[AMDGPU] Add missing physical register check in SIFoldOperands::tryFoldLoad

[yassingh]

Summary

tryFoldLoad() is not meant to work on physical registers moreover
use_nodbg_instructions(reg) makes the compiler buggy when called with
physical reg

Fix for SWDEV-373493

[arsenm]

Could also use mir test

llvm/test/CodeGen/AMDGPU/swdev373493.ll

2

Don’t need -O3 and does need checks

8

Avoid branch on undef

31

Can drop attributes and metadata

[yassingh]

Addressed Matt's comments

[yassingh]

llvm/test/CodeGen/AMDGPU/swdev373493.ll

8

I generated this test by reducing the huge test filed with the ticket. I'm unable to generate the compiler failure without undef here.

[arsenm]

llvm/test/CodeGen/AMDGPU/swdev373493.ll

5

opt -passes=metarenamer?

llvm/test/CodeGen/AMDGPU/swdev373493.mir

2 ↗

(On Diff #490092)

This can be reduced, you can try llvm-reduce mir handling

[yassingh]

Addressed review comments, updated MIR test

[arsenm]

llvm/test/CodeGen/AMDGPU/fold-vgpr-phyreg.mir

27–35

If you use -run-pass=none, it will clean up and compact these register numbers for you

[yassingh]

Cleaned up MIR test

llvm/lib/Target/AMDGPU/SIFoldOperands.cpp

if (Users.empty())
     return false;
 
   // Check that all uses a copy to an agpr or a reg_sequence producing an agpr.
   while (!Users.empty()) {
     const MachineInstr *I = Users.pop_back_val();
     if (!I->isCopy() && !I->isRegSequence())
       return false;
     Register DstReg = I->getOperand(0).getReg();
+    // Physical registers may have more than one instruction definitions
+    if (DstReg.isPhysical())
+      return false;
     if (TRI->isAGPR(*MRI, DstReg))
       continue;
     MoveRegs.push_back(DstReg);
     for (const MachineInstr &U : MRI->use_nodbg_instructions(DstReg))
       Users.push_back(&U);
   }
 
   const TargetRegisterClass *RC = MRI->getRegClass(DefReg);

