Function pointers under PPC64 ELFv1 (which is used on PPC64/Linux on the
POWER7, A2 and earlier cores) are really pointers to a function descriptor, a
structure with three pointers: the actual pointer to the code to which to jump,
the pointer to the TOC needed by the callee, and an environment pointer. We
used to chain these loads, and make them opaque to the rest of the optimizer,
so that they'd always occur directly before the call. This is not necessary,
and in fact, highly suboptimal on embedded cores. Once the function pointer is
known, the loads can be performed ahead of time; in fact, they can be hoisted
out of loops.
Now these function descriptors are almost always generated by the linker, and
thus the contents of the descriptors are invariant. As a result, by default,
we'll mark the associated loads as invariant (allowing them to be hoisted out
of loops). I've added a target feature to turn this off, however, just in case
someone needs that option (constructing an on-stack descriptor, casting it to a
function pointer, and then calling it cannot be well-defined C/C++ code, but I
can imagine some JIT-compilation system doing so).
Consider this simple test:
$ cat call.c
typedef void (*fp)();
void bar(fp x) {
for (int i = 0; i < 1600000000; ++i)
x();
}
$ cat main.c
typedef void (*fp)();
void bar(fp x);
void foo() {}
int main() {
bar(foo);
}
On the PPC A2 (the BG/Q supercomputer), marking the function-descriptor loads
as invariant brings the execution time down to ~8 seconds from ~32 seconds with
the loads in the loop.
The difference on the POWER7 is smaller. Compiling with:
gcc -std=c99 -O3 -mcpu=native call.c main.c : ~6 seconds [this is 4.8.2]
clang -O3 -mcpu=native call.c main.c : ~5.3 seconds
clang -O3 -mcpu=native call.c main.c -mno-invariant-function-descriptors : ~4 seconds
(looks like we'd benefit from additional loop unrolling here, as a first
guess, because this is faster with the extra loads)
The -mno-invariant-function-descriptors will be added to Clang shortly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226207 91177308-0d34-0410-b5e6-96231b3b80d8
IRCE eliminates range checks of the form
0 <= A * I + B < Length
by splitting a loop's iteration space into three segments in a way
that the check is completely redundant in the middle segment. As an
example, IRCE will convert
len = < known positive >
for (i = 0; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
to
len = < known positive >
limit = smin(n, len)
// no first segment
for (i = 0; i < limit; i++) {
if (0 <= i && i < len) { // this check is fully redundant
do_something();
} else {
throw_out_of_bounds();
}
}
for (i = limit; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
IRCE can deal with multiple range checks in the same loop (it takes
the intersection of the ranges that will make each of them redundant
individually).
Currently IRCE does not do any profitability analysis. That is a
TODO.
Please note that the status of this pass is *experimental*, and it is
not part of any default pass pipeline. Having said that, I will love
to get feedback and general input from people interested in trying
this out.
Differential Revision: http://reviews.llvm.org/D6693
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226201 91177308-0d34-0410-b5e6-96231b3b80d8
Reapply r226071 with fixes. Two fixes:
1. We need to manually remove the old and create the new 'deaf defs'
associated with physical register definitions when we move the definition of
the physical register from the copy point to the point of the original vreg def.
This problem was picked up by the machinstr verifier, and could trigger a
verification failure on test/CodeGen/X86/2009-02-12-DebugInfoVLA.ll, so I've
turned on the verifier in the tests.
2. When moving the def point of the phys reg up, we need to make sure that it
is neither defined nor read in between the two instructions. We don't, however,
extend the live ranges of phys reg defs to cover uses, so just checking for
live-range overlap between the pair interval and the phys reg aliases won't
pick up reads. As a result, we manually iterate over the range and check for
reads.
A test soon to be committed to the PowerPC backend will test this change.
