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[ARM] Add <saturate> operand to SQRSHRL and UQRSHLL

Authored by miyuki on Jul 19 2019, 2:46 AM.

Description

[ARM] Add <saturate> operand to SQRSHRL and UQRSHLL

Summary:
According to the new Armv8-M specification
https://static.docs.arm.com/ddi0553/bh/DDI0553B_h_armv8m_arm.pdf the
instructions SQRSHRL and UQRSHLL now have an additional immediate
operand <saturate>. The new assembly syntax is:

SQRSHRL<c> RdaLo, RdaHi, #<saturate>, Rm
UQRSHLL<c> RdaLo, RdaHi, #<saturate>, Rm

where <saturate> can be either 64 (the existing behavior) or 48, in
that case the result is saturated to 48 bits.

The new operand is encoded as follows:

#64 Encoded as sat = 0
#48 Encoded as sat = 1

sat is bit 7 of the instruction bit pattern.

This patch adds a new assembler operand class MveSaturateOperand which
implements parsing and encoding. Decoding is implemented in
DecodeMVEOverlappingLongShift.

Reviewers: ostannard, simon_tatham, t.p.northover, samparker, dmgreen, SjoerdMeijer

Reviewed By: simon_tatham

Subscribers: javed.absar, kristof.beyls, hiraditya, pbarrio, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64810

llvm-svn: 366555

Details

Committed
miyukiJul 19 2019, 2:46 AM
Reviewer
simon_tatham
Differential Revision
D64810: [ARM] Add <saturate> operand to SQRSHRL and UQRSHLL
Parents
rG9c377105da0b: Revert r366458, r366467 and r366468
Branches
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Tags
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