AMDGPU: Handle invariant when lowering global loads

Global with invariant should be treated identically to
constant.

Author: arsenm

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -11944,7 +11944,7 @@ SDValue SITargetLowering::LowerLOAD(SDValue Op, SelectionDAG &DAG) const {
       AS == AMDGPUAS::CONSTANT_ADDRESS_32BIT ||
       (AS == AMDGPUAS::GLOBAL_ADDRESS &&
        Subtarget->getScalarizeGlobalBehavior() && Load->isSimple() &&
-       isMemOpHasNoClobberedMemOperand(Load))) {
+       (Load->isInvariant() || isMemOpHasNoClobberedMemOperand(Load)))) {
     if ((!Op->isDivergent() || AMDGPU::isUniformMMO(MMO)) &&
         Alignment >= Align(4) && NumElements < 32) {
       if (MemVT.isPow2VectorType() ||

llvm/test/CodeGen/AMDGPU/load-global-invariant.ll

@@ -50,15 +50,22 @@ define amdgpu_kernel void @load_global_v3i64(ptr addrspace(1) %dst, ptr addrspac
 define amdgpu_kernel void @load_global_v3i64_invariant(ptr addrspace(1) %dst, ptr addrspace(1) %src) #0 {
 ; CHECK-LABEL: load_global_v3i64_invariant:
 ; CHECK:       ; %bb.0:
-; CHECK-NEXT:    v_mov_b32_e32 v6, 0
-; CHECK-NEXT:    s_load_dwordx2 s[0:1], s[8:9], 0x0
-; CHECK-NEXT:    s_load_dwordx2 s[2:3], s[8:9], 0x8
+; CHECK-NEXT:    v_mov_b32_e32 v4, 0
+; CHECK-NEXT:    s_load_dwordx2 s[4:5], s[8:9], 0x0
+; CHECK-NEXT:    s_load_dwordx2 s[6:7], s[8:9], 0x8
 ; CHECK-NEXT:    s_waitcnt lgkmcnt(0)
-; CHECK-NEXT:    global_load_dwordx4 v[0:3], v6, s[2:3]
-; CHECK-NEXT:    global_load_dwordx2 v[4:5], v6, s[2:3] offset:16
-; CHECK-NEXT:    s_waitcnt vmcnt(0)
-; CHECK-NEXT:    global_store_dwordx2 v6, v[4:5], s[0:1] offset:16
-; CHECK-NEXT:    global_store_dwordx4 v6, v[0:3], s[0:1]
+; CHECK-NEXT:    s_load_dwordx4 s[0:3], s[6:7], 0x0
+; CHECK-NEXT:    s_nop 0
+; CHECK-NEXT:    s_load_dwordx2 s[6:7], s[6:7], 0x10
+; CHECK-NEXT:    s_waitcnt lgkmcnt(0)
+; CHECK-NEXT:    v_mov_b32_e32 v0, s6
+; CHECK-NEXT:    v_mov_b32_e32 v1, s7
+; CHECK-NEXT:    global_store_dwordx2 v4, v[0:1], s[4:5] offset:16
+; CHECK-NEXT:    v_mov_b32_e32 v0, s0
+; CHECK-NEXT:    v_mov_b32_e32 v1, s1
+; CHECK-NEXT:    v_mov_b32_e32 v2, s2
+; CHECK-NEXT:    v_mov_b32_e32 v3, s3
+; CHECK-NEXT:    global_store_dwordx4 v4, v[0:3], s[4:5]
 ; CHECK-NEXT:    s_endpgm
   %ld = load <3 x i64>, ptr addrspace(1) %src, align 32, !invariant.load !0
   store <3 x i64> %ld, ptr addrspace(1) %dst, align 32