mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-12-23 20:15:35 +00:00
303 lines
8.9 KiB
Plaintext
303 lines
8.9 KiB
Plaintext
Target Independent Opportunities:
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
We should make the following changes to clean up MachineInstr:
|
|
|
|
1. Add an Opcode field to TargetInstrDescriptor, so you can tell the opcode of
|
|
an instruction with just a TargetInstrDescriptor*.
|
|
2. Remove the Opcode field from MachineInstr, replacing it with a
|
|
TargetInstrDescriptor*.
|
|
3. Getting information about a machine instr then becomes:
|
|
MI->getInfo()->isTwoAddress()
|
|
instead of:
|
|
const TargetInstrInfo &TII = ...
|
|
TII.isTwoAddrInstr(MI->getOpcode())
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
FreeBench/mason contains code like this:
|
|
|
|
static p_type m0u(p_type p) {
|
|
int m[]={0, 8, 1, 2, 16, 5, 13, 7, 14, 9, 3, 4, 11, 12, 15, 10, 17, 6};
|
|
p_type pu;
|
|
pu.a = m[p.a];
|
|
pu.b = m[p.b];
|
|
pu.c = m[p.c];
|
|
return pu;
|
|
}
|
|
|
|
We currently compile this into a memcpy from a static array into 'm', then
|
|
a bunch of loads from m. It would be better to avoid the memcpy and just do
|
|
loads from the static array.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Make the PPC branch selector target independant
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Get the C front-end to expand hypot(x,y) -> llvm.sqrt(x*x+y*y) when errno and
|
|
precision don't matter (ffastmath). Misc/mandel will like this. :)
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Solve this DAG isel folding deficiency:
|
|
|
|
int X, Y;
|
|
|
|
void fn1(void)
|
|
{
|
|
X = X | (Y << 3);
|
|
}
|
|
|
|
compiles to
|
|
|
|
fn1:
|
|
movl Y, %eax
|
|
shll $3, %eax
|
|
orl X, %eax
|
|
movl %eax, X
|
|
ret
|
|
|
|
The problem is the store's chain operand is not the load X but rather
|
|
a TokenFactor of the load X and load Y, which prevents the folding.
|
|
|
|
There are two ways to fix this:
|
|
|
|
1. The dag combiner can start using alias analysis to realize that y/x
|
|
don't alias, making the store to X not dependent on the load from Y.
|
|
2. The generated isel could be made smarter in the case it can't
|
|
disambiguate the pointers.
|
|
|
|
Number 1 is the preferred solution.
|
|
|
|
This has been "fixed" by a TableGen hack. But that is a short term workaround
|
|
which will be removed once the proper fix is made.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
On targets with expensive 64-bit multiply, we could LSR this:
|
|
|
|
for (i = ...; ++i) {
|
|
x = 1ULL << i;
|
|
|
|
into:
|
|
long long tmp = 1;
|
|
for (i = ...; ++i, tmp+=tmp)
|
|
x = tmp;
|
|
|
|
This would be a win on ppc32, but not x86 or ppc64.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Shrink: (setlt (loadi32 P), 0) -> (setlt (loadi8 Phi), 0)
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Reassociate should turn: X*X*X*X -> t=(X*X) (t*t) to eliminate a multiply.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Interesting? testcase for add/shift/mul reassoc:
|
|
|
|
int bar(int x, int y) {
|
|
return x*x*x+y+x*x*x*x*x*y*y*y*y;
|
|
}
|
|
int foo(int z, int n) {
|
|
return bar(z, n) + bar(2*z, 2*n);
|
|
}
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
These two functions should generate the same code on big-endian systems:
|
|
|
|
int g(int *j,int *l) { return memcmp(j,l,4); }
|
|
int h(int *j, int *l) { return *j - *l; }
|
|
|
|
this could be done in SelectionDAGISel.cpp, along with other special cases,
|
|
for 1,2,4,8 bytes.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
This code:
|
|
int rot(unsigned char b) { int a = ((b>>1) ^ (b<<7)) & 0xff; return a; }
|
|
|
|
Can be improved in two ways:
|
|
|
|
1. The instcombiner should eliminate the type conversions.
|
|
2. The X86 backend should turn this into a rotate by one bit.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Add LSR exit value substitution. It'll probably be a win for Ackermann, etc.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
It would be nice to revert this patch:
|
|
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20060213/031986.html
|
|
|
|
And teach the dag combiner enough to simplify the code expanded before
|
|
legalize. It seems plausible that this knowledge would let it simplify other
|
|
stuff too.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
For packed types, TargetData.cpp::getTypeInfo() returns alignment that is equal
|
|
to the type size. It works but can be overly conservative as the alignment of
|
|
specific packed types are target dependent.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
We should add 'unaligned load/store' nodes, and produce them from code like
|
|
this:
|
|
|
|
v4sf example(float *P) {
|
|
return (v4sf){P[0], P[1], P[2], P[3] };
|
|
}
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
We should constant fold packed type casts at the LLVM level, regardless of the
|
|
cast. Currently we cannot fold some casts because we don't have TargetData
|
|
information in the constant folder, so we don't know the endianness of the
|
|
target!
