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Patch by David Meyer to avoid a O(N^2) behaviour when relaxing fragments.

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Since we now don't update addresses so early, we might relax a bit more than
we need to. This is simillar to the issue in PR8467.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121856 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2010-12-15 07:39:29 +00:00
parent 9448184b99
commit f9a4476173
2 changed files with 10 additions and 7 deletions
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7
lib/MC/MCAssembler.cpp
View File

@ -738,6 +738,7 @@ bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
bool WasRelaxed = false;
for (iterator it = begin(), ie = end(); it != ie; ++it) {
MCSectionData &SD = *it;
MCFragment *FirstInvalidFragment = NULL;
for (MCSectionData::iterator it2 = SD.begin(),
ie2 = SD.end(); it2 != ie2; ++it2) {
@ -762,10 +763,12 @@ bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
break;
}
// Update the layout, and remember that we relaxed.
if (relaxedFrag)
Layout.Invalidate(it2);
if (relaxedFrag && !FirstInvalidFragment)
FirstInvalidFragment = it2;
WasRelaxed |= relaxedFrag;
}
if (FirstInvalidFragment)
Layout.Invalidate(FirstInvalidFragment);
}
return WasRelaxed;

10
test/MC/MachO/relax-recompute-align.s
View File

@ -3,16 +3,16 @@
// FIXME: This is a horrible way of checking the output, we need an llvm-mc
// based 'otool'.
// This is a case where llvm-mc computes a better layout than Darwin 'as'. This
// issue is that after the first jmp slides, the .align size must be
// recomputed -- otherwise the second jump will appear to be out-of-range for a
// 1-byte jump.
// FIXME: PR8467.
// There is an unnecessary relaxation here. After the first jmp slides,
// the .align size could be recomputed so that the second jump will be in range
// for a 1-byte jump. For performance reasons, this is not currently done.
// CHECK: # Section 0
// CHECK: (('section_name', '__text\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
// CHECK: ('segment_name', '__TEXT\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
// CHECK: ('address', 0)
// CHECK: ('size', 306)
// CHECK: ('size', 322)
// CHECK: ('offset', 324)
// CHECK: ('alignment', 4)
// CHECK: ('reloc_offset', 0)