[PATCH] D127115: [RFC][DAGCombine] Make sure combined nodes are added back to the worklist in topological order.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

@deadalnix please can you rebase against trunk?



================
Comment at: llvm/test/CodeGen/ARM/dsp-mlal.ll:39
+; NODSP-NEXT:    bx lr
 entry:
   %conv = sext i32 %b1 to i64
----------------
BEFORE:
```
SelectionDAG has 21 nodes:
  t0: ch = EntryToken
        t45: i32,i32 = uaddo t44, Constant:i32<-2147483648>
      t46: i32,i32 = addcarry t44:1, Constant:i32<0>, t45:1
      t49: i32,i32 = uaddo t41, Constant:i32<-2147483648>
    t52: i32,i32 = addcarry t41:1, t46, t49:1
  t29: ch,glue = CopyToReg t0, Register:i32 $r0, t52
    t8: i32,ch = CopyFromReg t0, Register:i32 %3
    t4: i32,ch = CopyFromReg t0, Register:i32 %1
  t41: i32,i32 = smul_lohi t8, t4
    t42: i32,ch = load<(load (s32) from %fixed-stack.0, align 8)> t0, FrameIndex:i32<-1>, undef:i32
    t6: i32,ch = CopyFromReg t0, Register:i32 %2
  t44: i32,i32 = smul_lohi t42, t6
  t30: ch = ARMISD::RET_FLAG t29, Register:i32 $r0, t29:1
```
AFTER:
```
SelectionDAG has 21 nodes:
  t0: ch = EntryToken
        t45: i32,i32 = uaddo t44, Constant:i32<-2147483648>
      t53: i32,i32 = addcarry t41:1, t44:1, t45:1
      t49: i32,i32 = uaddo t41, Constant:i32<-2147483648>
    t50: i32,i32 = addcarry t53, Constant:i32<0>, t49:1
  t29: ch,glue = CopyToReg t0, Register:i32 $r0, t50
    t8: i32,ch = CopyFromReg t0, Register:i32 %3
    t4: i32,ch = CopyFromReg t0, Register:i32 %1
  t41: i32,i32 = smul_lohi t8, t4
    t42: i32,ch = load<(load (s32) from %fixed-stack.0, align 8)> t0, FrameIndex:i32<-1>, undef:i32
    t6: i32,ch = CopyFromReg t0, Register:i32 %2
  t44: i32,i32 = smul_lohi t42, t6
  t30: ch = ARMISD::RET_FLAG t29, Register:i32 $r0, t29:1
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D127115/new/

https://reviews.llvm.org/D127115