[AMDGPU][Uniformity] V_MBCNT* is never uniform

Mark V_MBCNT instructions add thread/lane position so will never
be uniform.

Reviewed By: foad

Differential Revision: https://reviews.llvm.org/D150759

diff --git a/llvm/lib/Target/AMDGPU/VOP2Instructions.td b/llvm/lib/Target/AMDGPU/VOP2Instructions.td
index 446e7d0..9442b1f 100644 (file)
--- a/llvm/lib/Target/AMDGPU/VOP2Instructions.td
+++ b/llvm/lib/Target/AMDGPU/VOP2Instructions.td
@@ -773,8 +773,10 @@ def V_WRITELANE_B32 : VOP2_Pseudo<"v_writelane_b32", VOP_WRITELANE,
 let isReMaterializable = 1 in {
 defm V_BFM_B32 : VOP2Inst <"v_bfm_b32", VOP_I32_I32_I32>;
 defm V_BCNT_U32_B32 : VOP2Inst <"v_bcnt_u32_b32", VOP_I32_I32_I32, add_ctpop>;
+let IsNeverUniform = 1 in {
 defm V_MBCNT_LO_U32_B32 : VOP2Inst <"v_mbcnt_lo_u32_b32", VOP_I32_I32_I32, int_amdgcn_mbcnt_lo>;
 defm V_MBCNT_HI_U32_B32 : VOP2Inst <"v_mbcnt_hi_u32_b32", VOP_I32_I32_I32, int_amdgcn_mbcnt_hi>;
+} // End IsNeverUniform = 1
 defm V_LDEXP_F32 : VOP2Inst <"v_ldexp_f32", VOP_F32_F32_I32, AMDGPUldexp>;
 
 let ReadsModeReg = 0, mayRaiseFPException = 0 in {

diff --git a/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform.mir b/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform.mir
index fa22890..9a7e755 100644 (file)
--- a/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform.mir
+++ b/llvm/test/Analysis/UniformityAnalysis/AMDGPU/MIR/never-uniform.mir
@@ -140,3 +140,26 @@ body:             |
     %5:vgpr_32 = V_AND_B32_e32 $vgpr4, $vgpr5, implicit $exec
     S_ENDPGM 0
 ...
+# mbcnt instructions are not uniform
+---
+name:            mbcnt_lo
+machineFunctionInfo:
+  isEntryFunction: true
+body:             |
+  bb.0:
+    ; CHECK-LABEL: MachineUniformityInfo for function: mbcnt_lo
+    ; CHECK: DIVERGENT: %0
+    %0:vgpr_32 = V_MBCNT_LO_U32_B32_e64 -1, 0, implicit $exec
+    S_ENDPGM 0
+...
+---
+name:            mbcnt_hi
+machineFunctionInfo:
+  isEntryFunction: true
+body:             |
+  bb.0:
+    ; CHECK-LABEL: MachineUniformityInfo for function: mbcnt_hi
+    ; CHECK: DIVERGENT: %0
+    %0:vgpr_32 = V_MBCNT_HI_U32_B32_e64 -1, 0, implicit $exec
+    S_ENDPGM 0
+...