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diff extra/README @ 417:d7b7004b0883
Update gcc6809 patch to fix an ICE.
Add new gcc6809 patch with a fix to an internal compiler error reported by
Tormod Volden. It seems whoever created the offending instruction patterns
didn't fully understand the instruction contraints system and likely got
away with it due to characteristics of the instruction generator in previous
versions of gcc. Alas, it causes problems now so unless someone has a
brilliant idea how to make it work, addhi_mem_1 and addhi_mem_minus1 have to
go. Fortunately, the compiler is smart enough to use an alternate strategy
all on its own.
| author | William Astle <lost@l-w.ca> |
|---|---|
| date | Sun, 27 Mar 2016 21:46:18 -0600 |
| parents | b4d0eafc5bfe |
| children | 3832a68d83ef |
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--- a/extra/README Thu Mar 24 20:07:20 2016 -0600 +++ b/extra/README Sun Mar 27 21:46:18 2016 -0600 @@ -132,3 +132,15 @@ that showed up under optimization. It would result in the sense of a branch following a subtraction being inverted for whatever reason. This change seems to fix that. + +gcc6809lw-4.6.4-5.patch + +This is the same as the -4 version except it removes two instruction +patterns that gcc was choosing to use in cases where they simply did not +apply and, thus, it was getting confused and leading to an ICE. These +patterns were a useful optmization for incrementing and decrementing 16 bit +values in memory but if the compiler core is going to select them in cases +where it really isn't an increment or decrement in place, the patterns are +not useful. The resulting code is slightly less good than it could be under +-Os but it's still correct. +