The Test instruction applied to the rCX register followed by a Jump if Zero
with an 8-bit displacement can be replaced by a single JCXZ/JECXZ/JRCXZ
instruction with no loss of performance (1 cycle + 1 cycle verses 2 cycles on
K8 processors) and a one or two byte decrease in I-cache use per instance.
Replacing TEST rCX/JZ sequences with the JrCXZ insn would be a good first step;
preferentially using the rCX register in order to maximize JrCXZ replacements
would be better.
--
Summary: TESTW{W,L,Q} rCX + JZ/JE should be replaced by
J{,E,R}CXZ when possible
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: nmiell at comcast dot net
GCC target triplet: i?86-*-*, x86_64-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29793
