[MemLoc] Support memcmp in MemoryLocation::getForArgument.

This patch adds support for memcmp in MemoryLocation::getForArgument.
memcmp reads from the first 2 arguments up to the number of bytes of the
third argument.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D86725

Author: fhahn

llvm/lib/Analysis/MemoryLocation.cpp

@@ -210,17 +210,29 @@ MemoryLocation MemoryLocation::getForArgument(const CallBase *Call,
   // LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
   // whenever possible.
   LibFunc F;
-  if (TLI && Call->getCalledFunction() &&
-      TLI->getLibFunc(*Call->getCalledFunction(), F) &&
-      F == LibFunc_memset_pattern16 && TLI->has(F)) {
-    assert((ArgIdx == 0 || ArgIdx == 1) &&
-           "Invalid argument index for memset_pattern16");
-    if (ArgIdx == 1)
-      return MemoryLocation(Arg, LocationSize::precise(16), AATags);
-    if (const ConstantInt *LenCI =
-            dyn_cast<ConstantInt>(Call->getArgOperand(2)))
-      return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
-                            AATags);
+  if (TLI && TLI->getLibFunc(*Call, F) && TLI->has(F)) {
+    switch (F) {
+    case LibFunc_memset_pattern16:
+      assert((ArgIdx == 0 || ArgIdx == 1) &&
+             "Invalid argument index for memset_pattern16");
+      if (ArgIdx == 1)
+        return MemoryLocation(Arg, LocationSize::precise(16), AATags);
+      if (const ConstantInt *LenCI =
+              dyn_cast<ConstantInt>(Call->getArgOperand(2)))
+        return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
+                              AATags);
+      break;
+    case LibFunc_memcmp:
+      assert((ArgIdx == 0 || ArgIdx == 1) &&
+             "Invalid argument index for memcmp");
+      if (const ConstantInt *LenCI =
+              dyn_cast<ConstantInt>(Call->getArgOperand(2)))
+        return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
+                              AATags);
+      break;
+    default:
+      break;
+    };
   }
   // FIXME: Handle memset_pattern4 and memset_pattern8 also.
 

llvm/test/Analysis/BasicAA/libfuncs.ll

@@ -7,9 +7,9 @@ target triple = "x86_64-apple-macosx10.7"
 ; CHECK:      Just Ref:  Ptr: i8* %a	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
 ; CHECK-NEXT: Just Ref:  Ptr: i8* %b	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
 ; CHECK-NEXT: Just Ref:  Ptr: i8* %a.gep.1	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
-; CHECK-NEXT: Just Ref:  Ptr: i8* %a.gep.5	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
+; CHECK-NEXT: NoModRef:  Ptr: i8* %a.gep.5	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
 ; CHECK-NEXT: Just Ref:  Ptr: i8* %b.gep.1	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
-; CHECK-NEXT: Just Ref:  Ptr: i8* %b.gep.5	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
+; CHECK-NEXT: NoModRef:  Ptr: i8* %b.gep.5	<->  %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)
 define i32 @test_memcmp_const_size(i8* noalias %a, i8* noalias %b) {
 entry:
   %res = tail call i32 @memcmp(i8* %a, i8* %b, i64 4)

llvm/test/Transforms/DeadStoreElimination/MSSA/libcalls.ll

@@ -85,10 +85,6 @@ define i32 @test_memcmp_const_size(i8* noalias %foo) {
 ; CHECK-NEXT:    store i8 49, i8* [[STACK_PTR]], align 1
 ; CHECK-NEXT:    [[GEP_1:%.*]] = getelementptr i8, i8* [[STACK_PTR]], i64 1
 ; CHECK-NEXT:    store i8 50, i8* [[GEP_1]], align 1
-; CHECK-NEXT:    [[GEP_2:%.*]] = getelementptr i8, i8* [[STACK_PTR]], i64 2
-; CHECK-NEXT:    store i8 51, i8* [[GEP_2]], align 1
-; CHECK-NEXT:    [[GEP_3:%.*]] = getelementptr i8, i8* [[STACK_PTR]], i64 3
-; CHECK-NEXT:    store i8 52, i8* [[GEP_3]], align 1
 ; CHECK-NEXT:    [[RES:%.*]] = call i32 @memcmp(i8* nonnull dereferenceable(2) [[FOO:%.*]], i8* nonnull dereferenceable(2) [[STACK_PTR]], i64 2)
 ; CHECK-NEXT:    ret i32 [[RES]]
 ;