[llvm-commits] LLVM patch to support ARM fused multiply add/subtract instructions

[Ana Pazos]

Hello folks,

 

Some ARMv7-A processor implementations  (e.g, Qualcomm 8960, ARM Cortex-A5)
support fused multiply add/subtract instructions (VFMA/VFMS) which have
lower latency and greater accuracy than the chained multiply add/subtract
instructions (VMLA/VMLS).

 

I have modified LLVM ARM target files to add support for fused multiply
add/subtract instructions. A processor definition just needs to add
'FeatureNEONVFP4'  to its list of subtarget features in order to enable the
generation of fused multiply add/subtract instructions.

 

The patch is attached for your review, if you have interest in merging this
change into LLVM.

 

Patch details:

fusedMACpatch.diff

Changes to ARM-specific files to support fused multiply add/subtract
instructions.

Associated fused multiply add/subtract instructions with processor subtarget
feature 'FeatureNEONVFP4'  and with the assembler feature flag 'neon-vfpv4'
.

 

fusedMAC.ll

Test to check for generated fused multiply accumulate and subtract
instructions.

 

failures.txt

Failure report from running llvm/test and projects/test-suite on ARM.

 

Thank you,

Ana.

 

 

 

--

Qualcomm Innovation Center, Inc is a member of Code Aurora Forum

 

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