Displaying 5 results from an estimated 5 matches for "vstore".
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2013 Jul 10
4
[LLVMdev] unaligned AVX store gets split into two instructions
...X.
3.3 is splitting up an unaligned vector load but in 3.2, it was emitted as
a single instruction (details below).
In a matrix-matrix inner-kernel, I see a ~25% decrease in performance,
which seems to be due to this.
Any ideas why this changed? Thanks!
Zach
LLVM Code:
define <4 x double> @vstore(<4 x double>*) {
entry:
%1 = load <4 x double>* %0, align 8
ret <4 x double> %1
}
------------------------------------------------------------
Running llvm-32/bin/llc vstore.ll creates:
.section __TEXT,__text,regular,pure_instructions
.globl _vstore
.align 4, 0x90
_vstore:...
2017 Jun 25
2
AVX Scheduling and Parallelism
...reuse of XMM0 and XMM1 across loop-unroll instances does not inhibit instruction-level parallelism.
Modern X86 processors use register renaming that can eliminate the dependencies in the instruction stream. In the example you provided, the processor should be able to identify the 2-vloads + vadd + vstore sequences as independent and pipeline their execution.
Thanks, Zvi
From: Hal Finkel [mailto:hfinkel at anl.gov]
Sent: Saturday, June 24, 2017 05:17
To: hameeza ahmed <hahmed2305 at gmail.com>; llvm-dev at lists.llvm.org
Cc: Demikhovsky, Elena <elena.demikhovsky at intel.com>; Rackover...
2017 Jun 25
0
AVX Scheduling and Parallelism
...ss loop-unroll instances does not inhibit
> instruction-level parallelism.
>
> Modern X86 processors use register renaming that can eliminate the
> dependencies in the instruction stream. In the example you provided,
> the processor should be able to identify the 2-vloads + vadd + vstore
> sequences as independent and pipeline their execution.
>
> Thanks, Zvi
>
> *From:*Hal Finkel [mailto:hfinkel at anl.gov]
> *Sent:* Saturday, June 24, 2017 05:17
> *To:* hameeza ahmed <hahmed2305 at gmail.com>; llvm-dev at lists.llvm.org
> *Cc:* Demikhovsky, Elena &l...
2017 Jun 24
4
AVX Scheduling and Parallelism
Hello,
After generating AVX code for large no of iterations i came to realize that
it still uses only 2 registers zmm0 and zmm1 when the loop urnroll
factor=1024,
i wonder if this register allocation allows operations in parallel?
Also i know all the elements within a single vector instruction are
computed in parallel but does the elements of multiple instructions
computed in parallel? like are
2020 Jun 26
2
How to implement load/store for vector predicate register
Hi,
I am planning to expanding the pseudo instructions in XXXTargetLowering::EmitInstrWithCustomInserter(), and use temporary virtual registers as operands.
If I use virtual registers, do I need to mark them as "early clobber"?
I saw that sometimes they marked virtual register as "early clobber" in EmitInstrWithCustomInserter() in MIPS backend.
What is the effect of marking a