Extended Description

define i32 @​test(i64 %arg) nounwind {
entry:
%usubo = tail call { i64, i1 } @​llvm.usub.with.overflow.i64(i64 %arg, i64 1)
%overflow = extractvalue { i64, i1 } %usubo, 1
br i1 %overflow, label %merge, label %no_overflow

no_overflow:
br label %merge

merge:
%phi = phi i32 [ 1, %no_overflow ], [ 0, %entry ]
ret i32 %phi
}

declare { i64, i1 } @​llvm.usub.with.overflow.i64(i64, i64)

; RUN: llc -O0 < %s

test: # @​test

%bb.0: # %entry

subq	$1, %rdi setb	%al xorl	%eax, %eax movl	%eax, -4(%rsp) # 4-byte Spill jb	.LBB0_2 

%bb.1: # %no_overflow

movl	$1, %eax movl	%eax, -4(%rsp) # 4-byte Spill jmp	.LBB0_2 

.LBB0_2: # %merge
movl -4(%rsp), %eax # 4-byte Reload
retq

xorl clobbers eflags from subq, used by jb.