[MemCpyOpt] Add test for unreachable capture (NFC)

This is based on the test from D90688, without the argmemonly
attribute. The argmemonly attribute would guaranteed no modref
by itself and the question of captures would not arise in the
first place.

llvm/test/Transforms/MemCpyOpt/callslot.ll

@@ -103,7 +103,7 @@ define void @throw_between_call_and_mempy(i8* dereferenceable(16) %dest.i8) {
 ; CHECK-NEXT:    [[SRC:%.*]] = alloca [16 x i8], align 1
 ; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
 ; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* [[SRC_I8]], i8 0, i64 16, i1 false)
-; CHECK-NEXT:    call void @may_throw() [[ATTR2:#.*]]
+; CHECK-NEXT:    call void @may_throw() #[[ATTR2:[0-9]+]]
 ; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* [[DEST_I8:%.*]], i8 0, i64 16, i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -123,7 +123,7 @@ define void @dest_is_gep_nounwind_call() {
 ; CHECK-NEXT:    [[DEST_I8:%.*]] = getelementptr [16 x i8], [16 x i8]* [[DEST]], i64 0, i64 8
 ; CHECK-NEXT:    [[DEST_I81:%.*]] = bitcast i8* [[DEST_I8]] to [8 x i8]*
 ; CHECK-NEXT:    [[DEST_I812:%.*]] = bitcast [8 x i8]* [[DEST_I81]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I812]]) [[ATTR3:#.*]]
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I812]]) #[[ATTR3:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   %dest = alloca [16 x i8]
@@ -163,7 +163,7 @@ define void @dest_is_gep_requires_movement() {
 ; CHECK-NEXT:    [[DEST_I8:%.*]] = getelementptr [16 x i8], [16 x i8]* [[DEST]], i64 0, i64 8
 ; CHECK-NEXT:    [[DEST_I81:%.*]] = bitcast i8* [[DEST_I8]] to [8 x i8]*
 ; CHECK-NEXT:    [[DEST_I812:%.*]] = bitcast [8 x i8]* [[DEST_I81]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I812]]) [[ATTR3]]
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I812]]) #[[ATTR3]]
 ; CHECK-NEXT:    ret void
 ;
   %dest = alloca [16 x i8]
@@ -183,7 +183,7 @@ define void @capture_before_call_argmemonly() {
 ; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
 ; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I8]])
 ; CHECK-NEXT:    [[DEST1:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) [[ATTR4:#.*]]
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) #[[ATTR4:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   %dest = alloca [16 x i8]
@@ -204,7 +204,7 @@ define void @capture_before_call_argmemonly_nounwind() {
 ; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
 ; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I8]])
 ; CHECK-NEXT:    [[DEST1:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) [[ATTR5:#.*]]
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) #[[ATTR5:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   %dest = alloca [16 x i8]
@@ -226,7 +226,7 @@ define void @capture_before_call_argmemonly_nounwind_willreturn() {
 ; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
 ; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I8]])
 ; CHECK-NEXT:    [[DEST1:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) [[ATTR0:#.*]]
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) #[[ATTR6:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   %dest = alloca [16 x i8]
@@ -239,6 +239,39 @@ define void @capture_before_call_argmemonly_nounwind_willreturn() {
   ret void
 }
 
+; There is no path from the capture back to the memcpy.
+; So we are allowed to perform the call slot optimization.
+define void @capture_nopath_call(i1 %cond) {
+; CHECK-LABEL: @capture_nopath_call(
+; CHECK-NEXT:    [[DEST:%.*]] = alloca [16 x i8], align 1
+; CHECK-NEXT:    [[SRC:%.*]] = alloca [16 x i8], align 1
+; CHECK-NEXT:    [[DEST_I8:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
+; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
+; CHECK-NEXT:    br i1 [[COND:%.*]], label [[CAPTURES:%.*]], label [[NOCAPTURES:%.*]]
+; CHECK:       captures:
+; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I8]])
+; CHECK-NEXT:    ret void
+; CHECK:       nocaptures:
+; CHECK-NEXT:    call void @accept_ptr(i8* [[SRC_I8]]) #[[ATTR3]]
+; CHECK-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i64(i8* [[DEST_I8]], i8* [[SRC_I8]], i64 16, i1 false)
+; CHECK-NEXT:    ret void
+;
+  %dest = alloca [16 x i8]
+  %src = alloca [16 x i8]
+  %dest.i8 = bitcast [16 x i8]* %dest to i8*
+  %src.i8 = bitcast [16 x i8]* %src to i8*
+  br i1 %cond, label %captures, label %nocaptures
+
+captures:
+  call void @accept_ptr(i8* %dest.i8) ; capture
+  ret void
+
+nocaptures:
+  call void @accept_ptr(i8* %src.i8) nounwind
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dest.i8, i8* %src.i8, i64 16, i1 false)
+  ret void
+}
+
 declare void @may_throw()
 declare void @accept_ptr(i8*)
 declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i1)