[AMDGPU] Emit S_CBRANCH_SCC for floating-point conditions.

Author: Konstantina Mitropoulou

llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp

@@ -2390,12 +2390,14 @@ bool AMDGPUDAGToDAGISel::isCBranchSCC(const SDNode *N) const {
     return true;
 
   if (VT == MVT::i64) {
-    const auto *ST = static_cast<const GCNSubtarget *>(Subtarget);
-
     ISD::CondCode CC = cast<CondCodeSDNode>(Cond.getOperand(2))->get();
-    return (CC == ISD::SETEQ || CC == ISD::SETNE) && ST->hasScalarCompareEq64();
+    return (CC == ISD::SETEQ || CC == ISD::SETNE) &&
+           Subtarget->hasScalarCompareEq64();
   }
 
+  if ((VT == MVT::f16 || VT == MVT::f32) && ST->hasSALUFloatInsts())
+    return true;
+
   return false;
 }
 

llvm/test/CodeGen/AMDGPU/branch-relaxation.ll

@@ -297,10 +297,7 @@ define amdgpu_kernel void @uniform_conditional_min_long_forward_vcnd_branch(ptr
 ; GFX12-NEXT:    s_load_b32 s0, s[4:5], 0x2c
 ; GFX12-NEXT:    s_wait_kmcnt 0x0
 ; GFX12-NEXT:    s_cmp_eq_f32 s0, 0
-; GFX12-NEXT:    s_cselect_b32 s1, -1, 0
-; GFX12-NEXT:    s_delay_alu instid0(SALU_CYCLE_1)
-; GFX12-NEXT:    s_and_b32 vcc_lo, exec_lo, s1
-; GFX12-NEXT:    s_cbranch_vccz .LBB2_1
+; GFX12-NEXT:    s_cbranch_scc0 .LBB2_1
 ; GFX12-NEXT:  ; %bb.3: ; %bb0
 ; GFX12-NEXT:    s_getpc_b64 s[2:3]
 ; GFX12-NEXT:  .Lpost_getpc2:

llvm/test/CodeGen/AMDGPU/uniform_branch_with_floating_point_cond.ll

@@ -15,10 +15,7 @@ define void @test() {
   ; CHECK-NEXT:   [[S_LOAD_DWORD_IMM:%[0-9]+]]:sreg_32_xm0_xexec = S_LOAD_DWORD_IMM killed [[S_LOAD_DWORDX2_IMM]], 0, 0 :: (dereferenceable invariant load (s32) from @external_constant1, addrspace 4)
   ; CHECK-NEXT:   [[S_MOV_B32_:%[0-9]+]]:sgpr_32 = S_MOV_B32 0
   ; CHECK-NEXT:   nofpexcept S_CMP_LG_F32 killed [[S_LOAD_DWORD_IMM]], killed [[S_MOV_B32_]], implicit-def $scc, implicit $mode
-  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:sreg_32 = COPY $scc
-  ; CHECK-NEXT:   [[S_AND_B32_:%[0-9]+]]:sreg_32 = S_AND_B32 $exec_lo, killed [[COPY]], implicit-def dead $scc
-  ; CHECK-NEXT:   $vcc_lo = COPY [[S_AND_B32_]]
-  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.3, implicit $vcc
+  ; CHECK-NEXT:   S_CBRANCH_SCC1 %bb.3, implicit $scc
   ; CHECK-NEXT:   S_BRANCH %bb.1
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.1.bb1:
@@ -31,12 +28,9 @@ define void @test() {
   ; CHECK-NEXT:   [[GLOBAL_LOAD_DWORD_SADDR:%[0-9]+]]:vgpr_32 = GLOBAL_LOAD_DWORD_SADDR killed [[S_LOAD_DWORDX2_IMM2]], killed [[V_MOV_B32_e32_]], 0, 0, implicit $exec :: (load (s32) from %ir.0, addrspace 1)
   ; CHECK-NEXT:   [[S_MOV_B32_1:%[0-9]+]]:sgpr_32 = S_MOV_B32 1092616192
   ; CHECK-NEXT:   [[S_MOV_B32_2:%[0-9]+]]:sgpr_32 = S_MOV_B32 1065353216
-  ; CHECK-NEXT:   [[COPY1:%[0-9]+]]:sreg_32 = COPY [[GLOBAL_LOAD_DWORD_SADDR]]
-  ; CHECK-NEXT:   nofpexcept S_CMP_LT_F32 killed [[COPY1]], killed [[S_MOV_B32_2]], implicit-def $scc, implicit $mode
-  ; CHECK-NEXT:   [[COPY2:%[0-9]+]]:sreg_32 = COPY $scc
-  ; CHECK-NEXT:   [[S_AND_B32_1:%[0-9]+]]:sreg_32 = S_AND_B32 $exec_lo, killed [[COPY2]], implicit-def dead $scc
-  ; CHECK-NEXT:   $vcc_lo = COPY [[S_AND_B32_1]]
-  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.4, implicit $vcc
+  ; CHECK-NEXT:   [[COPY:%[0-9]+]]:sreg_32 = COPY [[GLOBAL_LOAD_DWORD_SADDR]]
+  ; CHECK-NEXT:   nofpexcept S_CMP_LT_F32 killed [[COPY]], killed [[S_MOV_B32_2]], implicit-def $scc, implicit $mode
+  ; CHECK-NEXT:   S_CBRANCH_SCC1 %bb.4, implicit $scc
   ; CHECK-NEXT:   S_BRANCH %bb.2
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.2.bb2:
@@ -56,10 +50,7 @@ define void @test() {
   ; CHECK-NEXT:   [[PHI:%[0-9]+]]:sgpr_32 = PHI [[S_MOV_B32_1]], %bb.1, [[S_MOV_B32_3]], %bb.2
   ; CHECK-NEXT:   [[S_MOV_B32_4:%[0-9]+]]:sgpr_32 = S_MOV_B32 0
   ; CHECK-NEXT:   nofpexcept S_CMP_NEQ_F32 [[PHI]], killed [[S_MOV_B32_4]], implicit-def $scc, implicit $mode
-  ; CHECK-NEXT:   [[COPY3:%[0-9]+]]:sreg_32 = COPY $scc
-  ; CHECK-NEXT:   [[S_AND_B32_2:%[0-9]+]]:sreg_32 = S_AND_B32 $exec_lo, killed [[COPY3]], implicit-def dead $scc
-  ; CHECK-NEXT:   $vcc_lo = COPY [[S_AND_B32_2]]
-  ; CHECK-NEXT:   S_CBRANCH_VCCNZ %bb.6, implicit $vcc
+  ; CHECK-NEXT:   S_CBRANCH_SCC1 %bb.6, implicit $scc
   ; CHECK-NEXT:   S_BRANCH %bb.5
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.5.bb4: