[AMDGPU] Fix kill flag on overlapping sgpr copy

[sebastian-ne]

Summary

Same as on vgpr copies, we cannot kill the source register if it
overlaps with the destination register. Otherwise, the kill of the
source register will also count as a kill for the destination register.

[foad]

LGTM, thanks!

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

void SIInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
   }
 
   const bool Forward = RI.getHWRegIndex(DestReg) <= RI.getHWRegIndex(SrcReg);
   if (RI.isSGPRClass(RC)) {
     if (!RI.isSGPRClass(SrcRC)) {
       reportIllegalCopy(this, MBB, MI, DL, DestReg, SrcReg, KillSrc);
       return;
     }
-    expandSGPRCopy(*this, MBB, MI, DL, DestReg, SrcReg, KillSrc, RC, Forward);
+    const bool CanKillSuperReg = KillSrc && !RI.regsOverlap(SrcReg, DestReg);
+    expandSGPRCopy(*this, MBB, MI, DL, DestReg, SrcReg, CanKillSuperReg, RC,
+                   Forward);
     return;
   }
 
   unsigned EltSize = 4;
   unsigned Opcode = AMDGPU::V_MOV_B32_e32;
   if (RI.isAGPRClass(RC)) {
     if (ST.hasGFX90AInsts() && RI.isAGPRClass(SrcRC))
       Opcode = AMDGPU::V_ACCVGPR_MOV_B32;

llvm/test/CodeGen/AMDGPU/copy-overlap-sgpr-kill.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx906 -verify-machineinstrs -run-pass=postrapseudos -o - %s | FileCheck %s
+
+# Don't set a kill of the super register on the last instruction with
+# an overlapping copy. This would kill part of the values in the
+# result copies.
+
+---
+name: overlapping_copy_kill_undef_reg_after_copy
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $sgpr30_sgpr31, $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+
+    ; CHECK-LABEL: name: overlapping_copy_kill_undef_reg_after_copy
+    ; CHECK: liveins: $sgpr30_sgpr31, $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: $sgpr0_sgpr1 = S_MOV_B64 $sgpr4_sgpr5, implicit $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11, implicit-def $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7
+    ; CHECK-NEXT: $sgpr2_sgpr3 = S_MOV_B64 $sgpr6_sgpr7, implicit $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+    ; CHECK-NEXT: $sgpr4_sgpr5 = S_MOV_B64 $sgpr8_sgpr9, implicit $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+    ; CHECK-NEXT: $sgpr6_sgpr7 = S_MOV_B64 $sgpr10_sgpr11, implicit $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+    ; CHECK-NEXT: renamable $sgpr1 = S_ADD_I32 0, $sgpr1, implicit-def $scc
+    ; CHECK-NEXT: S_SETPC_B64 $sgpr30_sgpr31, implicit $sgpr0, implicit $sgpr1, implicit $sgpr2, implicit $sgpr3, implicit $sgpr4, implicit $sgpr5, implicit $sgpr6, implicit $sgpr7
+    renamable $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7 = COPY killed renamable $sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11
+    renamable $sgpr1 = S_ADD_I32 0, $sgpr1, implicit-def $scc
+    S_SETPC_B64 $sgpr30_sgpr31, implicit $sgpr0, implicit $sgpr1, implicit $sgpr2, implicit $sgpr3, implicit $sgpr4, implicit $sgpr5, implicit $sgpr6, implicit $sgpr7
+
+...
+
+---
+name: nonoverlapping_copy_kill
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $sgpr30_sgpr31, $sgpr3_sgpr4_sgpr5
+
+    ; CHECK-LABEL: name: nonoverlapping_copy_kill
+    ; CHECK: liveins: $sgpr30_sgpr31, $sgpr3_sgpr4_sgpr5
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: $sgpr0 = S_MOV_B32 $sgpr3, implicit $sgpr3_sgpr4_sgpr5, implicit-def $sgpr0_sgpr1_sgpr2
+    ; CHECK-NEXT: $sgpr1 = S_MOV_B32 $sgpr4, implicit $sgpr3_sgpr4_sgpr5
+    ; CHECK-NEXT: $sgpr2 = S_MOV_B32 $sgpr5, implicit killed $sgpr3_sgpr4_sgpr5
+    ; CHECK-NEXT: renamable $sgpr1 = S_ADD_I32 0, $sgpr1, implicit-def $scc
+    ; CHECK-NEXT: S_SETPC_B64 $sgpr30_sgpr31, implicit $sgpr0, implicit $sgpr1, implicit $sgpr2
+    renamable $sgpr0_sgpr1_sgpr2 = COPY killed renamable $sgpr3_sgpr4_sgpr5
+    renamable $sgpr1 = S_ADD_I32 0, $sgpr1, implicit-def $scc
+    S_SETPC_B64 $sgpr30_sgpr31, implicit $sgpr0, implicit $sgpr1, implicit $sgpr2
+
+...