[PATCH] D60887: [AsmPrinter] refactor to support %c w/ GlobalAddress'

Wed Apr 24 16:22:39 PDT 2019

nickdesaulniers marked an inline comment as done.
nickdesaulniers added inline comments.

================
Comment at: llvm/lib/Target/MSP430/MSP430AsmPrinter.cpp:101
+    O << '#';
+    PrintSymbolOperand(MO, O);
     return;
----------------
nickdesaulniers wrote:
> peter.smith wrote:
> > This looks to have taken out the case when isMemOp is true (the removed code could output &). I don't know enough about MSP430 to know whether this is the right thing to do though.
> The conditional in the initialization of `isMemOp` and the condition I removed here are quite tricky and require careful attention.
> 
> The unconditional printing of `'#'` comes from the observation in the previous version of the code that:
> 1. there is no such modifier `"mem"` ever
> 2. thus `strcmp` will always be non-zero
> 3. thus `!strcmp` will always be `0`
> 4. thus `Modifier && !strcmp` will always be `false`
> 5. thus `isMemOp` will always be `false`
> 6. thus `(isMemOp ? '&' : '#')` will always evaluate to `'#'`
> 
> The next transform is based on the above AND the observations:
> 1. the only modifier is "nohash"
> 2. thus if there is no `Modifier`, print `'#'`
> 3. or if the only possible modifier is the only possible value, print `'#'`
> 4. thus what we have is an unconditional print of `'#'`
> 
> But I will admit this was tricky when first looking at it and would appreciate you triple checking as I may have made a mistake in the above logic.  It's definitely the most curious part of this patch for sure.  Also, sorry if I misunderstood your point. Thanks for your review!
Also, I had previously tackled this in https://reviews.llvm.org/D60738, but abandoned it when I started the overall fix, as I needed it one way or another.  Happy to revive that there, land it first, then rebase this if you prefer?

Repository:
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  https://reviews.llvm.org/D60887/new/

https://reviews.llvm.org/D60887