Change the REG_SEQUENCE SDNode to take an explict register class ID as its first operand. This operand is lowered away by the time we reach MachineInstrs, so the actual register-allocation handling of them doesn't need to change.

This is intended to support using REG_SEQUENCE SDNode's with type MVT::untyped, and is part of the long road to eliminating some of the hacks we currently use to support register pairs and other strange constraints, particularly on ARM NEON.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133178 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/include/llvm/Target/TargetOpcodes.h b/include/llvm/Target/TargetOpcodes.h
index 01fba6628e..37f7b2fb8d 100644
--- a/include/llvm/Target/TargetOpcodes.h
+++ b/include/llvm/Target/TargetOpcodes.h
@@ -71,6 +71,10 @@ namespace TargetOpcode {
     /// REG_SEQUENCE - This variadic instruction is used to form a register that
     /// represent a consecutive sequence of sub-registers. It's used as register
     /// coalescing / allocation aid and must be eliminated before code emission.
+    // In SDNode form, the first operand encodes the register class created by
+    // the REG_SEQUENCE, while each subsequent pair names a vreg + subreg index
+    // pair.  Once it has been lowered to a MachineInstr, the regclass operand
+    // is no longer present.
     /// e.g. v1027 = REG_SEQUENCE v1024, 3, v1025, 4, v1026, 5
     /// After register coalescing references of v1024 should be replace with
     /// v1027:3, v1025 with v1027:4, etc.