maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/test/CodeGen/X86/2014-05-29-factorial.ll

25 lines
661 B
LLVM
Raw Normal View History

[X86] Avoid emitting unnecessary test instructions. This patch teaches the backend how to check for the 'NoSignedWrap' flag on binary operations to improve the emission of 'test' instructions. If the result of a binary operation is known not to overflow we know that resetting the Overflow flag is unnecessary and so we can avoid emitting the test instruction. Patch by Marcello Maggioni. llvm-svn: 210468
2014-06-09 20:34:50 +08:00
; RUN: llc < %s -march=x86-64 | FileCheck %s
llvm/test/CodeGen/X86/2014-05-29-factorial.ll: Relax an expression to match Win32 x64. llvm-svn: 210471
2014-06-09 22:20:23 +08:00
; CHECK: decq [[X:%rdi|%rcx]]
; CHECK-NOT: testq [[X]], [[X]]
[X86] Avoid emitting unnecessary test instructions. This patch teaches the backend how to check for the 'NoSignedWrap' flag on binary operations to improve the emission of 'test' instructions. If the result of a binary operation is known not to overflow we know that resetting the Overflow flag is unnecessary and so we can avoid emitting the test instruction. Patch by Marcello Maggioni. llvm-svn: 210468
2014-06-09 20:34:50 +08:00
define i64 @fact2(i64 %x) {
entry:
br label %while.body
while.body:
%result.06 = phi i64 [ %mul, %while.body ], [ 1, %entry ]
%x.addr.05 = phi i64 [ %dec, %while.body ], [ %x, %entry ]
%mul = mul nsw i64 %result.06, %x.addr.05
%dec = add nsw i64 %x.addr.05, -1
%cmp = icmp sgt i64 %dec, 0
br i1 %cmp, label %while.body, label %while.end.loopexit
while.end.loopexit:
%mul.lcssa = phi i64 [ %mul, %while.body ]
br label %while.end
while.end:
%result.0.lcssa = phi i64 [ %mul.lcssa, %while.end.loopexit ]
ret i64 %result.0.lcssa
}