Okay, so I have to specify "-MObjfpc -Sh" to get it to compile due to
what the code uses, and the bug still requires the use of -O2 to
appear. However... "fpc -MObjfpc -Sh -O2 -Ooregvar -alr -sr breakp.pp"
produces a bad binary.
I removed the register comments so it's clearer:
...
# [11] pChar(result)[i] := BarSym[(progress >= (0.75 + i) / divs) or (i
= int32(divs) - 1) and (progress >= 1)];
cvtsi2ssl %ireg16d,%mreg34ms
movaps %mreg34ms,%mreg35ms
addss _$BREAKP$_Ld1(%rip),%mreg35ms
movl %ireg18d,%ireg28d
andl $4294967295,%ireg28d
cvtsi2ssq %ireg28q,%mreg37ms
movaps %mreg35ms,%mreg38ms
divss %mreg37ms,%mreg38ms
comiss %mreg32ms,%mreg38ms
jp .Lj12
jbe .Lj10 <---- Register %ireg27q not initialised if this
instruction branches to .Lj10
.Lj12:
jmp .Lj11
.Lj11:
movl %ireg18d,%ireg29d
movslq %ireg29d,%ireg30q
subq $1,%ireg30q
movslq %ireg16d,%ireg31q
movq %ireg31q,%ireg27q <---- Problem register: %ireg27q
cmpq %ireg27q,%ireg30q
je .Lj14
jmp .Lj15
.Lj14:
comiss _$BREAKP$_Ld2(%rip),%mreg32ms
jp .Lj17
jae .Lj16
.Lj17:
jmp .Lj15
.Lj16:
jmp .Lj10
.Lj15:
jmp .Lj13
.Lj10:
movq $1,%ireg32q
jmp .Lj18
.Lj13:
movq $0,%ireg32q
.Lj18:
movq (%ireg17q),%ireg33q
cmpq $0,%ireg33q
jne .Lj19
leaq FPC_EMPTYCHAR(%rip),%ireg33q
.Lj19:
leaq
TC_$P$BREAKP$_$BAR$SINGLE$LONGWORD$$ANSISTRING_$$_BARSYM(%rip),%ireg34q
movb (%ireg34q,%ireg32q,1),%ireg35l
movb %ireg35l,(%ireg33q,%ireg27q,1) <---- Problem register: %ireg27q
cmpl %ireg25d,%ireg16d
jge .Lj9
jmp .Lj7
.Lj9:
.Lj6:
...
The problem register is %ireg27q - it's not being initialised if "jbe
.Lj10" branches. By your explanation, it seems that the code generator
is buggy on one of the nodes. Thanks for the tips in isolating where it
could be. To help out, I've attached the node dump file for the test
program.
Gareth aka. Kit
On 26/11/2020 19:04, Yuriy Sydorov via fpc-devel wrote:
Hi,
On 26.11.2020 17:34, J. Gareth Moreton via fpc-devel wrote:
Hi everyone,
So a couple of people have reported that -O2 sometimes produces bad
code under x86_64. So far it seems isolated to that CPU.
https://bugs.freepascal.org/view.php?id=38129
After my own investigations with the attached code, the problem still
occurs even if the peephole optimizer is disabled, and the
uninitialised register is being allocated within conditional code
that is not always executed, rather than before or after it.
Anyone with any tips on where to dig next (register allocator, node
converter etc.) would be most appreciated!
First compile with the "-Ooregvar -alr -sr" switches. You will get the
assembler output with imaginary registers and notes about register
allocations and de-allocations. Inspect if all is correct at this
stage. If not then the a code generator of some node is buggy.
Then compile with "-Ooregvar -alr". If the issue is present only at
this stage, then the bug is in the register allocator.
Yuriy.