Original commit message:
[RegisterCoalescer] Remove copies to reserved registers
This allows the RegisterCoalescer to join "non-flipped" range pairs with a
physical destination register -- which allows the RegisterCoalescer to remove
copies like this:
<vreg> = something (maybe a load, for example)
... (things that don't use PHYSREG)
PHYSREG = COPY <vreg>
(with all of the restrictions normally applied by the RegisterCoalescer: having
compatible register classes, etc. )
Previously, the RegisterCoalescer handled only the opposite case (copying
*from* a physical register). I don't handle the problem fully here, but try to
get the common case where there is only one use of <vreg> (the COPY).
An upcoming commit to the PowerPC backend will make this pattern much more
common on PPC64/ELF systems.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226200 91177308-0d34-0410-b5e6-96231b3b80d8
Use static functions for helpers rather than static member functions. a) this changes the linking (minor at best), and b) this makes it obvious no object state is involved.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226198 91177308-0d34-0410-b5e6-96231b3b80d8
This removes some duplicated classes and definitions.
These instructions are defined:
_e32 // pseudo
_e32_si
_e64 // pseudo
_e64_si
_e64_vi
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226191 91177308-0d34-0410-b5e6-96231b3b80d8
v2: modify hasVALU32BitEncoding instead
v3: - add pseudoToMCOpcode helper to AMDGPUInstInfo, which is used by both
hasVALU32BitEncoding and AMDGPUMCInstLower::lower
- report an error if a pseudo can't be lowered
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226188 91177308-0d34-0410-b5e6-96231b3b80d8
Avoid using unions for storing the return value from
LLVMGetGlobalValueAddress() and LLVMGetFunctionAddress() and accessing it as
a pointer through another pointer member. This causes problems on 32-bit big
endian machines since the pointer gets the higher part of the return value of
the aforementioned functions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226170 91177308-0d34-0410-b5e6-96231b3b80d8
This patch was generated by a clang tidy checker that is being open sourced.
The documentation of that checker is the following:
/// The emptiness of a container should be checked using the empty method
/// instead of the size method. It is not guaranteed that size is a
/// constant-time function, and it is generally more efficient and also shows
/// clearer intent to use empty. Furthermore some containers may implement the
/// empty method but not implement the size method. Using empty whenever
/// possible makes it easier to switch to another container in the future.
Patch by Gábor Horváth!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226161 91177308-0d34-0410-b5e6-96231b3b80d8
TargetLibraryAnalysis pass.
There are actually no direct tests of this already in the tree. I've
added the most basic test that the pass manager bits themselves work,
and the TLI object produced will be tested by an upcoming patches as
they port passes which rely on TLI.
This is starting to point out the awkwardness of the invalidate API --
it seems poorly fitting on the *result* object. I suspect I will change
it to live on the analysis instead, but that's not for this change, and
I'd rather have a few more passes ported in order to have more
experience with how this plays out.
I believe there is only one more analysis required in order to start
porting instcombine. =]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226160 91177308-0d34-0410-b5e6-96231b3b80d8
The pass is really just a means of accessing a cached instance of the
TargetLibraryInfo object, and this way we can re-use that object for the
new pass manager as its result.
Lots of delta, but nothing interesting happening here. This is the
common pattern that is developing to allow analyses to live in both the
old and new pass manager -- a wrapper pass in the old pass manager
emulates the separation intrinsic to the new pass manager between the
result and pass for analyses.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226157 91177308-0d34-0410-b5e6-96231b3b80d8
Reverting this while I investigate some bad behavior this is causing. As a
possibly-related issue, adding -verify-machineinstrs to one of the test cases
now fails because of this change:
llc test/CodeGen/X86/2009-02-12-DebugInfoVLA.ll -march=x86-64 -o - -verify-machineinstrs
*** Bad machine code: No instruction at def index ***
- function: foo
- basic block: BB#0 return (0x10007e21f10) [0B;736B)
- liverange: [128r,128d:9)[160r,160d:8)[176r,176d:7)[336r,336d:6)[464r,464d:5)[480r,480d:4)[624r,624d:3)[752r,752d:2)[768r,768d:1)[78
4r,784d:0) 0@784r 1@768r 2@752r 3@624r 4@480r 5@464r 6@336r 7@176r 8@160r 9@128r
- register: %DS
Valno #3 is defined at 624r
*** Bad machine code: Live segment doesn't end at a valid instruction ***
- function: foo
- basic block: BB#0 return (0x10007e21f10) [0B;736B)
- liverange: [128r,128d:9)[160r,160d:8)[176r,176d:7)[336r,336d:6)[464r,464d:5)[480r,480d:4)[624r,624d:3)[752r,752d:2)[768r,768d:1)[78
4r,784d:0) 0@784r 1@768r 2@752r 3@624r 4@480r 5@464r 6@336r 7@176r 8@160r 9@128r
- register: %DS
[624r,624d:3)
LLVM ERROR: Found 2 machine code errors.
