This patch fixes a very subtle bug in regmask calculation. Thanks to zan
jyu Wong <zyfwong@gmail.com> for bringing this to notice.
For example if CL is only clobbered than CH should not be marked
clobbered but CX, RCX and ECX should be mark clobbered. Previously for
each modified register all of its aliases are marked clobbered by
markRegClobbred() in RegUsageInfoCollector.cpp but that is wrong because
when CL is clobbered then MRI::isPhysRegModified() will return true for
CL, CX, ECX, RCX which is correct behavior but then for CX, EXC, RCX we
mark CH also clobbered as CH is aliased to CX,ECX,RCX so
markRegClobbred() is not required because isPhysRegModified already take
cares of proper aliasing register. A very simple test case has been
added to verify this change.
Please find relevant bug report here :
http://llvm.org/PR28567
Patch by Vivek Pandya <vivekvpandya@gmail.com>
Differential Revision: https://reviews.llvm.org/D22400
llvm-svn: 276235
IPRA try to optimize caller saved register by propagating register
usage information from callee to caller so it is beneficial to have
caller saved registers compare to callee saved registers when IPRA
is enabled. Please find more detailed explanation here
https://groups.google.com/d/msg/llvm-dev/XRzGhJ9wtZg/tjAJqb0eEgAJ.
This change makes local function do not have any callee preserved
register when IPRA is enabled. A simple test case is also added to
verify this change.
Patch by Vivek Pandya <vivekvpandya@gmail.com>
Differential Revision: http://reviews.llvm.org/D21561
llvm-svn: 275347
Add an option to enable the analysis of MachineFunction register
usage to extract the list of clobbered registers.
When enabled, the CodeGen order is changed to be bottom up on the Call
Graph.
The analysis is split in two parts, RegUsageInfoCollector is the
MachineFunction Pass that runs post-RA and collect the list of
clobbered registers to produce a register mask.
An immutable pass, RegisterUsageInfo, stores the RegMask produced by
RegUsageInfoCollector, and keep them available. A future tranformation
pass will use this information to update every call-sites after
instruction selection.
Patch by Vivek Pandya <vivekvpandya@gmail.com>
Differential Revision: http://reviews.llvm.org/D20769
llvm-svn: 272403
Mehdi Amini