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<?xml version="1.0" encoding="utf-8"?>
<program name="breakp">
<subroutine name="Bar(<var AnsiString>;const Single;LongWord):AnsiString(0);">
<returndef>AnsiString</returndef>
<code>
<blockn resultdef="$void" pos="8,1" complexity="255">
<statementn pos="9,28" complexity="255">
<inlinen resultdef="$void" pos="9,5" complexity="255" inlinenumber="in_setlength_x">
<callparan resultdef="LongWord" pos="9,27" complexity="2">
<typeconvn resultdef="Int64" pos="9,27" complexity="1" convtype="tc_int_2_int">
<loadn resultdef="LongWord" pos="9,27" complexity="0">
<symbol>DIVS</symbol>
</loadn>
</typeconvn>
</callparan>
<callparan resultdef="AnsiString" pos="9,21" complexity="2">
<typeconvn resultdef="AnsiString" pos="9,21" flags="nf_absolute" complexity="1" convtype="tc_equal">
<loadn resultdef="AnsiString" pos="9,21" flags="nf_write" complexity="1">
<symbol>result</symbol>
</loadn>
</typeconvn>
</callparan>
</inlinen>
</statementn>
<statementn pos="11,113" complexity="255">
<forn resultdef="$void" pos="10,5" complexity="255" loopflags="lnf_testatbegin,lnf_dont_mind_loopvar_on_exit">
<counter>
<loadn resultdef="LongInt" pos="10,9" flags="nf_write" complexity="0">
<symbol>I</symbol>
</loadn>
</counter>
<first>
<ordconstn resultdef="LongInt" pos="10,14" complexity="0" rangecheck="FALSE">
<value>0</value>
</ordconstn>
</first>
<last>
<subn resultdef="LongInt" pos="10,31" complexity="1">
<typeconvn resultdef="LongInt" pos="10,19" flags="nf_explicit" complexity="0" convtype="tc_int_2_int">
<loadn resultdef="LongWord" pos="10,25" complexity="0">
<symbol>DIVS</symbol>
</loadn>
</typeconvn>
<ordconstn resultdef="LongInt" pos="10,33" flags="nf_explicit" complexity="0" rangecheck="FALSE">
<value>1</value>
</ordconstn>
</subn>
</last>
<assignn resultdef="$void" pos="11,9" complexity="2">
<vecn resultdef="Char" pos="11,22" flags="nf_write,nf_callunique" complexity="5">
<typeconvn resultdef="<no type symbol>" pos="11,9" complexity="3" convtype="tc_pointer_2_array">
<typeconvn resultdef="PChar" pos="11,9" flags="nf_explicit" complexity="2" convtype="tc_ansistring_2_pchar">
<typeconvn resultdef="AnsiString" pos="11,15" flags="nf_absolute" complexity="1" convtype="tc_equal">
<loadn resultdef="AnsiString" pos="11,21" flags="nf_write" complexity="1">
<symbol>result</symbol>
</loadn>
</typeconvn>
</typeconvn>
</typeconvn>
<index>
<typeconvn resultdef="Int64" pos="11,23" complexity="1" convtype="tc_int_2_int">
<loadn resultdef="LongInt" pos="11,23" complexity="0">
<symbol>I</symbol>
</loadn>
</typeconvn>
</index>
</vecn>
<vecn resultdef="Char" pos="11,35" complexity="2">
<loadn resultdef="<no type symbol>" pos="11,29" complexity="1">
<symbol>BARSYM</symbol>
</loadn>
<index>
<orn resultdef="Boolean" pos="11,68" complexity="2">
<gten resultdef="Boolean" pos="11,36" complexity="17">
<loadn resultdef="Single" pos="11,37" complexity="0">
<symbol>PROGRESS</symbol>
</loadn>
<slashn resultdef="Single" pos="11,60" complexity="16">
<addn resultdef="Single" pos="11,49" complexity="4">
<realconstn resultdef="Single" pos="11,50" complexity="2">
<value> 7.5000000000000000E-001</value>
</realconstn>
<typeconvn resultdef="Single" pos="11,57" complexity="1" convtype="tc_int_2_real">
<loadn resultdef="LongInt" pos="11,57" complexity="0">
<symbol>I</symbol>
</loadn>
</typeconvn>
</addn>
<typeconvn resultdef="Single" pos="11,62" complexity="1" convtype="tc_int_2_real">
<loadn resultdef="LongWord" pos="11,62" complexity="0">
<symbol>DIVS</symbol>
</loadn>
</typeconvn>
</slashn>
</gten>
<andn resultdef="Boolean" pos="11,93" complexity="2">
<equaln resultdef="Boolean" pos="11,71" complexity="4">
<typeconvn resultdef="Int64" pos="11,72" complexity="1" convtype="tc_int_2_int">
<loadn resultdef="LongInt" pos="11,72" complexity="0">
