[fpc-pascal] issue when enabling -O2

[Matias Vara]

Hello everyone,

I am getting an exception when I enable the -O2 optimization. More
precisaily, the line that stars with write_portd.... is corrupting the data
section. This is the pascal code:

function PciReadDword(const bus, device, func, regnum: UInt32): UInt32;
var
  Send: DWORD;
begin
  Send := $80000000 or (bus shl 16) or (device shl 11) or (func shl 8) or
(regnum shl 2);
  write_portd(@Send, PCI_CONF_PORT_INDEX);
  read_portd(@Send, PCI_CONF_PORT_DATA);
  Result := Send;
end;

*which generates (without -02):*

.section
.text.n_arch_$$_pcireaddword$longword$longword$longword$longword$$longword,"x"
.balign 16,0x90
.globl ARCH_$$_PCIREADDWORD$LONGWORD$LONGWORD$LONGWORD$LONGWORD$$LONGWORD
ARCH_$$_PCIREADDWORD$LONGWORD$LONGWORD$LONGWORD$LONGWORD$$LONGWORD:
.Lc207:
.seh_proc ARCH_$$_PCIREADDWORD$LONGWORD$LONGWORD$LONGWORD$LONGWORD$$LONGWORD
.Ll464:
# [992] begin
pushq %rbp
.seh_pushreg %rbp
.Lc209:
.Lc210:
movq %rsp,%rbp
.Lc211:
leaq -80(%rsp),%rsp
.seh_stackalloc 80
.seh_endprologue
# Var bus located at rbp-8, size=OS_32
# Var device located at rbp-16, size=OS_32
# Var func located at rbp-24, size=OS_32
# Var regnum located at rbp-32, size=OS_32
# Var $result located at rbp-40, size=OS_32
# Var Send located at rbp-48, size=OS_32
movl %ecx,-8(%rbp)
movl %edx,-16(%rbp)
movl %r8d,-24(%rbp)
movl %r9d,-32(%rbp)
.Ll465:
# [993] Send := $80000000 or (bus shl 16) or (device shl 11) or (func shl
8) or (regnum shl 2);
movl -8(%rbp),%eax
shll $16,%eax
orl $2147483648,%eax
movl -16(%rbp),%edx
shll $11,%edx
orl %eax,%edx
movl -24(%rbp),%eax
shll $8,%eax
orl %edx,%eax
movl -32(%rbp),%edx
shll $2,%edx
orl %eax,%edx
movl %edx,-48(%rbp)
.Ll466:
# [995] write_portd(@Send, PCI_CONF_PORT_INDEX);
leaq -48(%rbp),%rcx
movl $3320,%edx
call ARCH_$$_WRITE_PORTD$POINTER$WORD
.Ll467:
# [996] read_portd(@Send, PCI_CONF_PORT_DATA);
leaq -48(%rbp),%rcx
movl $3324,%edx
call ARCH_$$_READ_PORTD$POINTER$WORD
.Ll468:
# [997] Result := Send;
movl -48(%rbp),%eax
movl %eax,-40(%rbp)
.Ll469:
# [998] end;
movl -40(%rbp),%eax
nop
leaq (%rbp),%rsp
popq %rbp
ret
.seh_endproc
.Lc208:
.Lt28:
.Ll470:

*and with -O2:*

.section .text.n_arch_$$_pciwriteword$word$word$word$word$word,"x"
.balign 16,0x90
.globl ARCH_$$_PCIWRITEWORD$WORD$WORD$WORD$WORD$WORD
ARCH_$$_PCIWRITEWORD$WORD$WORD$WORD$WORD$WORD:
.Lc148:
# Temps allocated between rbp-16 and rbp-8
.seh_proc ARCH_$$_PCIWRITEWORD$WORD$WORD$WORD$WORD$WORD
.Ll471:
# [1014] begin
pushq %rbp
.seh_pushreg %rbp
.Lc150:
.Lc151:
movq %rsp,%rbp
.Lc152:
leaq -48(%rsp),%rsp
.seh_stackalloc 48
# Var bus located in register ax
# Var device located in register dx
# Var func located in register r8w
# Var regnum located in register r9w
# Var value located in register cx
movq %rbx,-16(%rbp)
.seh_savereg %rbx, 32
.seh_endprologue
# Var Send located at rbp-8, size=OS_32
movw %cx,%ax
movw 48(%rbp),%bx
# PeepHole Optimization,var11
.Ll472:
# [1015] Send := $80000000 or (bus shl 16) or (device shl 11) or (func shl
8) or (regnum and $fc);
andl $65535,%eax
shll $16,%eax
orl $2147483648,%eax
# PeepHole Optimization,var11
andl $65535,%edx
shll $11,%edx
orl %eax,%edx
# PeepHole Optimization,var11
andl $65535,%r8d
shll $8,%r8d
orl %edx,%r8d
# PeepHole Optimization,var1
# PeepHole Optimization,var11
andl $252,%r9d
orl %r8d,%r9d
movl %r9d,-8(%rbp)
.Ll473:
# [1016] write_portd(@Send, PCI_CONF_PORT_INDEX);
leaq -8(%rbp),%rcx
movl $3320,%edx
call ARCH_$$_WRITE_PORTD$POINTER$WORD
.Ll474:
# [1017] write_portw(value, PCI_CONF_PORT_DATA);
movw %bx,%cx
# Var value located in register cx
# PeepHole Optimization,var11
andl $65535,%ecx
movl $3324,%edx
call ARCH_$$_WRITE_PORTW$WORD$WORD
.Ll475:
# [1018] end;
movq -16(%rbp),%rbx
leaq (%rbp),%rsp
popq %rbp
ret
.seh_endproc

The first thing that I realize was the the optimized version is not
generating the correct source when is exiting since it should return
"Send", but am I right? The assembler code of write_portd remains the same,
Am I missing something?

Regards, Matias.
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