[AMDGPU] Ensure return address is save/restored if clobbered or when function has calls

[RamNalamothu]

Summary

This test is to make sure the return address registers, if clobbered in the
function or when the function has calls, are save/restored irrespective of
whether the IPRA is enabled/disabled.

This test is found to be not save/restore the return address registers, when
clobbered in the function, with the corresponding downstream changes of D114652.

The test could not be reduced further as the register allocator needs enough
register pressure so that it allocates the return address registers as well.

[arsenm]

An artificial test with high pressure would be more reliable long term. Branches on constants could be fragile

[RamNalamothu]

In D120922#3363739, @arsenm wrote:

An artificial test with high pressure would be more reliable long term. Branches on constants could be fragile

I will make a note of this in the test so that it can be updated later and will proceed with the test in its current form to unblock my work. Thank you.

llvm/test/CodeGen/AMDGPU/ipra-return-address-save-restore.ll

+; RUN: llc -mtriple=amdgcn-amd-amdhsa -verify-machineinstrs -enable-ipra=1 < %s | FileCheck -check-prefix=GCN %s
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -verify-machineinstrs -enable-ipra=0 < %s | FileCheck -check-prefix=GCN %s
+
+; This test is to make sure the return address registers, if clobbered in the
+; function or the function has calls, are save/restored when IPRA is enabled/disabled.
+
+; TODO: An artificial test with high register pressure would be more reliable in the
+; long run as branches on constants could be fragile.
+
+%struct.ShaderData = type { <3 x float>, <3 x float>, <3 x float>, <3 x float>, i32, i32, i32, i32, i32, float, float, i32, i32, float, float, %struct.differential3, %struct.differential3, %struct.differential, %struct.differential, <3 x float>, <3 x float>, <3 x float>, %struct.differential3, i32, i32, i32, float, <3 x float>, <3 x float>, <3 x float>, [1 x %struct.ShaderClosure] }
+%struct.differential = type { float, float }
+%struct.differential3 = type { <3 x float>, <3 x float> }
+%struct.ShaderClosure = type { <3 x float>, i32, float, <3 x float>, [10 x float], [8 x i8] }
+%struct.MicrofacetExtra = type { <3 x float>, <3 x float>, <3 x float>, float, [12 x i8] }
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare float @llvm.fmuladd.f32(float, float, float) #0
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare <3 x float> @llvm.fmuladd.v3f32(<3 x float>, <3 x float>, <3 x float>) #0
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare <4 x float> @llvm.fmuladd.v4f32(<4 x float>, <4 x float>, <4 x float>) #0
+
+; Function Attrs: argmemonly nofree nosync nounwind willreturn
+declare void @llvm.lifetime.end.p5i8(i64 immarg, i8 addrspace(5)* nocapture) #1
+
+; Function Attrs: norecurse
+define internal fastcc void @svm_node_closure_bsdf(%struct.ShaderData addrspace(1)* %sd, float* %stack, <4 x i32> %node, i32* %offset, i32 %0, i8 %trunc, float %1, float %2, float %mul80, i1 %cmp412.old, <4 x i32> %3, float %4, i32 %5, i1 %cmp440, i1 %cmp442, i1 %or.cond1306, float %.op, %struct.ShaderClosure addrspace(1)* %arrayidx.i.i2202, %struct.ShaderClosure addrspace(1)* %retval.0.i.i22089, %struct.ShaderClosure addrspace(1)* %retval.1.i221310, i1 %cmp575, i32 addrspace(1)* %num_closure_left.i2215, i32 %6, i1 %cmp.i2216, i32 %7, i64 %idx.ext.i2223, i32 %sub5.i2221) #2 {
+; GCN-LABEL: {{^}}svm_node_closure_bsdf:
+; GCN-NOT: s30,
+; GCN-NOT: s31,
+; GCN: s_waitcnt vmcnt(0)
+; GCN: s_setpc_b64 s[30:31]
+; GCN: .size   svm_node_closure_bsdf
+entry:
+  %8 = extractelement <4 x i32> %node, i64 0
+  %cmp.i.not = icmp eq i32 undef, 0
+  br i1 undef, label %common.ret.critedge, label %cond.true
+
+cond.true:                                        ; preds = %entry
+  %9 = load float, float* null, align 4
+  %phi.cmp = fcmp oeq float %9, 0.000000e+00
+  br i1 %phi.cmp, label %common.ret, label %cond.true20
+
