Fix #3170: Allow coalescing of the same node during register allocation.

  The x86 code generator sometimes generates nop moves like
  movl %vI_a %vI_a, but we'll just ignore them for coalescing
  purposes instead of emitting an error. It shouldn't hurt anything.
parent 5581ce52
......@@ -335,6 +335,9 @@ coalesceNodes aggressive triv graph (k1, k2)
, not $ elementOfUniqSet kMin (nodeConflicts nMax)
, not $ elementOfUniqSet kMax (nodeConflicts nMin)
-- can't coalesce the same node
, nodeId nMin /= nodeId nMax
= coalesceNodes_merge aggressive triv graph kMin kMax nMin nMax
-- don't do the coalescing after all
......@@ -350,9 +353,6 @@ coalesceNodes_merge aggressive triv graph kMin kMax nMin nMax
| not (isNothing (nodeColor nMin) && isNothing (nodeColor nMax))
= error "GraphOps.coalesceNodes: can't coalesce colored nodes."
| nodeId nMin == nodeId nMax
= error "GraphOps.coalesceNodes: can't coalesce the same node."
---
| otherwise
= let
......
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