (R=R_R0) then
result:=1
else if (R=R_R1) then
result:=2
else
result:=-1;
end;
function gas_regname(r:Tregister):string;
var
p : longint;
begin
p:=findreg_by_number(r);
if p<>0 then
{The GNU assembler only accepts numbers and no full register names (at least in older versions). To
make the assembler code more readable, we define macros at the start of all assembler files we write
to redefine r1..r31 and f1..f31 to 1..31, and then use the full register names.
However, we do not do this for smart linked files since that would cause a lot of (mostly useless)
overhead. In theory, we could also not do it if "-a" is not used. The Mac OS X assembler (which is
based on GNU as) "natively" supports full register names.}
if create_smartlink_library and
(target_info.system <> system_powerpc_darwin) then
result:=gas_regname_short_table[p]
else
result:=gas_regname_table[p]
else
result:=generic_regname[p];
end;
begin
target_info.system:=system_powerpc_linux;
writeln('Reg name (0)=',gas_regname(R_R0));
writeln('Reg name (1)=',gas_regname(R_R1));
end.
```
## What is the current bug behavior?
<!-- What actually happens -->
Compile with trunk compiler:
```
fpc -gwl -O2 tw-powerpc-crash.pp
```
Run the generated program:
```
muller@cfarm136:~/pas/check$ ./tw-powerpc-crash
Runtime error 216 at $00000000004011B2
$00000000004011B2 GAS_REGNAME, line 97 of tw-powerpc-crash.pp
```
## What is the expected (correct) behavior?
<!-- What you should see instead -->
The compiled code should finish without crash as when compiled with `-O-` option.
issue
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