[SLC] Optimize mempcpy_chk to mempcpy

[xbolva00]

Summary

As reported in PR46735:

void* f(void *d, const void *s, size_t l)
{

return __builtin___mempcpy_chk(d, s, l, __builtin_object_size(d, 0));

}

This can be optimized to return mempcpy(d, s, l);.

[xbolva00]

llvm/test/Transforms/InstCombine/fortify-folding.ll

36

Well actually LLVM goes futher and transforms mempcpy to memcpy + dst, since we have more optimizations for memcpy.

[efriedma]

This patch has an obvious miscompile; please try to be more careful testing your patches.

[xbolva00]

Eh, copy paste error from memcpy.

I will fix it.

[xbolva00]

Fixed.

[xbolva00]

Updated.

Ping.

[xbolva00]

ping

[xbolva00]

ping

[xbolva00]

Ping @efriedma

[efriedma]

LGTM

[MaskRay]

(Minor nit: [SLC] is not obvious. SimplifyLibCalls may be better.)

llvm/include/llvm/Analysis/TargetLibraryInfo.def

 TLI_DEFINE_STRING_INTERNAL("__logf_finite")
 /// long double __logl_finite(long double x);
 TLI_DEFINE_ENUM_INTERNAL(logl_finite)
 TLI_DEFINE_STRING_INTERNAL("__logl_finite")
 /// void *__memccpy_chk(void *dst, const void *src, int c, size_t n,
 ///                     size_t dstsize)
 TLI_DEFINE_ENUM_INTERNAL(memccpy_chk)
 TLI_DEFINE_STRING_INTERNAL("__memccpy_chk")
+/// void *__mempcpy_chk(void *s1, const void *s2, size_t n, size_t s1size);
+TLI_DEFINE_ENUM_INTERNAL(mempcpy_chk)
+TLI_DEFINE_STRING_INTERNAL("__mempcpy_chk")
 /// void *__memcpy_chk(void *s1, const void *s2, size_t n, size_t s1size);
 TLI_DEFINE_ENUM_INTERNAL(memcpy_chk)
 TLI_DEFINE_STRING_INTERNAL("__memcpy_chk")
 /// void *__memmove_chk(void *s1, const void *s2, size_t n, size_t s1size);
 TLI_DEFINE_ENUM_INTERNAL(memmove_chk)
 TLI_DEFINE_STRING_INTERNAL("__memmove_chk")
 /// void *__memset_chk(void *s, char v, size_t n, size_t s1size);
 TLI_DEFINE_ENUM_INTERNAL(memset_chk)

llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h

private:
   Value *optimizeMemCpyChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeMemMoveChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeMemSetChk(CallInst *CI, IRBuilderBase &B);
 
   /// Str/Stp cpy are similar enough to be handled in the same functions.
   Value *optimizeStrpCpyChk(CallInst *CI, IRBuilderBase &B, LibFunc Func);
   Value *optimizeStrpNCpyChk(CallInst *CI, IRBuilderBase &B, LibFunc Func);
   Value *optimizeStrLenChk(CallInst *CI, IRBuilderBase &B);
+  Value *optimizeMemPCpyChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeMemCCpyChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeSNPrintfChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeSPrintfChk(CallInst *CI,IRBuilderBase &B);
   Value *optimizeStrCatChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeStrLCat(CallInst *CI, IRBuilderBase &B);
   Value *optimizeStrNCatChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeStrLCpyChk(CallInst *CI, IRBuilderBase &B);
   Value *optimizeVSNPrintfChk(CallInst *CI, IRBuilderBase &B);

llvm/lib/Analysis/TargetLibraryInfo.cpp

return (NumParams == 3 && FTy.getReturnType()->isPointerTy() &&
             FTy.getReturnType() == FTy.getParamType(0) &&
             FTy.getParamType(1)->isIntegerTy(32) &&
             IsSizeTTy(FTy.getParamType(2)));
   case LibFunc_modf:
   case LibFunc_modff:
   case LibFunc_modfl:
     return (NumParams >= 2 && FTy.getParamType(1)->isPointerTy());
 
