[NVPTX] Support fence instruction (#99649)

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Differential Revision: https://phabricator.intern.facebook.com/D60250530

Author: gonzalobg

llvm/lib/Target/NVPTX/NVPTXInstrInfo.td

@@ -3908,3 +3908,31 @@ def : Pat <
   (V2I32toI64
     (INT_NVVM_PRMT (I64toI32H Int64Regs:$a), (i32 0), (i32 0x0123)),
     (INT_NVVM_PRMT (I64toI32L Int64Regs:$a), (i32 0), (i32 0x0123)))>;
+
+
+////////////////////////////////////////////////////////////////////////////////
+// PTX Fence instructions
+////////////////////////////////////////////////////////////////////////////////
+
+def atomic_thread_fence_seq_cst_sys :
+  NVPTXInst<(outs), (ins), "fence.sc.sys;", []>,
+  Requires<[hasPTX<60>, hasSM<70>]>;
+def atomic_thread_fence_acq_rel_sys :
+  NVPTXInst<(outs), (ins), "fence.acq_rel.sys;", []>,
+  Requires<[hasPTX<60>, hasSM<70>]>;
+
+def : Pat<(atomic_fence (i64 4), (i64 1)), (atomic_thread_fence_acq_rel_sys)>, // acquire(4) sys(1)
+      Requires<[hasPTX<60>, hasSM<70>]>;
+def : Pat<(atomic_fence (i64 5), (i64 1)), (atomic_thread_fence_acq_rel_sys)>, // release(5) sys(1)
+      Requires<[hasPTX<60>, hasSM<70>]>;
+def : Pat<(atomic_fence (i64 6), (i64 1)), (atomic_thread_fence_acq_rel_sys)>, // acq_rel(6) sys(1)
+      Requires<[hasPTX<60>, hasSM<70>]>;
+def : Pat<(atomic_fence (i64 7), (i64 1)), (atomic_thread_fence_seq_cst_sys)>, // seq_cst(7) sys(1)
+      Requires<[hasPTX<60>, hasSM<70>]>;
+
+
+// If PTX<60 or SM<70, we fall back to MEMBAR:
+def : Pat<(atomic_fence (i64 4), (i64 1)), (INT_MEMBAR_SYS)>; // acquire(4) sys(1)
+def : Pat<(atomic_fence (i64 5), (i64 1)), (INT_MEMBAR_SYS)>; // release(5) sys(1)
+def : Pat<(atomic_fence (i64 6), (i64 1)), (INT_MEMBAR_SYS)>; // acq_rel(6) sys(1)
+def : Pat<(atomic_fence (i64 7), (i64 1)), (INT_MEMBAR_SYS)>; // seq_cst(7) sys(1)

llvm/test/CodeGen/NVPTX/fence.ll

@@ -0,0 +1,36 @@
+; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 | FileCheck %s --check-prefix=SM60
+; RUN: %if ptxas %{ llc < %s -march=nvptx64 -mcpu=sm_20 | %ptxas-verify %}
+; RUN: llc < %s -march=nvptx64 -mcpu=sm_70 -mattr=+ptx60 | FileCheck %s  --check-prefix=SM70
+; RUN: %if ptxas-12.2 %{ llc < %s -march=nvptx64 -mcpu=sm_70 -mattr=+ptx60 | %ptxas-verify -arch=sm_70 %}
+
+; CHECK-LABEL: fence_sc_sys
+define void @fence_sc_sys() local_unnamed_addr {
+  ; SM60: membar.sys
+  ; SM70: fence.sc.sys
+  fence seq_cst
+  ret void
+}
+
+; CHECK-LABEL: fence_acq_rel_sys
+define void @fence_acq_rel_sys() local_unnamed_addr {
+  ; SM60: membar.sys
+  ; SM70: fence.acq_rel.sys
+  fence acq_rel
+  ret void  
+}
+
+; CHECK-LABEL: fence_release_sys
+define void @fence_release_sys() local_unnamed_addr {
+  ; SM60: membar.sys
+  ; SM70: fence.acq_rel.sys  
+  fence release
+  ret void  
+}
+
+; CHECK-LABEL: fence_acquire_sys
+define void @fence_acquire_sys() local_unnamed_addr {
+  ; SM60: membar.sys
+  ; SM70: fence.acq_rel.sys  
+  fence acquire
+  ret void  
+}