[LIR] Set attributes on memset_pattern16.

[ab]

Summary

"inferattrs" will deduce the attribute, but it will be too late for many optimizations.

[mcrosier]

@haicheng, would you mind giving this a look? If not, I can look at this tomorrow.

[haicheng]

I have no problem with this change.

[ab]

This is IMO a little too hacky; what do you think of exposing inferattrs into a utility function?

[mcrosier]

In D17598#362168, @ab wrote:

This is IMO a little too hacky;

I tend to agree with Ahmed..

[ab]

Now that we have a unified way of setting attributes, use it.

Depends on D19470 and D19471.

[mehdi_amini]

Thanks Ahmed. LGTM.

llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BuildLibCalls.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "loop-idiom"
 
 STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
 STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
bool LoopIdiomRecognize::processLoopStridedStore(
   } else {
     // Everything is emitted in default address space
     Type *Int8PtrTy = DestInt8PtrTy;
 
     Module *M = TheStore->getModule();
     Value *MSP =
         M->getOrInsertFunction("memset_pattern16", Builder.getVoidTy(),
                                Int8PtrTy, Int8PtrTy, IntPtr, (void *)nullptr);
+    inferLibFuncAttributes(*M->getFunction("memset_pattern16"), *TLI);
 
     // Otherwise we should form a memset_pattern16.  PatternValue is known to be
     // an constant array of 16-bytes.  Plop the value into a mergable global.
     GlobalVariable *GV = new GlobalVariable(*M, PatternValue->getType(), true,
                                             GlobalValue::PrivateLinkage,
                                             PatternValue, ".memset_pattern");
     GV->setUnnamedAddr(true); // Ok to merge these.
     GV->setAlignment(16);

llvm/trunk/test/Transforms/LoopIdiom/basic.ll

 
 for.end6:                                         ; preds = %for.inc4
   ret void
 ; CHECK-LABEL: @test19(
 ; CHECK: entry:
 ; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %X, i8 0, i64 10000, i32 1, i1 false)
 ; CHECK: ret void
 }
+
+; Validate that "memset_pattern" has the proper attributes.
+; CHECK: declare void @memset_pattern16(i8* nocapture, i8* nocapture readonly, i64) [[ATTRS:#[0-9]+]]
+; CHECK: [[ATTRS]] = { argmemonly }