+  case LibFunc_mempcpy_chk:
   case LibFunc_memcpy_chk:
   case LibFunc_memmove_chk:
     --NumParams;
     if (!IsSizeTTy(FTy.getParamType(NumParams)))
       return false;
     LLVM_FALLTHROUGH;
   case LibFunc_memcpy:
   case LibFunc_mempcpy:

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

Value *llvm::emitMemCpyChk(Value *Dst, Value *Src, Value *Len, Value *ObjSize,
   Src = castToCStr(Src, B);
   CallInst *CI = B.CreateCall(MemCpy, {Dst, Src, Len, ObjSize});
   if (const Function *F =
           dyn_cast<Function>(MemCpy.getCallee()->stripPointerCasts()))
     CI->setCallingConv(F->getCallingConv());
   return CI;
 }
 
+Value *llvm::emitMemPCpy(Value *Dst, Value *Src, Value *Len, IRBuilderBase &B,
+                         const DataLayout &DL, const TargetLibraryInfo *TLI) {
+  LLVMContext &Context = B.GetInsertBlock()->getContext();
+  return emitLibCall(
+      LibFunc_mempcpy, B.getInt8PtrTy(),
+      {B.getInt8PtrTy(), B.getInt8PtrTy(), DL.getIntPtrType(Context)},
+      {Dst, Src, Len}, B, TLI);
+}
+
 Value *llvm::emitMemChr(Value *Ptr, Value *Val, Value *Len, IRBuilderBase &B,
                         const DataLayout &DL, const TargetLibraryInfo *TLI) {
   LLVMContext &Context = B.GetInsertBlock()->getContext();
   return emitLibCall(
       LibFunc_memchr, B.getInt8PtrTy(),
       {B.getInt8PtrTy(), B.getInt32Ty(), DL.getIntPtrType(Context)},
       {castToCStr(Ptr, B), Val, Len}, B, TLI);
 }

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

if (isFortifiedCallFoldable(CI, 3, 2)) {
     CallInst *NewCI = B.CreateMemSet(CI->getArgOperand(0), Val,
                                      CI->getArgOperand(2), Align(1));
     NewCI->setAttributes(CI->getAttributes());
     return CI->getArgOperand(0);
   }
   return nullptr;
 }
 
+Value *FortifiedLibCallSimplifier::optimizeMemPCpyChk(CallInst *CI,
+                                                      IRBuilderBase &B) {
+  const DataLayout &DL = CI->getModule()->getDataLayout();
+  if (isFortifiedCallFoldable(CI, 3, 2)) {
+    CallInst *NewCI =
+        cast<CallInst>(emitMemPCpy(CI->getArgOperand(0), CI->getArgOperand(1),
+                                   CI->getArgOperand(2), B, DL, TLI));
+    NewCI->setAttributes(CI->getAttributes());
+    return CI->getArgOperand(0);
+  }
+  return nullptr;
+}
+
 Value *FortifiedLibCallSimplifier::optimizeStrpCpyChk(CallInst *CI,
                                                       IRBuilderBase &B,
                                                       LibFunc Func) {
   const DataLayout &DL = CI->getModule()->getDataLayout();
   Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1),
         *ObjSize = CI->getArgOperand(2);
 
   // __stpcpy_chk(x,x,...)  -> x+strlen(x)
Value *FortifiedLibCallSimplifier::optimizeCall(CallInst *CI,
 
