The symptom is that an assertion is triggered. The assertion was added by
me to detect the situation when value is propagated from dead blocks.
(We can certainly get rid of assertion; it is safe to do so, because propagating
value from dead block to alive join node is certainly ok.)
The root cause of this bug is : edge-splitting is conducted on the fly,
the edge being split could be a dead edge, therefore the block that
split the critial edge needs to be flagged "dead" as well.
There are 3 ways to fix this bug:
1) Get rid of the assertion as I mentioned eariler
2) When an dead edge is split, flag the inserted block "dead".
3) proactively split the critical edges connecting dead and live blocks when
new dead blocks are revealed.
This fix go for 3) with additional 2 LOC.
Testing case was added by Rafael the other day.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194424 91177308-0d34-0410-b5e6-96231b3b80d8
The problem of r191017 is that when GVN fabricate a val-number for a dead instruction (in order
to make following expr-PRE happy), it forget to fabricate a leader-table entry for it as well.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191118 91177308-0d34-0410-b5e6-96231b3b80d8
This is how it ignores the dead code:
1) When a dead branch target, say block B, is identified, all the
blocks dominated by B is dead as well.
2) The PHIs of those blocks in dominance-frontier(B) is updated such
that the operands corresponding to dead predecessors are replaced
by "UndefVal".
Using lattice's jargon, the "UndefVal" is the "Top" in essence.
Phi node like this "phi(v1 bb1, undef xx)" will be optimized into
"v1" if v1 is constant, or v1 is an instruction which dominate this
PHI node.
3) When analyzing the availability of a load L, all dead mem-ops which
L depends on disguise as a load which evaluate exactly same value as L.
4) The dead mem-ops will be materialized as "UndefVal" during code motion.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191017 91177308-0d34-0410-b5e6-96231b3b80d8
This update was done with the following bash script:
find test/Transforms -name "*.ll" | \
while read NAME; do
echo "$NAME"
if ! grep -q "^; *RUN: *llc" $NAME; then
TEMP=`mktemp -t temp`
cp $NAME $TEMP
sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \
while read FUNC; do
sed -i '' "s/;\(.*\)\([A-Za-z0-9_]*\):\( *\)@$FUNC\([( ]*\)\$/;\1\2-LABEL:\3@$FUNC(/g" $TEMP
done
mv $TEMP $NAME
fi
done
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186268 91177308-0d34-0410-b5e6-96231b3b80d8
I really need to find a way to automate this, but I can't come up with a regex
that has no false positives while handling tricky cases like custom check
prefixes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162097 91177308-0d34-0410-b5e6-96231b3b80d8
and stores capture) to permit the caller to see each capture point and decide
whether to continue looking.
Use this inside memdep to do an analysis that basicaa won't do. This lets us
solve another devirtualization case, fixing PR8908!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144580 91177308-0d34-0410-b5e6-96231b3b80d8
for pre-2.9 bitcode files. We keep x86 unaligned loads, movnt, crc32, and the
target indep prefetch change.
As usual, updating the testsuite is a PITA.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133337 91177308-0d34-0410-b5e6-96231b3b80d8
redundant with partially-aliasing loads.
When computing what portion of a clobbering load value is needed,
it doesn't consider phi-translation which may have occurred
between the clobbing load and the redundant load.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132631 91177308-0d34-0410-b5e6-96231b3b80d8
a nice and tidy:
%x1 = load i32* %0, align 4
%1 = icmp eq i32 %x1, 1179403647
br i1 %1, label %if.then, label %if.end
instead of doing lots of loads and branches. May the FreeBSD bootloader
long fit in its allocated space.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130416 91177308-0d34-0410-b5e6-96231b3b80d8
wider load would allow elimination of subsequent loads, and when the wider
load is still a native integer type. This eliminates a ton of loads on
various benchmarks involving struct fields, though it is somewhat hobbled
by clang not being very aggressive about field alignment.
This is yet another step along the way towards resolving PR6627.
