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When converting a switch to a lookup table we might have to generate a bitmaks
to encode and check for holes in the original switch statement.
The type of this mask depends on the number of switch statements, which can
result in illegal types for pretty much all architectures.
To avoid unnecessary type legalization and help FastISel this commit increases
the size of the bitmask to next power-of-2 value when necessary.
This fixes rdar://problem/18984639.
llvm-svn: 222168
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This is a simple optimization for switch table lookup:
It computes the output value directly with an (optional) mul and add if there is a linear mapping between index and output.
Example:
int f1(int x) {
switch (x) {
case 0: return 10;
case 1: return 11;
case 2: return 12;
case 3: return 13;
}
return 0;
}
generates:
define i32 @f1(i32 %x) #0 {
entry:
%0 = icmp ult i32 %x, 4
br i1 %0, label %switch.lookup, label %return
switch.lookup:
%switch.offset = add i32 %x, 10
ret i32 %switch.offset
return:
ret i32 0
}
llvm-svn: 222121
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This is the same optimization of r219233 with modifications to support PHIs with multiple incoming edges from the same block
and a test to check that this condition is handled.
llvm-svn: 219656
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llvm-svn: 219587
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This optimization tries to convert switch instructions that are used to select a value with only 2 unique cases + default block
to a select or a couple of selects (depending if the default block is reachable or not).
The typical case this optimization wants to be able to optimize is this one:
Example:
switch (a) {
case 10: %0 = icmp eq i32 %a, 10
return 10; %1 = select i1 %0, i32 10, i32 4
case 20: ----> %2 = icmp eq i32 %a, 20
return 2; %3 = select i1 %2, i32 2, i32 %1
default:
return 4;
}
It also sets the base for further optimizations that are planned and being reviewed.
llvm-svn: 219223
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When we have a covered lookup table, make sure we don't delete PHINodes that
are cached in PHIs.
rdar://17887153
llvm-svn: 214642
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llvm-svn: 213884
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This is a follow-up to r211331, which failed to notice that we were
returning early from ValidLookupTableConstant for GEPs.
llvm-svn: 211753
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We would previously put dllimport variables in switch lookup tables, which
doesn't work because the address cannot be used in a constant initializer.
This is basically the same problem that we have in PR19955.
Putting TLS variables in switch tables also desn't work, because the
address of such a variable is not constant.
Differential Revision: http://reviews.llvm.org/D4220
llvm-svn: 211331
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We can just split targets_to_build in one place and make it immutable.
llvm-svn: 210496
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This allows us to generate table lookups for code such as:
unsigned test(unsigned x) {
switch (x) {
case 100: return 0;
case 101: return 1;
case 103: return 2;
case 105: return 3;
case 107: return 4;
case 109: return 5;
case 110: return 6;
default: return f(x);
}
}
Since cases 102, 104, etc. are not constants, the lookup table has holes
in those positions. We therefore guard the table lookup with a bitmask check.
Patch by Jasper Neumann!
llvm-svn: 203694
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There has been an old FIXME to find the right cut-off for when it's worth
analyzing and potentially transforming a switch to a lookup table.
The switches always have two or more cases. I could not measure any speed-up
by transforming a switch with two cases. A switch with three cases gets a nice
speed-up, and I couldn't measure any compile-time regression, so I think this
is the right threshold.
In a Clang self-host, this causes 480 new switches to be transformed,
and reduces the final binary size with 8 KB.
llvm-svn: 199294
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case when the lookup table doesn't have any holes.
This means we can build a lookup table for switches like this:
switch (x) {
case 0: return 1;
case 1: return 2;
case 2: return 3;
case 3: return 4;
default: exit(1);
}
The default case doesn't yield a constant result here, but that doesn't matter,
since a default result is only necessary for filling holes in the lookup table,
and this table doesn't have any holes.
This makes us transform 505 more switches in a clang bootstrap, and shaves 164 KB
off the resulting clang binary.
llvm-svn: 199025
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Both simpler and more powerful than the hand-rolled folding logic.
llvm-svn: 194475
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- Instead of setting the suffixes in a bunch of places, just set one master
list in the top-level config. We now only modify the suffix list in a few
suites that have one particular unique suffix (.ml, .mc, .yaml, .td, .py).
- Aside from removing the need for a bunch of lit.local.cfg files, this enables
4 tests that were inadvertently being skipped (one in
Transforms/BranchFolding, a .s file each in DebugInfo/AArch64 and
CodeGen/PowerPC, and one in CodeGen/SI which is now failing and has been
XFAILED).
- This commit also fixes a bunch of config files to use config.root instead of
older copy-pasted code.
llvm-svn: 188513
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easier debugging. No functionality change.
This conversion 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/;\(.*\)\([A-Za-z0-9_]*\):\( *\)define\([^@]*\)@$FUNC\([( ]*\)\$/;\1\2-LABEL:\3define\4@$FUNC(/g" $TEMP
done
mv $TEMP $NAME
fi
done
llvm-svn: 186269
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functionality change.
This update was done with the following bash script:
find test/Transforms -name "*.ll" | \
while read NAME; do
echo "$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
llvm-svn: 186268
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the tables cannot fit in registers (i.e. bitmap), do not emit the table
if it's using an illegal type.
rdar://12779436
llvm-svn: 168970
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is available.
llvm-svn: 167552
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