   // We never change the calling convention.
   if (!ignoreCallingConv(Func) && !isCallingConvC)
     return nullptr;
 
   switch (Func) {
   case LibFunc_memcpy_chk:
     return optimizeMemCpyChk(CI, Builder);
+  case LibFunc_mempcpy_chk:
+    return optimizeMemPCpyChk(CI, Builder);
   case LibFunc_memmove_chk:
     return optimizeMemMoveChk(CI, Builder);
   case LibFunc_memset_chk:
     return optimizeMemSetChk(CI, Builder);
   case LibFunc_stpcpy_chk:
   case LibFunc_strcpy_chk:
     return optimizeStrpCpyChk(CI, Builder, Func);
   case LibFunc_strlen_chk:

llvm/test/Transforms/InstCombine/fortify-folding.ll

 ; CHECK-NEXT:    ret i8* [[RET]]
 ;
   %dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
   %src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
   %ret = call i8* @__memccpy_chk(i8* %dst, i8* %src, i32 0, i64 60, i64 59)
   ret i8* %ret
 }
 
+define i8* @test_mempcpy() {
+; CHECK-LABEL: @test_mempcpy(
+; CHECK-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 1 dereferenceable(60) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0), i8* nonnull align 1 dereferenceable(60) getelementptr inbounds ([60 x i8], [60 x i8]* @b, i64 0, i64 0), i64 60, i1 false)
+; CHECK-NEXT:    ret i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0)
+;
+  %dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
+  %src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
+  %ret = call i8* @__mempcpy_chk(i8* %dst, i8* %src, i64 60, i64 -1)
+  ret i8* %ret
+}
+
+define i8* @test_not_mempcpy() {
+; CHECK-LABEL: @test_not_mempcpy(
+; CHECK-NEXT:    [[RET:%.*]] = call i8* @__mempcpy_chk(i8* getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0), i8* getelementptr inbounds ([60 x i8], [60 x i8]* @b, i64 0, i64 0), i64 60, i64 59)
+; CHECK-NEXT:    ret i8* [[RET]]
+;
+  %dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
+  %src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
+  %ret = call i8* @__mempcpy_chk(i8* %dst, i8* %src, i64 60, i64 59)
+  ret i8* %ret
+}
+
 define i32 @test_snprintf() {
 ; CHECK-LABEL: @test_snprintf(
 ; CHECK-NEXT:    [[SNPRINTF:%.*]] = call i32 (i8*, i64, i8*, ...) @snprintf(i8* nonnull dereferenceable(1) getelementptr inbounds ([60 x i8], [60 x i8]* @a, i64 0, i64 0), i64 60, i8* getelementptr inbounds ([60 x i8], [60 x i8]* @b, i64 0, i64 0))
 ; CHECK-NEXT:    ret i32 [[SNPRINTF]]
 ;
   %dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
   %fmt = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
   %ret = call i32 (i8*, i64, i32, i64, i8*, ...) @__snprintf_chk(i8* %dst, i64 60, i32 0, i64 -1, i8* %fmt)
;
   ; ret i32
   %dst = getelementptr inbounds [60 x i8], [60 x i8]* @a, i32 0, i32 0
   %src = getelementptr inbounds [60 x i8], [60 x i8]* @b, i32 0, i32 0
   %ret = call i32 @__vsprintf_chk(i8* %dst, i32 0, i64 3, i8* %src, %struct.__va_list_tag* null)
   %ign = call i32 @__vsprintf_chk(i8* %dst, i32 1, i64 -1, i8* %src, %struct.__va_list_tag* null)
   ret i32 %ret
 }
 
+declare i8* @__mempcpy_chk(i8*, i8*, i64, i64)
 declare i8* @__memccpy_chk(i8*, i8*, i32, i64, i64)
 declare i32 @__snprintf_chk(i8*, i64, i32, i64, i8*, ...)
 declare i32 @__sprintf_chk(i8*, i32, i64, i8*, ...)
 declare i8* @__strcat_chk(i8*, i8*, i64)
 declare i64 @__strlcat_chk(i8*, i8*, i64, i64)
 declare i8* @__strncat_chk(i8*, i8*, i64, i64)
 declare i64 @__strlcpy_chk(i8*, i8*, i64, i64)
 declare i32 @__vsnprintf_chk(i8*, i64, i32, i64, i8*, %struct.__va_list_tag*)
 declare i32 @__vsprintf_chk(i8*, i32, i64, i8*, %struct.__va_list_tag*)