%c = icmp eq i32* %x, null
; It isn't legal to move the load from %x from "not_null" to here --
; the store to %y could be aliasing it.
- br i1 %c, label %is_null, label %not_null
+ br i1 %c, label %is_null, label %not_null, !make.implicit !0
is_null:
ret i32 42
define i32 @imp_null_check_gep_load(i32* %x) {
entry:
%c = icmp eq i32* %x, null
- br i1 %c, label %is_null, label %not_null
+ br i1 %c, label %is_null, label %not_null, !make.implicit !0
is_null:
ret i32 42
%t = load i32, i32* %x.gep
ret i32 %t
}
+
+define i32 @imp_null_check_load_no_md(i32* %x) {
+; This is fine, except it is missing the !make.implicit metadata.
+ entry:
+ %c = icmp eq i32* %x, null
+ br i1 %c, label %is_null, label %not_null
+
+ is_null:
+ ret i32 42
+
+ not_null:
+ %t = load i32, i32* %x
+ ret i32 %t
+}
+
+define i32 @imp_null_check_no_hoist_over_acquire_load(i32* %x, i32* %y) {
+; We cannot hoist %t1 over %t0 since %t0 is an acquire load
+ entry:
+ %c = icmp eq i32* %x, null
+ br i1 %c, label %is_null, label %not_null, !make.implicit !0
+
+ is_null:
+ ret i32 42
+
+ not_null:
+ %t0 = load atomic i32, i32* %y acquire, align 4
+ %t1 = load i32, i32* %x
+ %p = add i32 %t0, %t1
+ ret i32 %p
+}
+
+define i32 @imp_null_check_add_result(i32* %x, i32* %y) {
+; This will codegen to:
+;
+; movl (%rsi), %eax
+; addl (%rdi), %eax
+;
+; The load instruction we wish to hoist is the addl, but there is a
+; write-after-write hazard preventing that from happening. We could
+; get fancy here and exploit the commutativity of addition, but right
+; now -implicit-null-checks isn't that smart.
+;
+
+ entry:
+ %c = icmp eq i32* %x, null
+ br i1 %c, label %is_null, label %not_null, !make.implicit !0
+
+ is_null:
+ ret i32 42
+
+ not_null:
+ %t0 = load i32, i32* %y
+ %t1 = load i32, i32* %x
+ %p = add i32 %t0, %t1
+ ret i32 %p
+}
+
+!0 = !{}