where 624r corresponds exactly to the interval combining change:
624B %RSP<def> = COPY %vreg16; GR64:%vreg16
Considering merging %vreg16 with %RSP
RHS = %vreg16 [608r,624r:0) 0@608r
updated: 608B %RSP<def> = MOV64rm <fi#3>, 1, %noreg, 0, %noreg; mem:LD8[%saved_stack.1]
Success: %vreg16 -> %RSP
Result = %RSP
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226086 91177308-0d34-0410-b5e6-96231b3b80d8
While the term "Target" is in the name, it doesn't really have to do
with the LLVM Target library -- this isn't an abstraction which LLVM
targets generally need to implement or extend. It has much more to do
with modeling the various runtime libraries on different OSes and with
different runtime environments. The "target" in this sense is the more
general sense of a target of cross compilation.
This is in preparation for porting this analysis to the new pass
manager.
No functionality changed, and updates inbound for Clang and Polly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226078 91177308-0d34-0410-b5e6-96231b3b80d8
The bug was introduced in r225282. r225282 assumed that sub X, Y is
the same as add X, -Y. This is not correct if we are going to upgrade
the sub to sub nuw. This change fixes the issue by making the
optimization ignore sub instructions.
Differential Revision: http://reviews.llvm.org/D6979
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226075 91177308-0d34-0410-b5e6-96231b3b80d8
This adds support for creating an InstAlias with a negative immediate, i.e.:
def NOT : InstAlias<"not $dst, $src", (XORI GR32:$dst, GR32:$src, -1)>;
by resolving this problem:
RISCVGenAsmMatcher.inc:95:11: error: expected '= constant-expression' or end of enumerator definition
CVT_imm_-1,
^^^^^^^^^^
Patch by Jordy Potman, thanks!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226073 91177308-0d34-0410-b5e6-96231b3b80d8
This allows the RegisterCoalescer to join "non-flipped" range pairs with a
physical destination register -- which allows the RegisterCoalescer to remove
copies like this:
<vreg> = something (maybe a load, for example)
... (things that don't use PHYSREG)
PHYSREG = COPY <vreg>
(with all of the restrictions normally applied by the RegisterCoalescer: having
compatible register classes, etc. )
Previously, the RegisterCoalescer handled only the opposite case (copying
*from* a physical register). I don't handle the problem fully here, but try to
get the common case where there is only one use of <vreg> (the COPY).
An upcoming commit to the PowerPC backend will make this pattern much more
common on PPC64/ELF systems.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226071 91177308-0d34-0410-b5e6-96231b3b80d8
Fill out our support for the floating-point status and control register
instructions (mcrfs and friends). As it turns out, these are necessary for
compiling src/test/harness_fp.h in TBB for PowerPC.
Thanks to Raf Schietekat for reporting the issue!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226070 91177308-0d34-0410-b5e6-96231b3b80d8
it's defined in the current module. Clang generates this situation for the
C++14 sized deallocation functions, because it generates a weak definition in
case one isn't provided by the C++ runtime library.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226069 91177308-0d34-0410-b5e6-96231b3b80d8
