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

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2379
+  // Try to emit putchar or puts.
   if (FormatStr == "%s" && CI->getNumArgOperands() > 1) {
+    StringRef OperandStr;
----------------
Why is this checking for `args > 1` instead of exactly `args == 2`?


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2382
+    if (!getConstantStringInfo(CI->getOperand(1), OperandStr) ||
+        OperandStr.empty())
       return nullptr;
----------------
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.


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2388
+    // printf("%s", str"\n") --> puts(str)
+    else if (OperandStr.back() == '\n') {
+      OperandStr = OperandStr.drop_back();
----------------
Style: remove `else` ( https://llvm.org/docs/CodingStandards.html#don-t-use-else-after-a-return )


================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:2397
   // printf("foo\n") --> puts("foo")
-  if (FormatStr[FormatStr.size() - 1] == '\n' &&
+  if (FormatStr.back() == '\n' &&
       FormatStr.find('%') == StringRef::npos) { // No format characters.
----------------
That diff is independent of this patch, so could be an NFC preliminary cleanup.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100724/new/

https://reviews.llvm.org/D100724