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| author | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-08-19 00:30:17 +0000 |
|---|---|---|
| committer | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-08-19 00:30:17 +0000 |
| commit | 201f2463a72f88121a3a31e7386029e99d2d75da (patch) | |
| tree | 2de06ff5539d75a45c417bbcc27c888dcaf8bdae /lib | |
| parent | e6d5e88c1230eae7056a5cd6238e86c00cdff72f (diff) | |
Don't treat a partial <def,undef> operand as a read.
Normally, a partial register def is treated as reading the
super-register unless it also defines the full register like this:
%vreg110:sub_32bit<def> = COPY %vreg77:sub_32bit, %vreg110<imp-def>
This patch also uses the <undef> flag on partial defs to recognize
non-reading operands:
%vreg110:sub_32bit<def,undef> = COPY %vreg77:sub_32bit
This fixes a subtle bug in RegisterCoalescer where LIS->shrinkToUses
would treat a coalesced copy as still reading the register, extending
the live range artificially.
My test case only works when I disable DCE so a dead copy is left for
RegisterCoalescer, so I am not including it.
<rdar://problem/9967101>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138018 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/MachineInstr.cpp | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp index 97fe6f4893..11ecc84ded 100644 --- a/lib/CodeGen/MachineInstr.cpp +++ b/lib/CodeGen/MachineInstr.cpp @@ -901,7 +901,8 @@ MachineInstr::readsWritesVirtualRegister(unsigned Reg, Ops->push_back(i); if (MO.isUse()) Use |= !MO.isUndef(); - else if (MO.getSubReg()) + else if (MO.getSubReg() && !MO.isUndef()) + // A partial <def,undef> doesn't count as reading the register. PartDef = true; else FullDef = true; |