[llvm] 491beae - [TwoAddressInstruction] Update LiveIntervals after rewriting INSERT_SUBREG to COPY

[Jay Foad via llvm-commits]

Author: Jay Foad
Date: 2021-11-11T12:24:59Z
New Revision: 491beae71d69960a3bb0298b17d4ef1f3119b767

URL: https://github.com/llvm/llvm-project/commit/491beae71d69960a3bb0298b17d4ef1f3119b767
DIFF: https://github.com/llvm/llvm-project/commit/491beae71d69960a3bb0298b17d4ef1f3119b767.diff

LOG: [TwoAddressInstruction] Update LiveIntervals after rewriting INSERT_SUBREG to COPY

Also add subranges to an existing live interval when introducing a new
subreg def.

Differential Revision: https://reviews.llvm.org/D113044

Added: 
    

Modified: 
    llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
    llvm/test/CodeGen/AMDGPU/undefined-subreg-liverange.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 9c9636c49dfc..6673de548de1 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1757,6 +1757,34 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
         mi->RemoveOperand(1);
         mi->setDesc(TII->get(TargetOpcode::COPY));
         LLVM_DEBUG(dbgs() << "\t\tconvert to:\t" << *mi);
+
+        // Update LiveIntervals.
+        if (LIS) {
+          Register Reg = mi->getOperand(0).getReg();
+          LiveInterval &LI = LIS->getInterval(Reg);
+          if (LI.hasSubRanges()) {
+            // The COPY no longer defines subregs of %reg except for
+            // %reg.subidx.
+            LaneBitmask LaneMask =
+                TRI->getSubRegIndexLaneMask(mi->getOperand(0).getSubReg());
+            SlotIndex Idx = LIS->getInstructionIndex(*mi);
+            for (auto &S : LI.subranges()) {
+              if ((S.LaneMask & LaneMask).none()) {
+                LiveRange::iterator UseSeg = S.FindSegmentContaining(Idx);
+                LiveRange::iterator DefSeg = std::next(UseSeg);
+                S.MergeValueNumberInto(DefSeg->valno, UseSeg->valno);
+              }
+            }
+
+            // The COPY no longer has a use of %reg.
+            LIS->shrinkToUses(&LI);
+          } else {
+            // The live interval for Reg did not have subranges but now it needs
+            // them because we have introduced a subreg def. Recompute it.
+            LIS->removeInterval(Reg);
+            LIS->createAndComputeVirtRegInterval(Reg);
+          }
+        }
       }
 
       // Clear TiedOperands here instead of at the top of the loop

diff  --git a/llvm/test/CodeGen/AMDGPU/undefined-subreg-liverange.ll b/llvm/test/CodeGen/AMDGPU/undefined-subreg-liverange.ll
index 7408688bb23f..994abf9bb750 100644
--- a/llvm/test/CodeGen/AMDGPU/undefined-subreg-liverange.ll
+++ b/llvm/test/CodeGen/AMDGPU/undefined-subreg-liverange.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck %s
+; RUN: llc -march=amdgcn -verify-machineinstrs -early-live-intervals < %s | FileCheck %s
 
 ; We may have subregister live ranges that are undefined on some paths. The
 ; verifier should not complain about this.