+cond.true20:                                      ; preds = %cond.true
+  %trunc1 = trunc i32 %0 to i8
+  switch i8 %trunc, label %common.ret [
+    i8 44, label %sw.bb
+    i8 0, label %if.end.i.i2285
+  ]
+
+sw.bb:                                            ; preds = %cond.true20
+  %10 = load float, float* null, align 4
+  %11 = load float, float* null, align 4
+  %12 = tail call float @llvm.amdgcn.fmed3.f32(float %1, float 0.000000e+00, float 0.000000e+00)
+  %mul802 = fmul nsz float %1, 0.000000e+00
+  %cmp412.old3 = fcmp nsz ogt float %1, 0.000000e+00
+  br i1 %cmp412.old, label %if.then413, label %common.ret
+
+if.then413:                                       ; preds = %sw.bb
+  %13 = load <4 x i32>, <4 x i32> addrspace(1)* null, align 16
+  %14 = extractelement <4 x i32> %node, i64 0
+  %cmp4404 = fcmp nsz ole float %1, 0.000000e+00
+  %cmp4425 = icmp eq i32 %0, 0
+  %or.cond13066 = select i1 %cmp412.old, i1 false, i1 %cmp412.old
+  br i1 %or.cond1306, label %if.then443, label %if.else568
+
+if.then443:                                       ; preds = %if.then413
+  br i1 true, label %if.end511, label %common.ret
+
+common.ret.critedge:                              ; preds = %entry
+  store i32 0, i32* null, align 4
+  br label %common.ret
+
+common.ret:                                       ; preds = %if.end.i.i2285, %if.end627.sink.split, %cond.end579, %bsdf_alloc.exit2188, %if.end511, %common.ret.critedge, %if.then443, %sw.bb, %cond.true20, %cond.true
+  ret void
+
+if.end511:                                        ; preds = %if.then443
+  br i1 false, label %common.ret, label %if.then519
+
+if.then519:                                       ; preds = %if.end511
+  br i1 false, label %bsdf_alloc.exit2188, label %if.then.i2172
+
+if.then.i2172:                                    ; preds = %if.then519
+  br i1 false, label %closure_alloc.exit.i2184, label %if.end.i.i2181
+
+if.end.i.i2181:                                   ; preds = %if.then.i2172
+  br label %closure_alloc.exit.i2184
+
+closure_alloc.exit.i2184:                         ; preds = %if.end.i.i2181, %if.then.i2172
+  br i1 false, label %bsdf_alloc.exit2188, label %if.end.i2186
+
+if.end.i2186:                                     ; preds = %closure_alloc.exit.i2184
+  br label %bsdf_alloc.exit2188
+
+bsdf_alloc.exit2188:                              ; preds = %if.end.i2186, %closure_alloc.exit.i2184, %if.then519
+  br i1 false, label %common.ret, label %if.then534
+
+if.then534:                                       ; preds = %bsdf_alloc.exit2188
+  %.op7 = fmul nsz float undef, 0.000000e+00
+  %mul558 = select i1 %cmp440, float 0.000000e+00, float %1
+  %15 = tail call float @llvm.amdgcn.fmed3.f32(float 0.000000e+00, float 0.000000e+00, float 0.000000e+00)
+  store float %mul558, float addrspace(1)* null, align 4
+  br label %if.end627.sink.split
+
+if.else568:                                       ; preds = %if.then413
+  br i1 undef, label %bsdf_alloc.exit2214, label %if.then.i2198
+
+if.then.i2198:                                    ; preds = %if.else568
+  br i1 undef, label %closure_alloc.exit.i2210, label %if.end.i.i2207
+
+if.end.i.i2207:                                   ; preds = %if.then.i2198
+  %arrayidx.i.i22028 = getelementptr inbounds %struct.ShaderData, %struct.ShaderData addrspace(1)* %sd, i64 0, i32 30, i64 undef
+  br label %closure_alloc.exit.i2210
+
+closure_alloc.exit.i2210:                         ; preds = %if.end.i.i2207, %if.then.i2198
+  %retval.0.i.i220899 = phi %struct.ShaderClosure addrspace(1)* [ %arrayidx.i.i2202, %if.end.i.i2207 ], [ null, %if.then.i2198 ]
+  br i1 false, label %bsdf_alloc.exit2214, label %if.end.i2212
+
+if.end.i2212:                                     ; preds = %closure_alloc.exit.i2210
+  br label %bsdf_alloc.exit2214
+
+bsdf_alloc.exit2214:                              ; preds = %if.end.i2212, %closure_alloc.exit.i2210, %if.else568
+  %retval.1.i22131010 = phi %struct.ShaderClosure addrspace(1)* [ %arrayidx.i.i2202, %if.end.i2212 ], [ null, %closure_alloc.exit.i2210 ], [ null, %if.else568 ]
