[llvm] [AMDGPU] add missing checks in processBaseWithConstOffset (PR #102310)

[Tim Gymnich via llvm-commits]

================
@@ -2562,4 +2562,99 @@ entry:
   ret void
 }
 
+define amdgpu_kernel void @negativeoffsetnullptr(ptr %buffer) {
+; GFX8-LABEL: negativeoffsetnullptr:
+; GFX8:       ; %bb.0: ; %entry
+; GFX8-NEXT:    s_load_dword s1, s[2:3], 0xec
+; GFX8-NEXT:    s_add_u32 s0, 0, -1
+; GFX8-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX8-NEXT:    s_addc_u32 s1, s1, -1
+; GFX8-NEXT:    v_mov_b32_e32 v0, s0
+; GFX8-NEXT:    v_mov_b32_e32 v1, s1
+; GFX8-NEXT:    flat_load_ubyte v0, v[0:1]
+; GFX8-NEXT:    s_mov_b64 s[0:1], 0
+; GFX8-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
+; GFX8-NEXT:    v_cmp_eq_u16_e32 vcc, 0, v0
+; GFX8-NEXT:  .LBB8_1: ; %branch
+; GFX8-NEXT:    ; =>This Inner Loop Header: Depth=1
+; GFX8-NEXT:    s_and_b64 s[2:3], exec, vcc
+; GFX8-NEXT:    s_or_b64 s[0:1], s[2:3], s[0:1]
+; GFX8-NEXT:    s_andn2_b64 exec, exec, s[0:1]
+; GFX8-NEXT:    s_cbranch_execnz .LBB8_1
+; GFX8-NEXT:  ; %bb.2: ; %end
+; GFX8-NEXT:    s_endpgm
+;
+; GFX9-LABEL: negativeoffsetnullptr:
+; GFX9:       ; %bb.0: ; %entry
+; GFX9-NEXT:    s_mov_b64 s[0:1], src_private_base
+; GFX9-NEXT:    v_mov_b32_e32 v1, s1
+; GFX9-NEXT:    v_add_co_u32_e64 v0, vcc, -1, 0
+; GFX9-NEXT:    v_addc_co_u32_e32 v1, vcc, -1, v1, vcc
+; GFX9-NEXT:    flat_load_ubyte v0, v[0:1]
+; GFX9-NEXT:    s_mov_b64 s[0:1], 0
+; GFX9-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
+; GFX9-NEXT:    v_cmp_eq_u16_e32 vcc, 0, v0
+; GFX9-NEXT:  .LBB8_1: ; %branch
+; GFX9-NEXT:    ; =>This Inner Loop Header: Depth=1
+; GFX9-NEXT:    s_and_b64 s[2:3], exec, vcc
+; GFX9-NEXT:    s_or_b64 s[0:1], s[2:3], s[0:1]
+; GFX9-NEXT:    s_andn2_b64 exec, exec, s[0:1]
+; GFX9-NEXT:    s_cbranch_execnz .LBB8_1
+; GFX9-NEXT:  ; %bb.2: ; %end
+; GFX9-NEXT:    s_endpgm
+;
+; GFX10-LABEL: negativeoffsetnullptr:
+; GFX10:       ; %bb.0: ; %entry
+; GFX10-NEXT:    s_mov_b64 s[0:1], src_private_base
+; GFX10-NEXT:    s_add_u32 s0, 0, -1
+; GFX10-NEXT:    s_addc_u32 s1, s1, -1
+; GFX10-NEXT:    v_mov_b32_e32 v0, s0
+; GFX10-NEXT:    v_mov_b32_e32 v1, s1
+; GFX10-NEXT:    s_mov_b32 s0, 0
+; GFX10-NEXT:    flat_load_ubyte v0, v[0:1]
+; GFX10-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
+; GFX10-NEXT:    v_cmp_eq_u16_e32 vcc_lo, 0, v0
+; GFX10-NEXT:  .LBB8_1: ; %branch
+; GFX10-NEXT:    ; =>This Inner Loop Header: Depth=1
+; GFX10-NEXT:    s_and_b32 s1, exec_lo, vcc_lo
+; GFX10-NEXT:    s_or_b32 s0, s1, s0
+; GFX10-NEXT:    s_andn2_b32 exec_lo, exec_lo, s0
+; GFX10-NEXT:    s_cbranch_execnz .LBB8_1
+; GFX10-NEXT:  ; %bb.2: ; %end
+; GFX10-NEXT:    s_endpgm
+;
+; GFX11-LABEL: negativeoffsetnullptr:
+; GFX11:       ; %bb.0: ; %entry
+; GFX11-NEXT:    s_mov_b64 s[0:1], src_private_base
+; GFX11-NEXT:    v_add_co_u32 v0, s0, -1, 0
+; GFX11-NEXT:    s_delay_alu instid0(VALU_DEP_1)
+; GFX11-NEXT:    v_add_co_ci_u32_e64 v1, null, -1, s1, s0
+; GFX11-NEXT:    s_mov_b32 s0, 0
+; GFX11-NEXT:    flat_load_u8 v0, v[0:1]
+; GFX11-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
+; GFX11-NEXT:    v_cmp_eq_u16_e32 vcc_lo, 0, v0
+; GFX11-NEXT:  .LBB8_1: ; %branch
+; GFX11-NEXT:    ; =>This Inner Loop Header: Depth=1
+; GFX11-NEXT:    s_and_b32 s1, exec_lo, vcc_lo
+; GFX11-NEXT:    s_delay_alu instid0(SALU_CYCLE_1) | instskip(NEXT) | instid1(SALU_CYCLE_1)
+; GFX11-NEXT:    s_or_b32 s0, s1, s0
+; GFX11-NEXT:    s_and_not1_b32 exec_lo, exec_lo, s0
+; GFX11-NEXT:    s_cbranch_execnz .LBB8_1
+; GFX11-NEXT:  ; %bb.2: ; %end
+; GFX11-NEXT:    s_endpgm
+entry:
+  %null = select i1 false, ptr %buffer, ptr addrspacecast (ptr addrspace(5) null to ptr)
----------------
tgymnich wrote:

Good point. That does definitely happen. I'll add a MIR test.

https://github.com/llvm/llvm-project/pull/102310