llvm/test/CodeGen/AMDGPU/fold-vgpr-phyreg.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -o - %s -mtriple=amdgcn-amd-amdhsa -mcpu=gfx90a -run-pass=si-fold-operands -verify-machineinstrs | FileCheck %s
+
+---
+name:            lshl_add_u64_gep
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0, $vgpr1, $vgpr2, $vgpr3
+
+    ; CHECK-LABEL: name: lshl_add_u64_gep
+    ; CHECK: liveins: $vgpr0, $vgpr1, $vgpr2, $vgpr3
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:vgpr_32 = COPY $vgpr3
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:vgpr_32 = COPY $vgpr2
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:vgpr_32 = COPY $vgpr1
+    ; CHECK-NEXT: [[COPY3:%[0-9]+]]:vgpr_32 = COPY $vgpr0
+    ; CHECK-NEXT: [[REG_SEQUENCE:%[0-9]+]]:vreg_64_align2 = REG_SEQUENCE [[COPY1]], %subreg.sub0, [[COPY]], %subreg.sub1
+    ; CHECK-NEXT: [[V_LSHLREV_B64_e64_:%[0-9]+]]:vreg_64_align2 = V_LSHLREV_B64_e64 2, [[REG_SEQUENCE]], implicit $exec
+    ; CHECK-NEXT: [[V_ADD_CO_U32_e64_:%[0-9]+]]:vgpr_32, [[V_ADD_CO_U32_e64_1:%[0-9]+]]:sreg_64_xexec = V_ADD_CO_U32_e64 [[COPY3]], [[V_LSHLREV_B64_e64_]].sub0, 0, implicit $exec
+    ; CHECK-NEXT: [[V_ADDC_U32_e64_:%[0-9]+]]:vgpr_32, dead [[V_ADDC_U32_e64_1:%[0-9]+]]:sreg_64_xexec = V_ADDC_U32_e64 [[COPY2]], [[V_LSHLREV_B64_e64_]].sub1, killed [[V_ADD_CO_U32_e64_1]], 0, implicit $exec
+    ; CHECK-NEXT: [[REG_SEQUENCE1:%[0-9]+]]:vreg_64_align2 = REG_SEQUENCE [[V_ADD_CO_U32_e64_]], %subreg.sub0, [[V_ADDC_U32_e64_]], %subreg.sub1
+    ; CHECK-NEXT: [[FLAT_LOAD_DWORD:%[0-9]+]]:vgpr_32 = FLAT_LOAD_DWORD killed [[REG_SEQUENCE1]], 0, 0, implicit $exec, implicit $flat_scr
+    ; CHECK-NEXT: $vgpr0 = COPY [[FLAT_LOAD_DWORD]]
+    ; CHECK-NEXT: SI_RETURN implicit $vgpr0
+    %0:vgpr_32 = COPY $vgpr3
+    %1:vgpr_32 = COPY $vgpr2
+    %2:vgpr_32 = COPY $vgpr1
+    %3:vgpr_32 = COPY $vgpr0
+    %4:vreg_64_align2 = REG_SEQUENCE %1, %subreg.sub0, %0, %subreg.sub1
+    %5:sreg_32 = S_MOV_B32 2
+    %6:vreg_64_align2 = V_LSHLREV_B64_e64 killed %5, %4, implicit $exec
+    %7:vgpr_32 = COPY %3
+    %8:vgpr_32 = COPY %6.sub0
+    %9:vgpr_32 = COPY %2
+    %10:vgpr_32 = COPY %6.sub1
+    %11:vgpr_32, %12:sreg_64_xexec = V_ADD_CO_U32_e64 %7, %8, 0, implicit $exec
+    %13:vgpr_32, dead %14:sreg_64_xexec = V_ADDC_U32_e64 %9, %10, killed %12, 0, implicit $exec
+    %15:vreg_64_align2 = REG_SEQUENCE %11, %subreg.sub0, %13, %subreg.sub1
+    %16:vgpr_32 = FLAT_LOAD_DWORD killed %15, 0, 0, implicit $exec, implicit $flat_scr
+    $vgpr0 = COPY %16
+    SI_RETURN implicit $vgpr0
+
+...