+  %cmp57511 = icmp ne %struct.ShaderClosure addrspace(1)* %arrayidx.i.i2202, null
+  br i1 %cmp442, label %cond.true576, label %cond.end579
+
+cond.true576:                                     ; preds = %bsdf_alloc.exit2214
+  %num_closure_left.i221512 = getelementptr inbounds %struct.ShaderData, %struct.ShaderData addrspace(1)* %sd, i64 0, i32 25
+  %16 = load i32, i32 addrspace(1)* %num_closure_left.i2215, align 8
+  %cmp.i221613 = icmp slt i32 %0, 0
+  br i1 %cmp440, label %cond.end579, label %if.end.i2227
+
+if.end.i2227:                                     ; preds = %cond.true576
+  %sub5.i222114 = add nuw nsw i32 %0, 0
+  %17 = load i32, i32 addrspace(1)* null, align 4294967296
+  %idx.ext.i222315 = sext i32 %0 to i64
+  %add.ptr.i2224 = getelementptr inbounds %struct.ShaderData, %struct.ShaderData addrspace(1)* %sd, i64 0, i32 30, i64 %idx.ext.i2223
+  %idx.ext8.i22252724 = zext i32 %0 to i64
+  %add.ptr9.i2226 = getelementptr inbounds %struct.ShaderClosure, %struct.ShaderClosure addrspace(1)* %add.ptr.i2224, i64 %idx.ext8.i22252724
+  %phi.cast2731 = bitcast %struct.ShaderClosure addrspace(1)* %add.ptr9.i2226 to %struct.MicrofacetExtra addrspace(1)*
+  br label %cond.end579
+
+cond.end579:                                      ; preds = %if.end.i2227, %cond.true576, %bsdf_alloc.exit2214
+  %cond580 = phi %struct.MicrofacetExtra addrspace(1)* [ null, %bsdf_alloc.exit2214 ], [ %phi.cast2731, %if.end.i2227 ], [ null, %cond.true576 ]
+  %tobool583 = icmp ne %struct.MicrofacetExtra addrspace(1)* %cond580, null
+  %or.cond1308 = select i1 %cmp442, i1 %tobool583, i1 false
+  br i1 %or.cond1308, label %if.then584, label %common.ret
+
+if.then584:                                       ; preds = %cond.end579
+  store %struct.MicrofacetExtra addrspace(1)* null, %struct.MicrofacetExtra addrspace(1)* addrspace(1)* null, align 4294967296
+  br label %if.end627.sink.split
+
+if.end627.sink.split:                             ; preds = %if.then584, %if.then534
+  store i32 0, i32 addrspace(1)* null, align 4
+  br label %common.ret
+
+if.end.i.i2285:                                   ; preds = %cond.true20
+  store i32 0, i32 addrspace(1)* null, align 4294967296
+  br label %common.ret
+}
+
+define internal fastcc void @svm_eval_nodes(%struct.ShaderData addrspace(1)* %sd) {
+sw.bb10:
+; GCN-LABEL: {{^}}svm_eval_nodes:
+; GCN-DAG: v_writelane_b32 [[CSR_VGPR:v[0-9]+]], s30,
+; GCN-DAG: v_writelane_b32 [[CSR_VGPR]], s31,
+; GCN: s_swappc_b64 s[30:31]
+; GCN-DAG: v_readlane_b32 s4, [[CSR_VGPR]],
+; GCN-DAG: v_readlane_b32 s5, [[CSR_VGPR]],
+; GCN: s_waitcnt vmcnt(0)
+; GCN: s_setpc_b64 s[4:5]
+  call fastcc void @svm_node_closure_bsdf(%struct.ShaderData addrspace(1)* null, float* null, <4 x i32> zeroinitializer, i32* null, i32 undef, i8 undef, float undef, float undef, float undef, i1 undef, <4 x i32> undef, float undef, i32 undef, i1 undef, i1 undef, i1 undef, float undef, %struct.ShaderClosure addrspace(1)* undef, %struct.ShaderClosure addrspace(1)* undef, %struct.ShaderClosure addrspace(1)* undef, i1 undef, i32 addrspace(1)* undef, i32 undef, i1 undef, i32 undef, i64 undef, i32 undef)
+  ret void
+}
+
+define amdgpu_kernel void @kernel_ocl_path_trace_shadow_blocked_dl() {
+kernel_set_buffer_pointers.exit:
+; GCN-LABEL: {{^}}kernel_ocl_path_trace_shadow_blocked_dl:
+; GCN: s_swappc_b64 s[30:31]
+; GCN: endpgm
+  tail call fastcc void @svm_eval_nodes(%struct.ShaderData addrspace(1)* null)
+  ret void
+}
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare float @llvm.fabs.f32(float) #0
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare float @llvm.maxnum.f32(float, float) #0
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare float @llvm.amdgcn.fmed3.f32(float, float, float) #3
+
+attributes #0 = { nofree nosync nounwind readnone speculatable willreturn }
+attributes #1 = { argmemonly nofree nosync nounwind willreturn }
+attributes #2 = { norecurse }
+attributes #3 = { nounwind readnone speculatable willreturn }