[llvm] Mark permlane instructions as convergent (PR #142962)

[Paul Trojahn via llvm-commits]

https://github.com/ptrojahn created https://github.com/llvm/llvm-project/pull/142962

Not sure if this is the right place to add this, but without explicitly setting it as convergent, the permlanex16 instruction in the test sinks into the second block.

>From c1b2b5202a7469c0048879d1e14ebba1fe4f7b27 Mon Sep 17 00:00:00 2001
From: Paul Trojahn <paul.trojahn at amd.com>
Date: Wed, 4 Jun 2025 14:51:46 +0200
Subject: [PATCH] Mark permlane instructions as convergent

Not sure if this is the right place to add this, but without
explicitly setting it as convergent, the permlanex16 instruction
in the test sinks into the second block.
---
 llvm/lib/Target/AMDGPU/VOP3Instructions.td    |  4 +-
 .../CodeGen/AMDGPU/llvm.amdgcn.permlane.ll    | 68 +++++++++++++++++++
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/VOP3Instructions.td b/llvm/lib/Target/AMDGPU/VOP3Instructions.td
index a2672d71cb43c..d63a0c102152a 100644
--- a/llvm/lib/Target/AMDGPU/VOP3Instructions.td
+++ b/llvm/lib/Target/AMDGPU/VOP3Instructions.td
@@ -1333,10 +1333,10 @@ let SubtargetPredicate = isGFX10Plus in {
   } // End isCommutable = 1, isReMaterializable = 1
   def : ThreeOp_i32_Pats<xor, xor, V_XOR3_B32_e64>;
 
-  let Constraints = "$vdst = $vdst_in", DisableEncoding="$vdst_in" in {
+  let Constraints = "$vdst = $vdst_in", DisableEncoding="$vdst_in", isConvergent = 1 in {
     defm V_PERMLANE16_B32 : VOP3Inst<"v_permlane16_b32", VOP3_PERMLANE_Profile>;
     defm V_PERMLANEX16_B32 : VOP3Inst<"v_permlanex16_b32", VOP3_PERMLANE_Profile>;
-  } // End $vdst = $vdst_in, DisableEncoding $vdst_in
+  } // End $vdst = $vdst_in, DisableEncoding $vdst_in, isConvergent = 1
 
   foreach vt = Reg32Types.types in {
     def : PermlanePat<int_amdgcn_permlane16, V_PERMLANE16_B32_e64, vt>;
diff --git a/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.permlane.ll b/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.permlane.ll
index 693e0ebd0280c..d05501fb0c8b7 100644
--- a/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.permlane.ll
+++ b/llvm/test/CodeGen/AMDGPU/llvm.amdgcn.permlane.ll
@@ -10410,3 +10410,71 @@ define void @v_permlanex16_v8f64(ptr addrspace(1) %out, <8 x double> %src0, i32
   store <8 x double> %v, ptr addrspace(1) %out
   ret void
 }
+
+define amdgpu_kernel void @v_permlanex16_convergent(ptr addrspace(1) %out, i32 %src0, i32 %pattern_lo, i32 %pattern_hi) {
+; GFX10-LABEL: v_permlanex16_convergent:
+; GFX10:       ; %bb.0:
+; GFX10-NEXT:    s_clause 0x1
+; GFX10-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x2c
+; GFX10-NEXT:    s_load_dword s2, s[4:5], 0x34
+; GFX10-NEXT:    v_cmp_eq_u32_e32 vcc_lo, 0, v0
+; GFX10-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX10-NEXT:    v_mov_b32_e32 v1, s0
+; GFX10-NEXT:    v_permlanex16_b32 v1, v1, s1, s2
+; GFX10-NEXT:    s_and_saveexec_b32 s0, vcc_lo
+; GFX10-NEXT:    s_cbranch_execz .LBB142_2
+; GFX10-NEXT:  ; %bb.1: ; %t
+; GFX10-NEXT:    s_load_dwordx2 s[0:1], s[4:5], 0x24
+; GFX10-NEXT:    v_mov_b32_e32 v0, 0
+; GFX10-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX10-NEXT:    global_store_dword v0, v1, s[0:1]
+; GFX10-NEXT:  .LBB142_2: ; %f
+; GFX10-NEXT:    s_endpgm
+;
+; GFX11-LABEL: v_permlanex16_convergent:
+; GFX11:       ; %bb.0:
+; GFX11-NEXT:    s_clause 0x1
+; GFX11-NEXT:    s_load_b64 s[0:1], s[4:5], 0x2c
+; GFX11-NEXT:    s_load_b32 s2, s[4:5], 0x34
+; GFX11-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX11-NEXT:    v_dual_mov_b32 v1, s0 :: v_dual_and_b32 v0, 0x3ff, v0
+; GFX11-NEXT:    s_mov_b32 s0, exec_lo
+; GFX11-NEXT:    s_delay_alu instid0(VALU_DEP_1) | instskip(NEXT) | instid1(VALU_DEP_2)
+; GFX11-NEXT:    v_permlanex16_b32 v1, v1, s1, s2
+; GFX11-NEXT:    v_cmpx_eq_u32_e32 0, v0
+; GFX11-NEXT:    s_cbranch_execz .LBB142_2
+; GFX11-NEXT:  ; %bb.1: ; %t
+; GFX11-NEXT:    s_load_b64 s[0:1], s[4:5], 0x24
+; GFX11-NEXT:    v_mov_b32_e32 v0, 0
+; GFX11-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX11-NEXT:    global_store_b32 v0, v1, s[0:1]
+; GFX11-NEXT:  .LBB142_2: ; %f
+; GFX11-NEXT:    s_endpgm
+;
+; GFX12-LABEL: v_permlanex16_convergent:
+; GFX12:       ; %bb.0:
+; GFX12-NEXT:    s_load_b96 s[0:2], s[4:5], 0x2c
+; GFX12-NEXT:    s_wait_kmcnt 0x0
+; GFX12-NEXT:    v_dual_mov_b32 v1, s0 :: v_dual_and_b32 v0, 0x3ff, v0
+; GFX12-NEXT:    s_mov_b32 s0, exec_lo
+; GFX12-NEXT:    s_delay_alu instid0(VALU_DEP_1) | instskip(NEXT) | instid1(VALU_DEP_2)
+; GFX12-NEXT:    v_permlanex16_b32 v1, v1, s1, s2
+; GFX12-NEXT:    v_cmpx_eq_u32_e32 0, v0
+; GFX12-NEXT:    s_cbranch_execz .LBB142_2
+; GFX12-NEXT:  ; %bb.1: ; %t
+; GFX12-NEXT:    s_load_b64 s[0:1], s[4:5], 0x24
+; GFX12-NEXT:    v_mov_b32_e32 v0, 0
+; GFX12-NEXT:    s_wait_kmcnt 0x0
+; GFX12-NEXT:    global_store_b32 v0, v1, s[0:1]
+; GFX12-NEXT:  .LBB142_2: ; %f
+; GFX12-NEXT:    s_endpgm
+  %tidx = call i32 @llvm.amdgcn.workitem.id.x()
+  %v = call i32 @llvm.amdgcn.permlanex16.i32(i32 %src0, i32 %src0, i32 %pattern_lo, i32 %pattern_hi, i1 false, i1 false)
+  %select = icmp eq i32 %tidx, 0
+  br i1 %select, label %t, label %f
+t:
+  store i32 %v, ptr addrspace(1) %out
+  br label %f
+f:
+  ret void
+}