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The current Intel Atom microarchitecture has a feature whereby
when a function returns early then it is slightly faster to execute
a sequence of NOP instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction until
the return address is ready.
When compiling for X86 Atom only, this patch will run a pass,
called "X86PadShortFunction" which will add NOP instructions where less
than four cycles elapse between function entry and return.
It includes tests.
This patch has been updated to address Nadav's review comments
- Optimize only at >= O1 and don't do optimization if -Os is set
- Stores MachineBasicBlock* instead of BBNum
- Uses DenseMap instead of std::map
- Fixes placement of braces
Patch by Andy Zhang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171879 91177308-0d34-0410-b5e6-96231b3b80d8
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URL: http://llvm.org/viewvc/llvm-project?rev=171524&view=rev
Log:
The current Intel Atom microarchitecture has a feature whereby when a function
returns early then it is slightly faster to execute a sequence of NOP
instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction
until the return address is ready.
When compiling for X86 Atom only, this patch will run a pass, called
"X86PadShortFunction" which will add NOP instructions where less than four
cycles elapse between function entry and return.
It includes tests.
Patch by Andy Zhang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171603 91177308-0d34-0410-b5e6-96231b3b80d8
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returns early then it is slightly faster to execute a sequence of NOP
instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction
until the return address is ready.
When compiling for X86 Atom only, this patch will run a pass, called
"X86PadShortFunction" which will add NOP instructions where less than four
cycles elapse between function entry and return.
It includes tests.
Patch by Andy Zhang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171524 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165871 91177308-0d34-0410-b5e6-96231b3b80d8
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same width.
X86 doesn't have i8 cmovs so isel would emit a branch. Emitting branches at this
level is often not a good idea because it's too late for many optimizations to
kick in. This solution doesn't add any extensions (truncs are free) and tries
to avoid introducing partial register stalls by filtering direct copyfromregs.
I'm seeing a ~10% speedup on reading a random .png file with libpng15 via
graphicsmagick on x86_64/westmere, but YMMV depending on the microarchitecture.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165868 91177308-0d34-0410-b5e6-96231b3b80d8
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TwoAddressInstructionPass.
The generated code for Atom has a different code sequence. This is realted
to commit r160749.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160755 91177308-0d34-0410-b5e6-96231b3b80d8
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It is redundant; RegisterCoalescer will do the remat if it can't eliminate
the copy. Collected instruction counts before and after this. A few extra
instructions are generated due to spilling but it is normal to see these kinds
of changes with almost any small codegen change, according to Jakob.
This also fixed rdar://11830760 where xor is expected instead of movi0.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160749 91177308-0d34-0410-b5e6-96231b3b80d8
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This patch will optimize -(x != 0) on X86
FROM
cmpl $0x01,%edi
sbbl %eax,%eax
notl %eax
TO
negl %edi
sbbl %eax %eax
In order to generate negl, I added patterns in Target/X86/X86InstrCompiler.td:
def : Pat<(X86sub_flag 0, GR32:$src), (NEG32r GR32:$src)>;
rdar: 10961709
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156312 91177308-0d34-0410-b5e6-96231b3b80d8
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The commit is intended to fix rdar://10961709.
But it is the root cause of PR12720.
Revert it for now.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155992 91177308-0d34-0410-b5e6-96231b3b80d8
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This patch will optimize -(x != 0) on X86
FROM
cmpl $0x01,%edi
sbbl %eax,%eax
notl %eax
TO
negl %edi
sbbl %eax %eax
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155853 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155840 91177308-0d34-0410-b5e6-96231b3b80d8
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This is mostly to test the waters. I'd like to get results from FNT
build bots and other bots running on non-x86 platforms.
This feature has been pretty heavily tested over the last few months by
me, and it fixes several of the execution time regressions caused by the
inlining work by preventing inlining decisions from radically impacting
block layout.
I've seen very large improvements in yacr2 and ackermann benchmarks,
along with the expected noise across all of the benchmark suite whenever
code layout changes. I've analyzed all of the regressions and fixed
them, or found them to be impossible to fix. See my email to llvmdev for
more details.
I'd like for this to be in 3.1 as it complements the inliner changes,
but if any failures are showing up or anyone has concerns, it is just
a flag flip and so can be easily turned off.
