to go in. This patch allows us to compute the trip count of loops controlled
by values loaded from constant arrays. The cannonnical example of this is
strlen when passed a constant argument:
for (int i = 0; "constantstring"[i]; ++i) ;
return i;
In this case, it will compute that the loop executes 14 times, which means
that the exit value of i is 14. Because of this, the loop gets DCE'd and
we are happy. This also applies to anything that does similar things, e.g.
loops like this:
const float Array[] = { 0.1, 2.1, 3.2, 23.21 };
for (int i = 0; Array[i] < 20; ++i)
and is actually fairly general.
The problem with this is that it almost never triggers. The reason is that
we run indvars and the loop optimizer only at compile time, which is before
things like strlen and strcpy have been inlined into the program from libc.
Because of this, it almost never is used (it triggers twice in specint2k).
I'm committing it because it DOES work, may be useful in the future, and
doesn't slow us down at all. If/when we start running the loop optimizer
at link-time (-O4?) this will be very nice indeed :)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16926 91177308-0d34-0410-b5e6-96231b3b80d8
pointer recurrences into expressions from this:
%P_addr.0.i.0 = phi sbyte* [ getelementptr ([8 x sbyte]* %.str_1, int 0, int 0), %entry ], [ %inc.0.i, %no_exit.i ]
%inc.0.i = getelementptr sbyte* %P_addr.0.i.0, int 1 ; <sbyte*> [#uses=2]
into this:
%inc.0.i = getelementptr sbyte* getelementptr ([8 x sbyte]* %.str_1, int 0, int 0), int %inc.0.i.rec
Actually create something nice, like this:
%inc.0.i = getelementptr [8 x sbyte]* %.str_1, int 0, int %inc.0.i.rec
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16924 91177308-0d34-0410-b5e6-96231b3b80d8
well as a vector of constant*'s. It turns out that this is more efficient
and all of the clients want to do that, so we should cater to them.
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First, it allows SRA of globals that have embedded arrays, implementing
GlobalOpt/globalsra-partial.llx. This comes up infrequently, but does allow,
for example, deleting several stores to dead parts of globals in dhrystone.
Second, this implements GlobalOpt/malloc-promote-*.llx, which is the
following nifty transformation:
Basically if a global pointer is initialized with malloc, and we can tell
that the program won't notice, we transform this:
struct foo *FooPtr;
...
FooPtr = malloc(sizeof(struct foo));
...
FooPtr->A FooPtr->B
Into:
struct foo FooPtrBody;
...
FooPtrBody.A FooPtrBody.B
This comes up occasionally, for example, the 'disp' global in 183.equake (where
the xform speeds the CBE version of the program up from 56.16s to 52.40s (7%)
on apoc), and the 'desired_accept', 'fixLRBT', 'macroArray', & 'key_queue'
globals in 300.twolf (speeding it up from 22.29s to 21.55s (3.4%)).
The nice thing about this xform is that it exposes the resulting global to
global variable optimization and makes alias analysis easier in addition to
eliminating a few loads.
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first element of an array, return a GEP instead of a cast. This allows us
to transparently fold this:
int* getelementptr (int* cast ([100 x int]* %Gbody to int*), int 40)
into this:
int* getelementptr ([100 x int]* %Gbody, int 0, int 40)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16911 91177308-0d34-0410-b5e6-96231b3b80d8
still optimize away all of the indirect calls and loads, etc from it.
This turns code like this:
if (G != 0)
G();
into
if (G != 0)
ActualCallee();
This triggers a couple of times in gcc and libstdc++.
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argument values passed in (so they're not dead until *after* the call),
and callees are free to modify those registers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16882 91177308-0d34-0410-b5e6-96231b3b80d8
Deal with allocating stack space for outgoing args and copying them into the
correct stack slots (at least, we can copy <=32-bit int args).
We now correctly generate ADJCALLSTACK* instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16881 91177308-0d34-0410-b5e6-96231b3b80d8
stored to, but are stored at variable indexes. This occurs at least in
176.gcc, but probably others, and we should handle it for completeness.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16876 91177308-0d34-0410-b5e6-96231b3b80d8
has a large number of users. Instead, just keep track of whether we're
making changes as we do so.
This patch has no functionlity changes.
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we know that all uses of the global will trap if the pointer contained is
null. In this case, we forward substitute the stored value to any uses.
This has the effect of devirtualizing trivial globals in trivial cases. For
example, 164.gzip contains this:
gzip.h:extern int (*read_buf) OF((char *buf, unsigned size));
bits.c: read_buf = file_read;
deflate.c: lookahead = read_buf((char*)window,
deflate.c: n = read_buf((char*)window+strstart+lookahead, more);
Since read_buf has to point to file_read at every use, we just replace
the calls through read_buf with a direct call to file_read.
This occurs in several benchmarks, including 176.gcc and 164.gzip. Direct
calls are good and stuff.
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the -sse* options (to avoid misleading people).
Also, the stack alignment of the target doesn't depend on whether SSE is
eventually implemented, so remove a comment.
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which prevented setcc's from being folded into branches. It appears that
conditional branchinst's CC operand is actually operand(2), not operand(0)
as we might expect. :(
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* Do not lead dangling dead constants prevent optimization
* Iterate global optimization while we're making progress.
These changes allow us to be more aggressive, handling cases like
GlobalOpt/iterate.llx without a problem (turning it into 'ret int 0').
