Hi Karol and thanks you very much! I got confused with the function names, I feel very sorry. As I said in my previous email, I fixed by rewriting the assembler function. However, I don't why it worked. So I understand you correctly, if I use assembler in my procedures there could be a risk that I trash a variable that the compiler is using. Is the compiler warning me about this?
Matias 2018-01-10 17:14 GMT+01:00 Karoly Balogh (Charlie/SGR) < char...@scenergy.dfmk.hu>: > Hi, > > On Wed, 10 Jan 2018, Matias Vara wrote: > > > 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: > > > > (***shipp***) > > > > 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: > > > > 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? > > The -O2 version of the function you sent is from a different one, it's > from a Write function, not a Read... So no wonder it doesn't return > anything... :) > > BTW, -O2 uses register variables, while -O- doesn't. If your assembler > trashes one of them without preserving one, it can lead to crashes... > But there could be many other reasons. > > Without seeing the actual assembler functions it's hard to tell. > > Charlie > _______________________________________________ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal >
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