[PATCH] D96418: [clang] Refactor mustprogress handling, add it to all loops in c++11+.

[Florian Hahn via Phabricator via cfe-commits]

fhahn added inline comments.


================
Comment at: clang/lib/CodeGen/CGStmt.cpp:801
+                 SourceLocToDebugLoc(R.getEnd()),
+                 loopMustProgress(CondIsConst));
 
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lebedev.ri wrote:
> fhahn wrote:
> > lebedev.ri wrote:
> > > Now this doesn't make sense. Why must loop progress if it's condition is a constant?
> > > I think this should be renamed?
> > I'm not sure I follow here. Whether the condition is constant or not is important for C11 and later. Something like ` while(true) {}` does not have to make progress, but `while (Foo) {}` must make progress. I am not sure what it should be renamed to?
> Right.
> But now this says that "if the condition is a constant integer 1 or 0, the loop must make progress".
> Isn't that the opposite what this should say, as per your comment?
> Shouldn't it be "loop must progress unless the condition is a constant integer 1"?
Ok, so with 'saying' do you mean `loopMustProgress` is a bad name? I changed the name as suggested below, but if you meant something else, please let me know.


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Comment at: clang/lib/CodeGen/CodeGenFunction.h:535-536
+    // Hence each function is 'mustprogress' in C++11 or later.
     return getLangOpts().CPlusPlus11 || getLangOpts().CPlusPlus14 ||
            getLangOpts().CPlusPlus17 || getLangOpts().CPlusPlus20;
   }
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lebedev.ri wrote:
> Since every new standard version will have to be added here,
> can we invert this and just check for the know fixed set
> of the versions where this doesn't apply?
I tried, but it appears as if there's no LangOpt for `C++98`. (this also seems not directly related to the patch, so I guess we could do that as follow-up as well?)


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Comment at: clang/lib/CodeGen/CodeGenFunction.h:542
+  /// condition is a known constant.
+  bool loopMustProgress(bool HasConstantCond) {
     if (CGM.getCodeGenOpts().getFiniteLoops() ==
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lebedev.ri wrote:
> Ah, i see.
> My problem is that it's impossible to tell whether `loopMustProgress` is a member variable
> that gets assigned `CondIsConstInt` value, or a "filter" function.
> 
> Maybe this (and it's `function` friend) should be something like `checkIfLoopMustProgress` or something..
Oh right, the name was confusing. I updated the name


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Comment at: clang/lib/CodeGen/CodeGenFunction.h:562
+    // Loops with non-constant conditions must make progress in C11 and later.
+    return getLangOpts().C11 || getLangOpts().C17 || getLangOpts().C2x;
   }
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lebedev.ri wrote:
> Since every new standard version will have to be added here,
> can we invert this and just check for the know fixed set
> of the versions where this doesn't apply?
I tried but I am not sure how to best do that, given there's no explicit C89 lang opt.


Repository:
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  https://reviews.llvm.org/D96418/new/

https://reviews.llvm.org/D96418