Add a pseudo instruction REG_SEQUENCE that takes a list of registers and
sub-register indices and outputs a single super register which is formed from
a consecutive sequence of registers.
This is used as register allocation / coalescing aid and it is useful to
represent instructions that output register pairs / quads. For example,
v1024, v1025 = vload <address>
where v1024 and v1025 forms a register pair.
This really should be modelled as
v1024<3>, v1025<4> = vload <address>
but it would violate SSA property before register allocation is done.
Currently we use insert_subreg to form the super register:
v1026 = implicit_def
v1027 - insert_subreg v1026, v1024, 3
v1028 = insert_subreg v1027, v1025, 4
...
= use v1024
= use v1028
But this adds pseudo live interval overlap between v1024 and v1025.
We can now modeled it as
v1024, v1025 = vload <address>
v1026 = REG_SEQUENCE v1024, 3, v1025, 4
...
= use v1024
= use v1026
After coalescing, it will be
v1026<3>, v1025<4> = vload <address>
...
= use v1026<3>
= use v1026
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102815 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/CodeGenTarget.cpp b/utils/TableGen/CodeGenTarget.cpp
index 0392895..1efe2ff 100644
--- a/utils/TableGen/CodeGenTarget.cpp
+++ b/utils/TableGen/CodeGenTarget.cpp
@@ -326,6 +326,7 @@
const CodeGenInstruction *COPY_TO_REGCLASS =
GetInstByName("COPY_TO_REGCLASS", Insts);
const CodeGenInstruction *DBG_VALUE = GetInstByName("DBG_VALUE", Insts);
+ const CodeGenInstruction *REG_SEQUENCE = GetInstByName("REG_SEQUENCE", Insts);
// Print out the rest of the instructions now.
InstrsByEnum.push_back(PHI);
@@ -340,6 +341,7 @@
InstrsByEnum.push_back(SUBREG_TO_REG);
InstrsByEnum.push_back(COPY_TO_REGCLASS);
InstrsByEnum.push_back(DBG_VALUE);
+ InstrsByEnum.push_back(REG_SEQUENCE);
unsigned EndOfPredefines = InstrsByEnum.size();
@@ -357,7 +359,8 @@
CGI != IMPLICIT_DEF &&
CGI != SUBREG_TO_REG &&
CGI != COPY_TO_REGCLASS &&
- CGI != DBG_VALUE)
+ CGI != DBG_VALUE &&
+ CGI != REG_SEQUENCE)
InstrsByEnum.push_back(CGI);
}