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Add support for conditional increments, and other related patterns. Instead
|
|
of:
|
|
|
|
movl 136(%esp), %eax
|
|
cmpl $0, %eax
|
|
je LBB16_2 #cond_next
|
|
LBB16_1: #cond_true
|
|
incl _foo
|
|
LBB16_2: #cond_next
|
|
|
|
emit:
|
|
movl _foo, %eax
|
|
cmpl $1, %edi
|
|
sbbl $-1, %eax
|
|
movl %eax, _foo
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Combine: a = sin(x), b = cos(x) into a,b = sincos(x).
|
|
|
|
Expand these to calls of sin/cos and stores:
|
|
double sincos(double x, double *sin, double *cos);
|
|
float sincosf(float x, float *sin, float *cos);
|
|
long double sincosl(long double x, long double *sin, long double *cos);
|
|
|
|
Doing so could allow SROA of the destination pointers. See also:
|
|
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17687
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Scalar Repl cannot currently promote this testcase to 'ret long cst':
|
|
|
|
%struct.X = type { int, int }
|
|
%struct.Y = type { %struct.X }
|
|
ulong %bar() {
|
|
%retval = alloca %struct.Y, align 8 ; <%struct.Y*> [#uses=3]
|
|
%tmp12 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 0
|
|
store int 0, int* %tmp12
|
|
%tmp15 = getelementptr %struct.Y* %retval, int 0, uint 0, uint 1
|
|
store int 1, int* %tmp15
|
|
%retval = cast %struct.Y* %retval to ulong*
|
|
%retval = load ulong* %retval ; <ulong> [#uses=1]
|
|
ret ulong %retval
|
|
}
|
|
|
|
it should be extended to do so.
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Turn this into a single byte store with no load (the other 3 bytes are
|
|
unmodified):
|
|
|
|
void %test(uint* %P) {
|
|
%tmp = load uint* %P
|
|
%tmp14 = or uint %tmp, 3305111552
|
|
%tmp15 = and uint %tmp14, 3321888767
|
|
store uint %tmp15, uint* %P
|
|
ret void
|
|
}
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
dag/inst combine "clz(x)>>5 -> x==0" for 32-bit x.
|
|
|
|
Compile:
|
|
|
|
int bar(int x)
|
|
{
|
|
int t = __builtin_clz(x);
|
|
return -(t>>5);
|
|
}
|
|
|
|
to:
|
|
|
|
_bar: addic r3,r3,-1
|
|
subfe r3,r3,r3
|
|
blr
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
Legalize should lower ctlz like this:
|
|
ctlz(x) = popcnt((x-1) & ~x)
|
|
|
|
on targets that have popcnt but not ctlz. itanium, what else?
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
quantum_sigma_x in 462.libquantum contains the following loop:
|
|
|
|
for(i=0; i<reg->size; i++)
|
|
{
|
|
/* Flip the target bit of each basis state */
|
|
reg->node[i].state ^= ((MAX_UNSIGNED) 1 << target);
|
|
}
|
|
|
|
Where MAX_UNSIGNED/state is a 64-bit int. On a 32-bit platform it would be just
|
|
so cool to turn it into something like:
|
|
|
|
long long Res = ((MAX_UNSIGNED) 1 << target);
|
|
if (target < 32) {
|
|
for(i=0; i<reg->size; i++)
|
|
reg->node[i].state ^= Res & 0xFFFFFFFFULL;
|
|
} else {
|
|
for(i=0; i<reg->size; i++)
|
|
reg->node[i].state ^= Res & 0xFFFFFFFF00000000ULL
|
|
}
|
|
|
|
... which would only do one 32-bit XOR per loop iteration instead of two.
|
|
|
|
It would also be nice to recognize the reg->size doesn't alias reg->node[i], but
|
|
alas...
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
This isn't recognized as bswap by instcombine:
|
|
|
|
unsigned int swap_32(unsigned int v) {
|
|
v = ((v & 0x00ff00ffU) << 8) | ((v & 0xff00ff00U) >> 8);
|
|
v = ((v & 0x0000ffffU) << 16) | ((v & 0xffff0000U) >> 16);
|
|
return v;
|
|
}
|
|
|
|
//===---------------------------------------------------------------------===//
|
|
|
|
These should turn into single 16-bit (unaligned?) loads on little/big endian
|
|
processors.
|
|
|
|
unsigned short read_16_le(const unsigned char *adr) {
|
|
return adr[0] | (adr[1] << 8);
|
|
}
|
|
unsigned short read_16_be(const unsigned char *adr) {
|
|
return (adr[0] << 8) | adr[1];
|
|
}
|
|
|
|
//===---------------------------------------------------------------------===//
|