[AMDGPU] Don't flush vmcnt for loops with use/def pairs
Conditions for hoisting vmcnt with flat instructions should be similar to VMEM.
If there are use/def pairs in a loop body we cannot guarantee that hosting the
waitcnt will be profitable. Better heuristics are needed to analyse whether
gains from avoiding waitcnt in loop bodys outweighs waiting for loads in the
preheader.
Reviewed By: foad
Differential Revision: https://reviews.llvm.org/D151126
diff --git a/llvm/test/CodeGen/AMDGPU/atomicrmw-nand.ll b/llvm/test/CodeGen/AMDGPU/atomicrmw-nand.ll
index fe0543a..5e1f9b0 100644
--- a/llvm/test/CodeGen/AMDGPU/atomicrmw-nand.ll
+++ b/llvm/test/CodeGen/AMDGPU/atomicrmw-nand.ll
@@ -34,9 +34,9 @@
; GCN-NEXT: s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
; GCN-NEXT: global_load_dword v2, v[0:1], off
; GCN-NEXT: s_mov_b64 s[4:5], 0
-; GCN-NEXT: s_waitcnt vmcnt(0)
; GCN-NEXT: .LBB1_1: ; %atomicrmw.start
; GCN-NEXT: ; =>This Inner Loop Header: Depth=1
+; GCN-NEXT: s_waitcnt vmcnt(0)
; GCN-NEXT: v_mov_b32_e32 v3, v2
; GCN-NEXT: v_not_b32_e32 v2, v3
; GCN-NEXT: v_or_b32_e32 v2, -5, v2
@@ -62,10 +62,9 @@
; GCN-NEXT: s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
; GCN-NEXT: flat_load_dword v2, v[0:1]
; GCN-NEXT: s_mov_b64 s[4:5], 0
-; GCN-NEXT: s_waitcnt vmcnt(0)
; GCN-NEXT: .LBB2_1: ; %atomicrmw.start
; GCN-NEXT: ; =>This Inner Loop Header: Depth=1
-; GCN-NEXT: s_waitcnt lgkmcnt(0)
+; GCN-NEXT: s_waitcnt vmcnt(0) lgkmcnt(0)
; GCN-NEXT: v_mov_b32_e32 v3, v2
; GCN-NEXT: v_not_b32_e32 v2, v3
; GCN-NEXT: v_or_b32_e32 v2, -5, v2
