[SLC] sprintf(dst, "%s", str) -> strcpy(dst, str)

Solves 46489

Author: davidbolvansky

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -2487,21 +2487,11 @@ Value *LibCallSimplifier::optimizeSPrintFString(CallInst *CI,
   }
 
   if (FormatStr[1] == 's') {
-    // sprintf(dest, "%s", str) -> llvm.memcpy(align 1 dest, align 1 str,
-    // strlen(str)+1)
+    // sprintf(dest, "%s", str) -> strcpy(dest, str)
     if (!CI->getArgOperand(2)->getType()->isPointerTy())
       return nullptr;
 
-    Value *Len = emitStrLen(CI->getArgOperand(2), B, DL, TLI);
-    if (!Len)
-      return nullptr;
-    Value *IncLen =
-        B.CreateAdd(Len, ConstantInt::get(Len->getType(), 1), "leninc");
-    B.CreateMemCpy(CI->getArgOperand(0), Align(1), CI->getArgOperand(2),
-                   Align(1), IncLen);
-
-    // The sprintf result is the unincremented number of bytes in the string.
-    return B.CreateIntCast(Len, CI->getType(), false);
+    return emitStrCpy(CI->getArgOperand(0), CI->getArgOperand(2), B, TLI);
   }
   return nullptr;
 }

llvm/test/Transforms/InstCombine/2010-05-30-memcpy-Struct.ll

@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -instcombine -S < %s | FileCheck %s
 ; PR7265
 
@@ -9,10 +10,14 @@ target triple = "x86_64-unknown-linux-gnu"
 @.str = private constant [3 x i8] c"%s\00"
 
 define void @CopyEventArg(%union.anon* %ev) nounwind {
+; CHECK-LABEL: @CopyEventArg(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CSTR:%.*]] = bitcast %union.anon* [[EV:%.*]] to i8*
+; CHECK-NEXT:    [[STRCPY:%.*]] = call i8* @strcpy(i8* nonnull dereferenceable(1) undef, i8* nonnull dereferenceable(1) [[CSTR]])
+; CHECK-NEXT:    ret void
+;
 entry:
   %call = call i32 (i8*, i8*, ...) @sprintf(i8* undef, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), %union.anon* %ev) nounwind
-; CHECK: bitcast %union.anon* %ev to i8*
-; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64
   ret void
 }
 

llvm/test/Transforms/InstCombine/sprintf-1.ll

@@ -81,19 +81,15 @@ define void @test_simplify4(i8* %dst) {
   ret void
 }
 
-; Check sprintf(dst, "%s", str) -> llvm.memcpy(dest, str, strlen(str) + 1, 1).
+; Check sprintf(dst, "%s", str) -> strcpy(dst, str)
 
 define void @test_simplify5(i8* %dst, i8* %str) {
 ; CHECK-LABEL: @test_simplify5(
-; CHECK-NEXT:    [[STRLEN:%.*]] = call i32 @strlen(i8* nonnull dereferenceable(1) [[STR:%.*]])
-; CHECK-NEXT:    [[LENINC:%.*]] = add i32 [[STRLEN]], 1
-; CHECK-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 1 [[DST:%.*]], i8* align 1 [[STR]], i32 [[LENINC]], i1 false)
+; CHECK-NEXT:    [[STRCPY:%.*]] = call i8* @strcpy(i8* nonnull dereferenceable(1) [[DST:%.*]], i8* nonnull dereferenceable(1) [[STR:%.*]])
 ; CHECK-NEXT:    ret void
 ;
 ; CHECK-IPRINTF-LABEL: @test_simplify5(
-; CHECK-IPRINTF-NEXT:    [[STRLEN:%.*]] = call i32 @strlen(i8* nonnull dereferenceable(1) [[STR:%.*]])
-; CHECK-IPRINTF-NEXT:    [[LENINC:%.*]] = add i32 [[STRLEN]], 1
-; CHECK-IPRINTF-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 1 [[DST:%.*]], i8* align 1 [[STR]], i32 [[LENINC]], i1 false)
+; CHECK-IPRINTF-NEXT:    [[STRCPY:%.*]] = call i8* @strcpy(i8* nonnull dereferenceable(1) [[DST:%.*]], i8* nonnull dereferenceable(1) [[STR:%.*]])
 ; CHECK-IPRINTF-NEXT:    ret void
 ;
   %fmt = getelementptr [3 x i8], [3 x i8]* @percent_s, i32 0, i32 0