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[v2,01/10] decodetree: Fix codegen for non-overlapping group inside overlapping group

Message ID 20201019151301.2046-2-peter.maydell@linaro.org
State New
Headers show
Series target/arm: Various v8.1M minor features | expand

Commit Message

Peter Maydell Oct. 19, 2020, 3:12 p.m. UTC 
For nested groups like:

  {
    [
      pattern 1
      pattern 2
    ]
    pattern 3
  }

the intended behaviour is that patterns 1 and 2 must not
overlap with each other; if the insn matches neither then
we fall through to pattern 3 as the next thing in the
outer overlapping group.

Currently we generate incorrect code for this situation,
because in the code path for a failed match inside the
inner non-overlapping group we generate a "return" statement,
which causes decode to stop entirely rather than continuing
to the next thing in the outer group.

Generate a "break" instead, so that decode flow behaves
as required for this nested group case.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 scripts/decodetree.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/scripts/decodetree.py b/scripts/decodetree.py
index 60fd3b5e5f6..c1bf3cfa85f 100644
--- a/scripts/decodetree.py
+++ b/scripts/decodetree.py
@@ -548,7 +548,7 @@  class Tree:
             output(ind, '    /* ',
                    str_match_bits(innerbits, innermask), ' */\n')
             s.output_code(i + 4, extracted, innerbits, innermask)
-            output(ind, '    return false;\n')
+            output(ind, '    break;\n')
         output(ind, '}\n')
 # end Tree