[PATCH] D111317: [DebugInfo][InstrRef] Track instructions that write-to-stack after having a spill fused into them

Mon Oct 25 04:19:01 PDT 2021

jmorse added inline comments.

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Comment at: llvm/test/DebugInfo/MIR/InstrRef/memory-operand-tracking.mir:54-57
+    ;; We should _not_ be able to find the old value.
+    DBG_INSTR_REF 1, 0, !11, !DIExpression(), debug-location !12
+    ; CHECK:      DBG_INSTR_REF 1, 0
+    ; CHECK-NEXT: DBG_VALUE $noreg
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Orlando wrote:
> What is the purpose of this part of the test?
It's testing that the old value, `DBG_PHI $rax, 1`, can't be found anywhere. It's moderately important as the INC32m's write to the stack should terminate any earlier values being tracked.

Thinking about it, this test should also check that variables _currently_ located on the stack get terminated if it's overwritten, i.e.:

  SOMEINST debug-instr-number 1 ::(store 8 into %stack.0)
  DBG_INSTR_REF 1, 1000000
  OTHERINST ::(store 8 into %stack.0)

needs an explicit DBG_VALUE $noreg after OTHERINST overwrites the stack locataion. DbgEntityHistoryCalculator isn't aware of memory stores.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111317/new/

https://reviews.llvm.org/D111317