[PATCH] D100724: [SimplifyLibCalls] Transform printf("%s", str"\n") --> puts(str).

[Dawid Jurczak via Phabricator via llvm-commits]

yurai007 added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2382
+    if (!getConstantStringInfo(CI->getOperand(1), OperandStr) ||
+        OperandStr.empty())
       return nullptr;
----------------
spatel wrote:
> What does it mean if the operand string is empty?
>   printf("%s", "");
> 
> It can be another patch, but please leave a "TODO" comment. Looks like gcc removes the call entirely.
Ok, will add it to this patch if you don't mind.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2383
+        OperandStr.empty())
       return nullptr;
+    // printf("%s", "a") --> putchar('a')
----------------
xbolva00 wrote:
> We could even handle printf("%s", "");
> 
> if (OperandStr.empty())
>     return ConstantInt::get(CI->getType(), 0);
> 
> https://godbolt.org/z/Ke5bcxWPK
Nice finding. I will include this optimization to patch.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D100724/new/

https://reviews.llvm.org/D100724