<symbol>I</symbol>
</loadn>
</typeconvn>
<subn resultdef="Int64" pos="11,88" complexity="2">
<typeconvn resultdef="Int64" pos="11,76" complexity="1" convtype="tc_int_2_int">
<typeconvn resultdef="LongInt" pos="11,76" flags="nf_explicit" complexity="0" convtype="tc_int_2_int">
<loadn resultdef="LongWord" pos="11,82" complexity="0">
<symbol>DIVS</symbol>
</loadn>
</typeconvn>
</typeconvn>
<ordconstn resultdef="Int64" pos="11,90" complexity="0" rangecheck="FALSE">
<value>1</value>
</ordconstn>
</subn>
</equaln>
<gten resultdef="Boolean" pos="11,97" complexity="2">
<loadn resultdef="Single" pos="11,98" complexity="0">
<symbol>PROGRESS</symbol>
</loadn>
<realconstn resultdef="Single" pos="11,110" complexity="2">
<value> 1.0000000000000000E+000</value>
</realconstn>
</gten>
</andn>
</orn>
</index>
</vecn>
</assignn>
</forn>
</statementn>
</blockn>
</code>
</subroutine>
<subroutine type="initialization" name="$main; Register;" convention="Register">
<code>
<blockn resultdef="$void" pos="17,1" complexity="255">
<statementn pos="18,31" complexity="255">
<assignn resultdef="$void" pos="18,5" complexity="255">
<loadn resultdef="AnsiString" pos="18,5" flags="nf_write" complexity="1">
<symbol>S</symbol>
</loadn>
<addn resultdef="AnsiString" pos="18,23" complexity="255">
<calln resultdef="AnsiString" pos="18,10" complexity="255">
<procname>Bar(<var AnsiString>;const Single;LongWord):AnsiString(0);</procname>
<callparan resultdef="LongWord" pos="18,21" complexity="1">
<ordconstn resultdef="LongWord" pos="18,21" complexity="0" rangecheck="FALSE">
<value>10</value>
</ordconstn>
</callparan>
<callparan resultdef="Single" pos="18,17" complexity="2">
<realconstn resultdef="Single" pos="18,17" complexity="2">
<value> 6.9999998807907104E-001</value>
</realconstn>
</callparan>
<callparan pos="18,10" complexity="1">
<nothingn resultdef="$void" pos="18,10" complexity="0" />
</callparan>
</calln>
<stringconstn resultdef="AnsiString" pos="18,25" complexity="1">
<stringtype>ansistring</stringtype>
<length>4</length>
<value> 70%</value>
</stringconstn>
</addn>
</assignn>
</statementn>
<statementn pos="19,15" complexity="255">
<blockn resultdef="$void" pos="19,5" complexity="255">
<statementn pos="19,5" complexity="255">
<nothingn resultdef="$void" pos="19,5" complexity="0" />
</statementn>
<statementn pos="19,5" complexity="255">
<tempcreaten resultdef="$void" pos="19,5" complexity="0" id="$211A6C00">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
<size>8</size>
<tempinit />
</tempcreaten>
</statementn>
<statementn pos="19,5" complexity="255">
<assignn resultdef="$void" pos="19,5" complexity="255">
<temprefn resultdef="Pointer" pos="19,5" flags="nf_write" complexity="1" id="$211A6C00">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
<typeconvn resultdef="Pointer" pos="19,5" complexity="255" convtype="tc_equal">
<calln resultdef="PText" pos="19,5" complexity="255">
<procname>$fpc_get_output:^Text;</procname>
</calln>
</typeconvn>
</assignn>
</statementn>
<statementn pos="19,5" complexity="255">
<calln resultdef="$void" pos="19,5" complexity="255">
<procname>$fpc_write_text_ansistr(LongInt;var Text;const RawByteString);</procname>
<callparan resultdef="RawByteString" pos="19,14" complexity="2">
<loadn resultdef="RawByteString" pos="19,14" complexity="1">
<symbol>S</symbol>
</loadn>
</callparan>
<callparan resultdef="Text" pos="19,5" complexity="1">
<typeconvn resultdef="Text" pos="19,5" flags="nf_explicit,nf_internal" complexity="1" convtype="tc_equal">
<derefn resultdef="$void" pos="19,5" complexity="1">
<temprefn resultdef="Pointer" pos="19,5" complexity="1" id="$211A6C00">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
</derefn>
</typeconvn>
</callparan>
<callparan resultdef="LongInt" pos="19,5" complexity="1">
