[PATCH] D125971: [RISCV] Ensure the forwarded AVL register is alive

[Lorenzo Albano via Phabricator via llvm-commits]

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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125971

Files:
  llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
  llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll


Index: llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
+++ llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.ll
@@ -493,6 +493,20 @@
   ret i64 %vl
 }
 
+; 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>,
Index: llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -1234,8 +1234,10 @@
                 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;
               }


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