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16857 91177308-0d34-0410-b5e6-96231b3b80d8
optimizations to trigger much more often. This allows the elimination of
several dozen more global variables in Programs/External. Note that we only
do this for non-constant globals: constant globals will already be optimized
out if the accesses to them permit it.
This implements Transforms/GlobalOpt/globalsra.llx
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16842 91177308-0d34-0410-b5e6-96231b3b80d8
of one or more 1 bits (may wrap from least significant bit to most
significant bit) as the rlwinm rather than andi., andis., or some longer
instructons sequence.
int andn4(int z) { return z & -4; }
int clearhi(int z) { return z & 0x0000FFFF; }
int clearlo(int z) { return z & 0xFFFF0000; }
int clearmid(int z) { return z & 0x00FFFF00; }
int clearwrap(int z) { return z & 0xFF0000FF; }
_andn4:
rlwinm r3, r3, 0, 0, 29
blr
_clearhi:
rlwinm r3, r3, 0, 16, 31
blr
_clearlo:
rlwinm r3, r3, 0, 0, 15
blr
_clearmid:
rlwinm r3, r3, 0, 8, 23
blr
_clearwrap:
rlwinm r3, r3, 0, 24, 7
blr
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1. Fix an illegal argument to getClassB when deciding whether or not to
sign extend a byte load.
2. Initial addition of isLoad and isStore flags to the instruction .td file
for eventual use in a scheduler.
3. Rewrite of how constants are handled in emitSimpleBinaryOperation so
that we can emit the PowerPC shifted immediate instructions far more
often. This allows us to emit the following code:
int foo(int x) { return x | 0x00F0000; }
_foo:
.LBB_foo_0: ; entry
; IMPLICIT_DEF
oris r3, r3, 15
blr
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16826 91177308-0d34-0410-b5e6-96231b3b80d8
loading a 32bit constant into a register whose low halfword is all zeroes.
We now omit the ori after the lis for the following C code:
int bar(int y) { return y * 0x00F0000; }
_bar:
.LBB_bar_0: ; entry
; IMPLICIT_DEF
lis r2, 15
mullw r3, r3, r2
blr
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a map. This caused problems if a later object happened to be allocated at
the free'd object's address.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16813 91177308-0d34-0410-b5e6-96231b3b80d8
exponential behavior (bork!). This patch processes stuff with an
explicit SCC finder, allowing the algorithm to be more clear,
efficient, and also (as a bonus) correct! This gets us back to taking
0.6s to disassemble my horrible .bc file that previously took something
> 30 mins.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16811 91177308-0d34-0410-b5e6-96231b3b80d8
* Instead of handling dead functions specially, just nuke them.
* Be more aggressive about cleaning up after constification, in
particular, handle getelementptr instructions and constantexprs.
* Be a little bit more structured about how we process globals.
*** Delete globals that are only stored to, and never read. These are
clearly not useful, so they should go. This implements deadglobal.llx
This last one triggers quite a few times. In particular, 2208 in the
external tests, 1865 of which are in 252.eon. This shrinks eon from
1995094 to 1732341 bytes of bytecode.
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simplifications of the resultant program to avoid making later passes
do it all.
This allows us to constify globals that just have the same constant that
they are initialized stored into them.
Suprisingly this comes up ALL of the freaking time, dozens of times in
SPEC, 30 times in vortex alone.
For example, on 256.bzip2, it allows us to constify these two globals:
%smallMode = internal global ubyte 0 ; <ubyte*> [#uses=8]
%verbosity = internal global int 0 ; <int*> [#uses=49]
Which (with later optimizations) results in the bytecode file shrinking
from 82286 to 69686 bytes! Lets hear it for IPO :)
For the record, it's nuking lots of "if (verbosity > 2) { do lots of stuff }"
code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16793 91177308-0d34-0410-b5e6-96231b3b80d8
(PromoteAbstractToConcrete), and to use a set to avoid recomputation.
In particular, this set eliminates the potentially exponential cases
from this little recursive algorithm.
On a particularly nasty testcase, llvm-dis on the .bc file went from 34
minutes (which is when I killed it, it still hadn't finished) to 0.57s.
Remember kids, exponential algorithms are bad.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16772 91177308-0d34-0410-b5e6-96231b3b80d8
t:
mov %EDX, DWORD PTR [%ESP + 4]
mov %ECX, 2
mov %EAX, %EDX
sar %EDX, 31
idiv %ECX
mov %EAX, %EDX
ret
Generate:
t:
mov %ECX, DWORD PTR [%ESP + 4]
*** mov %EAX, %ECX
cdq
and %ECX, 1
xor %ECX, %EDX
sub %ECX, %EDX
*** mov %EAX, %ECX
ret
Note that the two marked moves are redundant, and should be eliminated by the
register allocator, but aren't.
Compare this to GCC, which generates:
t:
mov %eax, DWORD PTR [%esp+4]
mov %edx, %eax
shr %edx, 31
lea %ecx, [%edx+%eax]
and %ecx, -2
sub %eax, %ecx
ret
or ICC 8.0, which generates:
t:
movl 4(%esp), %ecx #3.5
movl $-2147483647, %eax #3.25
imull %ecx #3.25
movl %ecx, %eax #3.25
sarl $31, %eax #3.25
addl %ecx, %edx #3.25
subl %edx, %eax #3.25
addl %eax, %eax #3.25
negl %eax #3.25
subl %eax, %ecx #3.25
movl %ecx, %eax #3.25
ret #3.25
We would be in great shape if not for the moves.
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an instruction if it can be hoisted to a common dominator of the block.
This implements: test/Regression/Transforms/TailDup/MergeTest.ll
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