[AMDGPU] Do not check denorm for LDS FP atomic with unsafe flag

[rampitec]

Summary

This is already how it is handled for global and flat atomics.

[rampitec]

Rebased.

[t-tye]

LGTM

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

if ((AS == AMDGPUAS::GLOBAL_ADDRESS || AS == AMDGPUAS::FLAT_ADDRESS) &&
       return RMW->use_empty() ? AtomicExpansionKind::None :
                                 AtomicExpansionKind::CmpXChg;
     }
 
     // DS FP atomics do repect the denormal mode, but the rounding mode is fixed
     // to round-to-nearest-even.
     // The only exception is DS_ADD_F64 which never flushes regardless of mode.
     if (AS == AMDGPUAS::LOCAL_ADDRESS && Subtarget->hasLDSFPAtomics()) {
-      return (Ty->isDoubleTy() && !fpModeMatchesGlobalFPAtomicMode(RMW)) ?
-        AtomicExpansionKind::CmpXChg : AtomicExpansionKind::None;
+      if (!Ty->isDoubleTy())
+        return AtomicExpansionKind::None;
+
+      return (fpModeMatchesGlobalFPAtomicMode(RMW) ||
+              RMW->getFunction()
+                      ->getFnAttribute("amdgpu-unsafe-fp-atomics")
+                      .getValueAsString() == "true")
+                 ? AtomicExpansionKind::None
+                 : AtomicExpansionKind::CmpXChg;
     }
 
     return AtomicExpansionKind::CmpXChg;
   }
   default:
     break;
   }
 

llvm/test/CodeGen/AMDGPU/fp64-atomics-gfx90a.ll

main_body:
   %ret = atomicrmw fadd double addrspace(3)* %ptr, double 4.0 seq_cst
   ret void
 }
 
 define amdgpu_kernel void @local_atomic_fadd_f64_noret_pat_flush(double addrspace(3)* %ptr) #0 {
 ; GFX90A-LABEL: local_atomic_fadd_f64_noret_pat_flush:
 ; GFX90A:       ; %bb.0: ; %main_body
 ; GFX90A-NEXT:    s_load_dword s0, s[0:1], 0x24
+; GFX90A-NEXT:    v_mov_b32_e32 v0, 0
+; GFX90A-NEXT:    v_mov_b32_e32 v1, 0x40100000
+; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX90A-NEXT:    v_mov_b32_e32 v2, s0
+; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX90A-NEXT:    ds_add_f64 v2, v[0:1]
+; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX90A-NEXT:    s_endpgm
+main_body:
+  %ret = atomicrmw fadd double addrspace(3)* %ptr, double 4.0 seq_cst
+  ret void
+}
+
+define amdgpu_kernel void @local_atomic_fadd_f64_noret_pat_flush_safe(double addrspace(3)* %ptr) #4 {
+; GFX90A-LABEL: local_atomic_fadd_f64_noret_pat_flush_safe:
+; GFX90A:       ; %bb.0: ; %main_body
+; GFX90A-NEXT:    s_load_dword s0, s[0:1], 0x24
 ; GFX90A-NEXT:    s_mov_b64 s[2:3], 0
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    v_mov_b32_e32 v0, s0
 ; GFX90A-NEXT:    ds_read_b64 v[0:1], v0
-; GFX90A-NEXT:  BB49_1: ; %atomicrmw.start
+; GFX90A-NEXT:  BB50_1: ; %atomicrmw.start
 ; GFX90A-NEXT:    ; =>This Inner Loop Header: Depth=1
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    v_add_f64 v[2:3], v[0:1], 4.0
 ; GFX90A-NEXT:    v_mov_b32_e32 v4, s0
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    ds_cmpst_rtn_b64 v[2:3], v4, v[0:1], v[2:3]
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    v_cmp_eq_u64_e32 vcc, v[2:3], v[0:1]
 ; GFX90A-NEXT:    s_or_b64 s[2:3], vcc, s[2:3]
 ; GFX90A-NEXT:    v_pk_mov_b32 v[0:1], v[2:3], v[2:3] op_sel:[0,1]
 ; GFX90A-NEXT:    s_andn2_b64 exec, exec, s[2:3]
-; GFX90A-NEXT:    s_cbranch_execnz BB49_1
+; GFX90A-NEXT:    s_cbranch_execnz BB50_1
 ; GFX90A-NEXT:  ; %bb.2: ; %atomicrmw.end
 ; GFX90A-NEXT:    s_endpgm
 main_body:
   %ret = atomicrmw fadd double addrspace(3)* %ptr, double 4.0 seq_cst
   ret void
 }
 
 define double @local_atomic_fadd_f64_rtn_pat(double addrspace(3)* %ptr, double %data) #1 {
 ; GFX90A-LABEL: local_atomic_fadd_f64_rtn_pat:
 ; GFX90A:       ; %bb.0: ; %main_body
 ; GFX90A-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GFX90A-NEXT:    v_mov_b32_e32 v2, 0
 ; GFX90A-NEXT:    v_mov_b32_e32 v3, 0x40100000
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    ds_add_rtn_f64 v[0:1], v0, v[2:3]
 ; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX90A-NEXT:    s_setpc_b64 s[30:31]
 main_body:
   %ret = atomicrmw fadd double addrspace(3)* %ptr, double 4.0 seq_cst
   ret double %ret
 }
 
+define double @local_atomic_fadd_f64_rtn_ieee_unsafe(double addrspace(3)* %ptr, double %data) #2 {
+; GFX90A-LABEL: local_atomic_fadd_f64_rtn_ieee_unsafe:
+; GFX90A:       ; %bb.0: ; %main_body
+; GFX90A-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX90A-NEXT:    v_mov_b32_e32 v3, v2
+; GFX90A-NEXT:    v_mov_b32_e32 v2, v1
+; GFX90A-NEXT:    ds_add_rtn_f64 v[0:1], v0, v[2:3]
+; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX90A-NEXT:    s_setpc_b64 s[30:31]
+main_body:
+  %ret = call double @llvm.amdgcn.ds.fadd.f64(double addrspace(3)* %ptr, double %data, i32 0, i32 0, i1 0)
+  ret double %ret
+}
+
+define double @local_atomic_fadd_f64_rtn_ieee_safe(double addrspace(3)* %ptr, double %data) #3 {
+; GFX90A-LABEL: local_atomic_fadd_f64_rtn_ieee_safe:
+; GFX90A:       ; %bb.0: ; %main_body
+; GFX90A-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX90A-NEXT:    v_mov_b32_e32 v3, v2
+; GFX90A-NEXT:    v_mov_b32_e32 v2, v1
+; GFX90A-NEXT:    ds_add_rtn_f64 v[0:1], v0, v[2:3]
+; GFX90A-NEXT:    s_waitcnt lgkmcnt(0)
+; GFX90A-NEXT:    s_setpc_b64 s[30:31]
+main_body:
+  %ret = call double @llvm.amdgcn.ds.fadd.f64(double addrspace(3)* %ptr, double %data, i32 0, i32 0, i1 0)
+  ret double %ret
+}
+
 attributes #0 = { "denormal-fp-math"="preserve-sign,preserve-sign" "amdgpu-unsafe-fp-atomics"="true" }
 attributes #1 = { "amdgpu-unsafe-fp-atomics"="true" }
+attributes #2 = { "denormal-fp-math"="ieee,ieee" "amdgpu-unsafe-fp-atomics"="true" }
+attributes #3 = { "denormal-fp-math"="ieee,ieee" }
+attributes #4 = { "denormal-fp-math"="preserve-sign,preserve-sign" }