Commit Graph

6 Commits

Author SHA1 Message Date
Benjamin Kramer ef6494f24d PR13578: Teach MachineCSE that instructions that use a constant register can be CSE'd safely.
This is common e.g. when doing rip-relative addressing on x86_64.

llvm-svn: 161728
2012-08-11 19:05:13 +00:00
Manman Ren cb36b8c2e6 MachineCSE: Update the heuristics for isProfitableToCSE.
If the result of a common subexpression is used at all uses of the candidate
expression, CSE should not increase the live range of the common subexpression.

rdar://11393714 and rdar://11819721

llvm-svn: 161396
2012-08-07 06:16:46 +00:00
Evan Cheng 0be4144a68 Allow machine-cse to look across MBB boundary when cse'ing instructions that
define physical registers. It's currently very restrictive, only catching
cases where the CE is in an immediate (and only) predecessor. But it catches
a surprising large number of cases.

rdar://10660865

llvm-svn: 147827
2012-01-10 02:02:58 +00:00
Evan Cheng c5c2cfa381 sext(undef) = 0, because the top bits will all be the same.
zext(undef) = 0, because the top bits will be zero.

llvm-svn: 127649
2011-03-15 02:22:10 +00:00
Evan Cheng b7ff5a0f20 Teach machine cse to commute instructions.
llvm-svn: 121903
2010-12-15 22:16:21 +00:00
Evan Cheng 80ad113731 Enable machine cse pass.
llvm-svn: 98132
2010-03-10 03:07:41 +00:00