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translation fails. We were bailing out in some cases that would
cause us to miss GVN'ing some non-local cases away.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130206 91177308-0d34-0410-b5e6-96231b3b80d8
return it as a clobber. This allows GVN to do smart things.
Enhance GVN to be smart about the case when a small load is clobbered
by a larger overlapping load. In this case, forward the value. This
allows us to compile stuff like this:
int test(void *P) {
int tmp = *(unsigned int*)P;
return tmp+*((unsigned char*)P+1);
}
into:
_test: ## @test
movl (%rdi), %ecx
movzbl %ch, %eax
addl %ecx, %eax
ret
which has one load. We already handled the case where the smaller
load was from a must-aliased base pointer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130180 91177308-0d34-0410-b5e6-96231b3b80d8
does normal initialization and normal chaining. Change the default
AliasAnalysis implementation to NoAlias.
Update StandardCompileOpts.h and friends to explicitly request
BasicAliasAnalysis.
Update tests to explicitly request -basicaa.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116720 91177308-0d34-0410-b5e6-96231b3b80d8
clobbers to forward pieces of large stores to small loads, we need to consider
the properly phi translated pointer in the store block.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90978 91177308-0d34-0410-b5e6-96231b3b80d8
stores is not phi translating, thus it miscompiles really
crazy testcases. This is from inspection, I haven't seen
this in the wild.
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phi translation of complex expressions like &A[i+1]. This has the
following benefits:
1. The phi translation logic is all contained in its own class with
a strong interface and verification that it is self consistent.
2. The logic is more correct than before. Previously, if intermediate
expressions got PHI translated, we'd miss the update and scan for
the wrong pointers in predecessor blocks. @phi_trans2 is a testcase
for this.
3. We have a lot less code in memdep.
We can handle phi translation across blocks of things like @phi_trans3,
which is pretty insane :).
This patch should fix the miscompiles of 255.vortex, and I tested it
with a bootstrap of llvm-gcc, llvm-test and dejagnu of course.
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that I'm working on. This is manifesting as a miscompile of 255.vortex
on some targets. No check lines yet because it fails.
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This doesn't kick in too much because of phi translation issues,
but this can be resolved in the future.
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from a piece of a large store when both are in the same block.
This allows clang to compile the testcase in PR4216 to this code:
_test_bitfield:
movl 4(%esp), %eax
movl %eax, %ecx
andl $-65536, %ecx
orl $32962, %eax
andl $40186, %eax
orl %ecx, %eax
ret
This is not ideal, but is a whole lot better than the code produced
by llvm-gcc:
_test_bitfield:
movw $-32574, %ax
orw 4(%esp), %ax
andw $-25350, %ax
movw %ax, 4(%esp)
movw 7(%esp), %cx
shlw $8, %cx
movzbl 6(%esp), %edx
orw %cx, %dx
movzwl %dx, %ecx
shll $16, %ecx
movzwl %ax, %eax
orl %ecx, %eax
ret
and dramatically better than that produced by gcc 4.2:
_test_bitfield:
pushl %ebx
call L3
"L00000000001$pb":
L3:
popl %ebx
movl 8(%esp), %eax
leal 0(,%eax,4), %edx
sarb $7, %dl
movl %eax, %ecx
andl $7168, %ecx
andl $-7201, %ebx
movzbl %dl, %edx
andl $1, %edx
sall $5, %edx
orl %ecx, %ebx
orl %edx, %ebx
andl $24, %eax
andl $-58336, %ebx
orl %eax, %ebx
orl $32962, %ebx
movl %ebx, %eax
popl %ebx
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82439 91177308-0d34-0410-b5e6-96231b3b80d8
early for the stated reasons: this allows it to find more
equivalences and depend less on code layout.
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so that nonlocal and partially redundant loads can use it as well.
The testcase shows examples of craziness this can handle. This triggers
*many* times in 176.gcc.
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(and load -> load) when the base pointers must alias but when
they are different types. This occurs very very frequently in
176.gcc and other code that uses bitfields a lot.
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