llvm/test/CodeGen/AMDGPU/swdev373493.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -o - %s -mtriple=amdgcn-amd-amdhsa -mcpu=gfx90a -verify-machineinstrs | FileCheck %s
+
+@global = external protected addrspace(4) externally_initialized global [4096 x i64], align 16
+
+define hidden fastcc void @bar(i32 %arg, ptr %arg1, ptr %arg2, ptr %arg3, ptr %arg4, ptr %arg5, ptr %arg6) unnamed_addr align 2 {
+; CHECK-LABEL: bar:
+; CHECK:       ; %bb.0: ; %bb
+; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; CHECK-NEXT:    v_mov_b32_e32 v15, v12
+; CHECK-NEXT:    v_mov_b32_e32 v14, v11
+; CHECK-NEXT:    v_mov_b32_e32 v13, v10
+; CHECK-NEXT:    v_mov_b32_e32 v12, v9
+; CHECK-NEXT:    v_mov_b32_e32 v11, v8
+; CHECK-NEXT:    v_mov_b32_e32 v10, v7
+; CHECK-NEXT:    v_mov_b32_e32 v9, v6
+; CHECK-NEXT:    v_mov_b32_e32 v8, v5
+; CHECK-NEXT:    v_mov_b32_e32 v7, v4
+; CHECK-NEXT:    v_mov_b32_e32 v6, v3
+; CHECK-NEXT:    s_cmp_lt_i32 s4, 3
+; CHECK-NEXT:    s_cbranch_scc0 .LBB0_3
+; CHECK-NEXT:  ; %bb.1: ; %LeafBlock
+; CHECK-NEXT:    s_cbranch_scc1 .LBB0_5
+; CHECK-NEXT:  ; %bb.2: ; %bb7
+; CHECK-NEXT:    flat_load_dwordx2 v[2:3], v[0:1]
+; CHECK-NEXT:    s_getpc_b64 s[16:17]
+; CHECK-NEXT:    s_add_u32 s16, s16, global@rel32@lo+1948
+; CHECK-NEXT:    s_addc_u32 s17, s17, global@rel32@hi+1956
+; CHECK-NEXT:    v_mov_b32_e32 v5, 0
+; CHECK-NEXT:    v_mov_b32_e32 v0, s16
+; CHECK-NEXT:    v_mov_b32_e32 v1, s17
+; CHECK-NEXT:    s_getpc_b64 s[18:19]
+; CHECK-NEXT:    s_add_u32 s18, s18, eggs@rel32@lo+4
+; CHECK-NEXT:    s_addc_u32 s19, s19, eggs@rel32@hi+12
+; CHECK-NEXT:    s_setpc_b64 s[18:19]
+; CHECK-NEXT:  .LBB0_3: ; %LeafBlock1
+; CHECK-NEXT:    s_cbranch_scc0 .LBB0_5
+; CHECK-NEXT:  ; %bb.4: ; %bb8
+; CHECK-NEXT:    v_mov_b32_e32 v0, v1
+; CHECK-NEXT:    v_mov_b32_e32 v1, v2
+; CHECK-NEXT:    v_mov_b32_e32 v2, v6
+; CHECK-NEXT:    v_mov_b32_e32 v3, v7
+; CHECK-NEXT:    v_mov_b32_e32 v4, v8
+; CHECK-NEXT:    v_mov_b32_e32 v5, v9
+; CHECK-NEXT:    v_mov_b32_e32 v6, v10
+; CHECK-NEXT:    v_mov_b32_e32 v7, v11
+; CHECK-NEXT:    v_mov_b32_e32 v8, v12
+; CHECK-NEXT:    v_mov_b32_e32 v9, v13
+; CHECK-NEXT:    v_mov_b32_e32 v10, v14
+; CHECK-NEXT:    v_mov_b32_e32 v11, v15
+; CHECK-NEXT:    s_getpc_b64 s[16:17]
+; CHECK-NEXT:    s_add_u32 s16, s16, quux@rel32@lo+4
+; CHECK-NEXT:    s_addc_u32 s17, s17, quux@rel32@hi+12
+; CHECK-NEXT:    s_setpc_b64 s[16:17]
+; CHECK-NEXT:  .LBB0_5: ; %bb9
+; CHECK-NEXT:    s_setpc_b64 s[30:31]
+bb:
+  switch i32 undef, label %bb9 [
+    i32 3, label %bb8
+    i32 1, label %bb7
+  ]
+
+bb7:                                              ; preds = %bb
+  %tmp = load ptr, ptr undef, align 8
+  tail call fastcc void @eggs(ptr noundef addrspacecast (ptr addrspace(4) getelementptr inbounds ([4096 x i64], ptr addrspace(4) @global, i64 0, i64 243) to ptr), ptr %tmp, ptr undef, ptr noundef nonnull align 8 dereferenceable(24) %arg2, ptr noundef %arg3, ptr noundef %arg4, ptr noundef %arg5)
+  br label %bb9
+
+bb8:                                              ; preds = %bb
+  tail call fastcc void @quux(ptr noundef nonnull align 8 dereferenceable(24) %arg1, ptr noundef nonnull align 8 dereferenceable(24) %arg2, ptr noundef %arg3, ptr noundef %arg4, ptr noundef %arg5, ptr noundef nonnull align 8 dereferenceable(8) %arg6)
+  br label %bb9
+
+bb9:                                              ; preds = %bb8, %bb7, %bb
+  ret void
+}
+
+declare dso_local fastcc void @eggs(ptr, ptr, ptr, ptr, ptr, ptr, ptr) unnamed_addr align 2
+
+declare dso_local fastcc void @quux(ptr, ptr, ptr, ptr, ptr, ptr) unnamed_addr align 2