llvm/test/CodeGen/X86/ctpop-combine.ll
Jim Grosbach e1af5f6ad1 X86: Perform integer comparisons at i32 or larger.
Utilizing the 8 and 16 bit comparison instructions, even when an input can
be folded into the comparison instruction itself, is typically not worth it.
There are too many partial register stalls as a result, leading to significant
slowdowns. By always performing comparisons on at least 32-bit
registers, performance of the calculation chain leading to the
comparison improves. Continue to use the smaller comparisons when
minimizing size, as that allows better folding of loads into the
comparison instructions.

rdar://15386341

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195496 91177308-0d34-0410-b5e6-96231b3b80d8
2013-11-22 19:57:47 +00:00

41 lines
985 B
LLVM

; RUN: llc -march=x86-64 -mcpu=corei7 < %s | FileCheck %s
declare i64 @llvm.ctpop.i64(i64) nounwind readnone
define i32 @test1(i64 %x) nounwind readnone {
%count = tail call i64 @llvm.ctpop.i64(i64 %x)
%cast = trunc i64 %count to i32
%cmp = icmp ugt i32 %cast, 1
%conv = zext i1 %cmp to i32
ret i32 %conv
; CHECK-LABEL: test1:
; CHECK: leaq -1([[A0:%rdi|%rcx]])
; CHECK-NEXT: testq
; CHECK-NEXT: setne
; CHECK: ret
}
define i32 @test2(i64 %x) nounwind readnone {
%count = tail call i64 @llvm.ctpop.i64(i64 %x)
%cmp = icmp ult i64 %count, 2
%conv = zext i1 %cmp to i32
ret i32 %conv
; CHECK-LABEL: test2:
; CHECK: leaq -1([[A0]])
; CHECK-NEXT: testq
; CHECK-NEXT: sete
; CHECK: ret
}
define i32 @test3(i64 %x) nounwind readnone {
%count = tail call i64 @llvm.ctpop.i64(i64 %x)
%cast = trunc i64 %count to i6 ; Too small for 0-64
%cmp = icmp ult i6 %cast, 2
%conv = zext i1 %cmp to i32
ret i32 %conv
; CHECK-LABEL: test3:
; CHECK: cmpl $2
; CHECK: ret
}