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

[Dawid Jurczak via Phabricator via llvm-commits]

yurai007 updated this revision to Diff 338373.
yurai007 removed rG LLVM Github Monorepo as the repository for this revision.

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

https://reviews.llvm.org/D100724

Files:
  llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
  llvm/test/Transforms/InstCombine/printf-2.ll


Index: llvm/test/Transforms/InstCombine/printf-2.ll
===================================================================
--- llvm/test/Transforms/InstCombine/printf-2.ll
+++ llvm/test/Transforms/InstCombine/printf-2.ll
@@ -56,3 +56,14 @@
   call void (i8*, ...) @printf(i8* %fmt, i8* %str)
   ret void
 }
+
+define void @test_simplify8() {
+; CHECK-LABEL: @test_simplify8(
+; CHECK-NEXT:    [[PUTS:%.*]] = call i32 @puts(i8* nonnull dereferenceable(1) getelementptr inbounds ([12 x i8], [12 x i8]* @str.1, i32 0, i32 0))
+; CHECK-NEXT:    ret void
+;
+  %fmt = getelementptr [3 x i8], [3 x i8]* @format_str, i32 0, i32 0
+  %str = getelementptr [13 x i8], [13 x i8]* @hello_world, i32 0, i32 0
+  call void (i8*, ...) @printf(i8* %fmt, i8* %str)
+  ret void
+}
Index: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2375,18 +2375,26 @@
   if (FormatStr.size() == 1 || FormatStr == "%%")
     return emitPutChar(B.getInt32(FormatStr[0]), B, TLI);
 
-  // printf("%s", "a") --> putchar('a')
+  // Try to emit putchar or puts.
   if (FormatStr == "%s" && CI->getNumArgOperands() > 1) {
-    StringRef ChrStr;
-    if (!getConstantStringInfo(CI->getOperand(1), ChrStr))
+    StringRef OperandStr;
+    if (!getConstantStringInfo(CI->getOperand(1), OperandStr) ||
+        OperandStr.empty())
       return nullptr;
-    if (ChrStr.size() != 1)
-      return nullptr;
-    return emitPutChar(B.getInt32(ChrStr[0]), B, TLI);
+    // printf("%s", "a") --> putchar('a')
+    if (OperandStr.size() == 1)
+      return emitPutChar(B.getInt32(OperandStr[0]), B, TLI);
+    // printf("%s", str"\n") --> puts(str)
+    else if (OperandStr.back() == '\n') {
+      OperandStr = OperandStr.drop_back();
+      Value *GV = B.CreateGlobalString(OperandStr, "str");
+      return emitPutS(GV, B, TLI);
+    }
+    return nullptr;
   }
 
   // printf("foo\n") --> puts("foo")
-  if (FormatStr[FormatStr.size() - 1] == '\n' &&
+  if (FormatStr.back() == '\n' &&
       FormatStr.find('%') == StringRef::npos) { // No format characters.
     // Create a string literal with no \n on it.  We expect the constant merge
     // pass to be run after this pass, to merge duplicate strings.


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