I'm switching it on tonight to try and get at least one run through
various folks' performance suites in case SPEC or something else has
serious issues with it. I'll watch bots and revert if anything shows up.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154816 91177308-0d34-0410-b5e6-96231b3b80d8
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(movzx/movsx) because they give more information. Revert that part of the patch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129498 91177308-0d34-0410-b5e6-96231b3b80d8
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cases, it's much nicer and more informative reading the alias.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129497 91177308-0d34-0410-b5e6-96231b3b80d8
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int test(unsigned long a, unsigned long b) { return -(a < b); }
compiles to
_test: ## @test
cmpq %rsi, %rdi ## encoding: [0x48,0x39,0xf7]
sbbl %eax, %eax ## encoding: [0x19,0xc0]
ret ## encoding: [0xc3]
instead of
_test: ## @test
xorl %ecx, %ecx ## encoding: [0x31,0xc9]
cmpq %rsi, %rdi ## encoding: [0x48,0x39,0xf7]
movl $-1, %eax ## encoding: [0xb8,0xff,0xff,0xff,0xff]
cmovael %ecx, %eax ## encoding: [0x0f,0x43,0xc1]
ret ## encoding: [0xc3]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122451 91177308-0d34-0410-b5e6-96231b3b80d8
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result. This allows us to compile:
void *test12(long count) {
return new int[count];
}
into:
test12:
movl $4, %ecx
movq %rdi, %rax
mulq %rcx
movq $-1, %rdi
cmovnoq %rax, %rdi
jmp __Znam ## TAILCALL
instead of:
test12:
movl $4, %ecx
movq %rdi, %rax
mulq %rcx
seto %cl
testb %cl, %cl
movq $-1, %rdi
cmoveq %rax, %rdi
jmp __Znam
Of course it would be even better if the regalloc inverted the cmov to 'cmovoq',
which would eliminate the need for the 'movq %rdi, %rax'.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120936 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120933 91177308-0d34-0410-b5e6-96231b3b80d8
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select, inserting a not to compensate. Add a missing isZero check
that I lost somehow.
This improves codegen of:
void *func(long count) {
return new int[count];
}
from:
__Z4funcl: ## @_Z4funcl
movl $4, %ecx ## encoding: [0xb9,0x04,0x00,0x00,0x00]
movq %rdi, %rax ## encoding: [0x48,0x89,0xf8]
mulq %rcx ## encoding: [0x48,0xf7,0xe1]
testq %rdx, %rdx ## encoding: [0x48,0x85,0xd2]
movq $-1, %rdi ## encoding: [0x48,0xc7,0xc7,0xff,0xff,0xff,0xff]
cmoveq %rax, %rdi ## encoding: [0x48,0x0f,0x44,0xf8]
jmp __Znam ## TAILCALL
## encoding: [0xeb,A]
to:
__Z4funcl: ## @_Z4funcl
movl $4, %ecx ## encoding: [0xb9,0x04,0x00,0x00,0x00]
movq %rdi, %rax ## encoding: [0x48,0x89,0xf8]
mulq %rcx ## encoding: [0x48,0xf7,0xe1]
cmpq $1, %rdx ## encoding: [0x48,0x83,0xfa,0x01]
sbbq %rdi, %rdi ## encoding: [0x48,0x19,0xff]
notq %rdi ## encoding: [0x48,0xf7,0xd7]
orq %rax, %rdi ## encoding: [0x48,0x09,0xc7]
jmp __Znam ## TAILCALL
## encoding: [0xeb,A]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120932 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120930 91177308-0d34-0410-b5e6-96231b3b80d8
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1. generalize
(select (x == 0), -1, 0) -> (sign_bit (x - 1))
to:
(select (x == 0), -1, y) -> (sign_bit (x - 1)) | y
2. Handle the identical pattern that happens with !=:
(select (x != 0), y, -1) -> (sign_bit (x - 1)) | y
cmov is often high latency and can't fold immediates or
memory operands. For example for (x == 0) ? -1 : 1, before
we got:
< testb %sil, %sil
< movl $-1, %ecx
< movl $1, %eax
< cmovel %ecx, %eax
now we get:
> cmpb $1, %sil
> sbbl %eax, %eax
> orl $1, %eax
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120929 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120928 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120927 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120926 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81290 91177308-0d34-0410-b5e6-96231b3b80d8
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this is now the default.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49667 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49391 91177308-0d34-0410-b5e6-96231b3b80d8
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that need it (usually, grepping for some string
found in unwind info)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49364 91177308-0d34-0410-b5e6-96231b3b80d8
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EH info for these functions causes the tests to fail for
random reasons (e.g. looking for 'or' or counting lines
with asm-printer; labels count as lines.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49003 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42775 91177308-0d34-0410-b5e6-96231b3b80d8
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Remove && from the end of the lines to prevent tests from throwing run
lines into the background. Also, clean up places where the same command
is run multiple times by using a temporary file.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36142 91177308-0d34-0410-b5e6-96231b3b80d8
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Update these tests to not use the same name even though the type of the
value differs. After PR411 hits, type planes will be gone and it will be
illegal for a name to be used twice, regardless of type.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33660 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32115 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30120 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12585 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12559 91177308-0d34-0410-b5e6-96231b3b80d8
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12552 91177308-0d34-0410-b5e6-96231b3b80d8
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