From 948d931323a13dfc68430814a44b9075a59e2310 Mon Sep 17 00:00:00 2001
From: Philip Reames <preames@rivosinc.com>
Date: Tue, 24 May 2022 14:58:09 -0700
Subject: [PATCH] [RISCV] Ensure the forwarded AVL register is alive

When the AVL value does not fit in 5 bits, the register in which this value is stored may be dead when we want to forward it. This patch ensure the kill flags on the register are cleared before forwarding.

Patch by: loralb
Differential Revision: https://reviews.llvm.org/D125971
---
 llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp  |  4 +++-
 llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index 330fc8e..2a1cdec 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -1239,8 +1239,10 @@ void RISCVInsertVSETVLI::doLocalPrepass(MachineBasicBlock &MBB) {
                 MachineOperand &VLOp = MI.getOperand(getVLOpNum(MI));
                 if (CurInfo.hasAVLImm())
                   VLOp.ChangeToImmediate(CurInfo.getAVLImm());
-                else
+                else {
+                  MRI->clearKillFlags(CurInfo.getAVLReg());
                   VLOp.ChangeToRegister(CurInfo.getAVLReg(), /*IsDef*/ false);
+                }
                 CurInfo = computeInfoForInstr(MI, TSFlags, MRI);
                 continue;
               }
diff --git a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
index 4e0364e..e625e44 100644
--- a/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
@@ -521,6 +521,20 @@ declare { <vscale x 1 x i64>, i64 } @llvm.riscv.vleff.nxv1i64.i64(
 declare <vscale x 1 x i1> @llvm.riscv.vmseq.nxv1i64.i64.i64(
   <vscale x 1 x i64>, i64, i64)
 
+; Ensure AVL register is alive when forwarding an AVL immediate that does not fit in 5 bits
+define <vscale x 2 x i32> @avl_forward5(<vscale x 2 x i32>* %addr) {
+; CHECK-LABEL: avl_forward5:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a1, 32
+; CHECK-NEXT:    vsetvli zero, a1, e8, m4, ta, mu
+; CHECK-NEXT:    vsetvli zero, a1, e32, m1, ta, mu
+; CHECK-NEXT:    vle32.v v8, (a0)
+; CHECK-NEXT:    ret
+  %gvl = tail call i64 @llvm.riscv.vsetvli.i64(i64 32, i64 0, i64 2)
+  %ret = tail call <vscale x 2 x i32> @llvm.riscv.vle.nxv2i32.i64(<vscale x 2 x i32> undef, <vscale x 2 x i32>* %addr, i64 %gvl)
+  ret <vscale x 2 x i32> %ret
+}
+
 declare <vscale x 1 x i64> @llvm.riscv.vadd.mask.nxv1i64.nxv1i64(
   <vscale x 1 x i64>,
   <vscale x 1 x i64>,
-- 
2.7.4