[llvm] [RISCV] RISC-V split register allocation and move vsetvl pass in between (PR #70549)

[Michael Maitland via llvm-commits]

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@@ -245,6 +250,74 @@ bool RISCVTargetMachine::isNoopAddrSpaceCast(unsigned SrcAS,
 }
 
 namespace {
+
+class RVVRegisterRegAlloc : public RegisterRegAllocBase<RVVRegisterRegAlloc> {
+public:
+  RVVRegisterRegAlloc(const char *N, const char *D, FunctionPassCtor C)
+      : RegisterRegAllocBase(N, D, C) {}
+};
+
+static bool onlyAllocateRVVReg(const TargetRegisterInfo &TRI,
+                               const TargetRegisterClass &RC) {
+  return RISCV::VRRegClass.hasSubClassEq(&RC) ||
+         RISCV::VRM2RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRM4RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRM8RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN2M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN2M2RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN2M4RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN3M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN3M2RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN4M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN4M2RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN5M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN6M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN7M1RegClass.hasSubClassEq(&RC) ||
+         RISCV::VRN8M1RegClass.hasSubClassEq(&RC);
+}
+
+static FunctionPass *useDefaultRegisterAllocator() { return nullptr; }
+
+static llvm::once_flag InitializeDefaultRVVRegisterAllocatorFlag;
+
+/// -riscv-splitRA-rvv-regalloc=... command line option.
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michaelmaitland wrote:

Is `riscv-splitRA-rvv-regalloc` redundant? Why not `riscv-rvv-regalloc`? It looks like that is what AMDGPU does with `sgpr-regalloc` and `vgpr-regalloc`.

https://github.com/llvm/llvm-project/pull/70549