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* Disabled subregister copy coalescing during MachineCSE.Andrew Trick2013-12-171-0/+1
| | | | | | | | | This effectively backs out r197465 but leaves some of the general fixes in place. Not all targets are ready to handle this feature. To enable it, some infrastructure work is needed to better handle register class constraints. llvm-svn: 197514
* Allow MachineCSE to coalesce trivial subregister copies the same way that it ↵Andrew Trick2013-12-171-0/+42
| | | | | | | | | | | | | | | | | | | | coalesces normal copies. Without this, MachineCSE is powerless to handle redundant operations with truncated source operands. This required fixing the 2-addr pass to handle tied subregisters. It isn't clear what combinations of subregisters can legally be tied, but the simple case of truncated source operands is now safely handled: %vreg11<def> = COPY %vreg1:sub_32bit; GR32:%vreg11 GR64:%vreg1 %vreg12<def> = COPY %vreg2:sub_32bit; GR32:%vreg12 GR64:%vreg2 %vreg13<def,tied1> = ADD32rr %vreg11<tied0>, %vreg12<kill>, %EFLAGS<imp-def> Test case: cse-add-with-overflow.ll. This exposed an existing bug in PPCInstrInfo::commuteInstruction. Thanks to Rafael for the test case: PowerPC/crash.ll. llvm-svn: 197465
* Revert "Allow MachineCSE to coalesce trivial subregister copies the same way ↵Rafael Espindola2013-12-161-42/+0
| | | | | | | | | | that it coalesces normal copies." This reverts commit r197414. It broke the ppc64 bootstrap. I will post a testcase in a sec. llvm-svn: 197424
* Allow MachineCSE to coalesce trivial subregister copies the same wayAndrew Trick2013-12-161-0/+42
that it coalesces normal copies. Without this, MachineCSE is powerless to handle redundant operations with truncated source operands. This required fixing the 2-addr pass to handle tied subregisters. It isn't clear what combinations of subregisters can legally be tied, but the simple case of truncated source operands is now safely handled: %vreg11<def> = COPY %vreg1:sub_32bit; GR32:%vreg11 GR64:%vreg1 %vreg12<def> = COPY %vreg2:sub_32bit; GR32:%vreg12 GR64:%vreg2 %vreg13<def,tied1> = ADD32rr %vreg11<tied0>, %vreg12<kill>, %EFLAGS<imp-def> llvm-svn: 197414
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