llvm/test/CodeGen/X86/saddo-redundant-add.ll
Juergen Ributzka fe08a38a2c [X86] Prevent the creation of redundant ops for sadd and ssub with overflow.
This commit teaches the X86 backend to create the same X86 instructions when it
lowers an sadd/ssub with overflow intrinsic and a conditional branch that uses
that overflow result. This allows SelectionDAG to recognize and remove one of
the redundant operations.

This fixes <rdar://problem/15874016> and <rdar://problem/15661073>.

Reviewed by Nadav

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199976 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 06:47:57 +00:00

35 lines
805 B
LLVM

; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
define void @redundant_add(i64 %n) {
; Check that we don't create two additions for the sadd.with.overflow.
; CHECK-LABEL: redundant_add
; CHECK-NOT: leaq
; CHECK-NOT: addq
; CHECK: incq
; CHECK-NEXT: jno
entry:
br label %exit_check
exit_check:
%i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
%c = icmp slt i64 %i, %n
br i1 %c, label %loop, label %exit
loop:
%i.o = tail call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %i, i64 1)
%i.next = extractvalue { i64, i1 } %i.o, 0
%o = extractvalue { i64, i1 } %i.o, 1
br i1 %o, label %overflow, label %exit_check
exit:
ret void
overflow:
tail call void @llvm.trap()
unreachable
}
declare { i64, i1 } @llvm.sadd.with.overflow.i64(i64, i64)
declare void @llvm.trap()