[llvm-commits] [llvm] r141139 - /llvm/trunk/lib/CodeGen/VirtRegMap.cpp
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Oct 4 17:01:49 PDT 2011
Author: stoklund
Date: Tue Oct 4 19:01:48 2011
New Revision: 141139
URL: http://llvm.org/viewvc/llvm-project?rev=141139&view=rev
Log:
Also add <imp-use,kill> flags for redefined super-registers.
For example:
%vreg10:dsub_0<def,undef> = COPY %vreg1
%vreg10:dsub_1<def> = COPY %vreg2
is rewritten as:
%D2<def> = COPY %D0, %Q1<imp-def>
%D3<def> = COPY %D1, %Q1<imp-use,kill>, %Q1<imp-def>
The first COPY doesn't care about the previous value of %Q1, so it
doesn't read that register.
The second COPY is a partial redefinition of %Q1, so it implicitly kills
and redefines that register.
This makes it possible to recognize instructions that can harmlessly
clobber the full super-register. The write and don't read the
super-register.
Modified:
llvm/trunk/lib/CodeGen/VirtRegMap.cpp
Modified: llvm/trunk/lib/CodeGen/VirtRegMap.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/VirtRegMap.cpp?rev=141139&r1=141138&r2=141139&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/VirtRegMap.cpp (original)
+++ llvm/trunk/lib/CodeGen/VirtRegMap.cpp Tue Oct 4 19:01:48 2011
@@ -285,14 +285,24 @@
// Preserve semantics of sub-register operands.
if (MO.getSubReg()) {
// A virtual register kill refers to the whole register, so we may
- // have to add <imp-use,kill> operands for the super-register.
- if (MO.isUse()) {
- if (MO.isKill() && !MO.isUndef())
- SuperKills.push_back(PhysReg);
- } else if (MO.isDead())
- SuperDeads.push_back(PhysReg);
- else
- SuperDefs.push_back(PhysReg);
+ // have to add <imp-use,kill> operands for the super-register. A
+ // partial redef always kills and redefines the super-register.
+ if (MO.readsReg() && (MO.isDef() || MO.isKill()))
+ SuperKills.push_back(PhysReg);
+
+ if (MO.isDef()) {
+ // The <def,undef> flag only makes sense for sub-register defs, and
+ // we are substituting a full physreg. An <imp-use,kill> operand
+ // from the SuperKills list will represent the partial read of the
+ // super-register.
+ MO.setIsUndef(false);
+
+ // Also add implicit defs for the super-register.
+ if (MO.isDead())
+ SuperDeads.push_back(PhysReg);
+ else
+ SuperDefs.push_back(PhysReg);
+ }
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());
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