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[PowerPC][Future] Branch Distance Estimation For Prefixed Instructions

Authored by stefanp on Jan 30 2020, 6:35 AM.

Description

[PowerPC][Future] Branch Distance Estimation For Prefixed Instructions

By adding the prefixed instructions the branch distances are no longer
computed correctly. Since prefixed instructions cannot cross a 64 byte
boundary we have to assume that a prefixed instruction may have a nop
prepended to it. This patch tries to take that nop into consideration
when computing the size of basic blocks.

Differential Revision: https://reviews.llvm.org/D72572