<ordconstn resultdef="LongInt" pos="19,5" complexity="0" rangecheck="FALSE">
<value>0</value>
</ordconstn>
</callparan>
</calln>
</statementn>
<statementn pos="19,5" complexity="255">
<calln resultdef="$void" pos="19,5" complexity="255">
<procname>$fpc_writeln_end(var Text);</procname>
<callparan resultdef="Text" pos="19,5" complexity="1">
<typeconvn resultdef="Text" pos="19,5" flags="nf_explicit,nf_internal" complexity="1" convtype="tc_equal">
<derefn resultdef="$void" pos="19,5" complexity="1">
<temprefn resultdef="Pointer" pos="19,5" complexity="1" id="$211A6C00">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
</derefn>
</typeconvn>
</callparan>
</calln>
</statementn>
<statementn pos="19,5" complexity="0">
<tempdeleten resultdef="$void" pos="19,5" complexity="0" id="$211A6C00">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
<release_to_normal>FALSE</release_to_normal>
</tempdeleten>
</statementn>
</blockn>
</statementn>
<statementn pos="20,19" complexity="255">
<blockn resultdef="$void" pos="20,5" complexity="255">
<statementn pos="20,5" complexity="255">
<nothingn resultdef="$void" pos="20,5" complexity="0" />
</statementn>
<statementn pos="20,5" complexity="255">
<tempcreaten resultdef="$void" pos="20,5" complexity="0" id="$211A6B80">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
<size>8</size>
<tempinit />
</tempcreaten>
</statementn>
<statementn pos="20,5" complexity="255">
<assignn resultdef="$void" pos="20,5" complexity="255">
<temprefn resultdef="Pointer" pos="20,5" flags="nf_write" complexity="1" id="$211A6B80">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
<typeconvn resultdef="Pointer" pos="20,5" complexity="255" convtype="tc_equal">
<calln resultdef="PText" pos="20,5" complexity="255">
<procname>$fpc_get_output:^Text;</procname>
</calln>
</typeconvn>
</assignn>
</statementn>
<statementn pos="20,5" complexity="255">
<calln resultdef="$void" pos="20,5" complexity="255">
<procname>$fpc_write_text_shortstr(LongInt;var Text;const ShortString);</procname>
<callparan resultdef="ShortString" pos="20,18" complexity="1">
<stringconstn resultdef="ShortString" pos="20,18" complexity="1">
<stringtype>shortstring</stringtype>
<length>3</length>
<value>Odd</value>
</stringconstn>
</callparan>
<callparan resultdef="Text" pos="20,5" complexity="1">
<typeconvn resultdef="Text" pos="20,5" flags="nf_explicit,nf_internal" complexity="1" convtype="tc_equal">
<derefn resultdef="$void" pos="20,5" complexity="1">
<temprefn resultdef="Pointer" pos="20,5" complexity="1" id="$211A6B80">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
</derefn>
</typeconvn>
</callparan>
<callparan resultdef="LongInt" pos="20,5" complexity="1">
<ordconstn resultdef="LongInt" pos="20,5" complexity="0" rangecheck="FALSE">
<value>0</value>
</ordconstn>
</callparan>
</calln>
</statementn>
<statementn pos="20,5" complexity="255">
<calln resultdef="$void" pos="20,5" complexity="255">
<procname>$fpc_writeln_end(var Text);</procname>
<callparan resultdef="Text" pos="20,5" complexity="1">
<typeconvn resultdef="Text" pos="20,5" flags="nf_explicit,nf_internal" complexity="1" convtype="tc_equal">
<derefn resultdef="$void" pos="20,5" complexity="1">
<temprefn resultdef="Pointer" pos="20,5" complexity="1" id="$211A6B80">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
</temprefn>
</derefn>
</typeconvn>
</callparan>
</calln>
</statementn>
<statementn pos="20,5" complexity="0">
<tempdeleten resultdef="$void" pos="20,5" complexity="0" id="$211A6B80">
<typedef>Pointer</typedef>
<tempflags>ti_may_be_in_reg</tempflags>
<temptype>tt_persistent</temptype>
<release_to_normal>FALSE</release_to_normal>
</tempdeleten>
</statementn>
</blockn>
</statementn>
</blockn>
</code>
</subroutine>
</program>
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