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This test case:

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long test(long x) { return (x & 123124) | 3; }

Currently compiles to:

_test:
        orl     $3, %edi
        movq    %rdi, %rax
        andq    $123127, %rax
        ret

This is because instruction and DAG combiners canonicalize

  (or (and x, C), D) -> (and (or, D), (C | D))

However, this is only profitable if (C & D) != 0. It gets in the way of the
3-addressification because the input bits are known to be zero.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97616 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling
2010-03-03 00:35:56 +00:00
parent a43398283d
commit 7d9f2b93a3
4 changed files with 35 additions and 19 deletions
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28
test/CodeGen/X86/and-or-fold.ll
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@@ -1,14 +1,26 @@
; RUN: llc < %s -march=x86 | grep and | count 1
; RUN: llc < %s -mtriple=i686-apple-darwin | FileCheck -check-prefix=DARWIN %s
; RUN: opt < %s -O2 | llc -mtriple=x86_64-apple-darwin | FileCheck -check-prefix=DARWIN-OPT %s
; The dag combiner should fold together (x&127)|(y&16711680) -> (x|y)&c1
; in this case.
define i32 @test6(i32 %x, i16 %y) {
%tmp1 = zext i16 %y to i32 ; <i32> [#uses=1]
%tmp2 = and i32 %tmp1, 127 ; <i32> [#uses=1]
%tmp4 = shl i32 %x, 16 ; <i32> [#uses=1]
%tmp5 = and i32 %tmp4, 16711680 ; <i32> [#uses=1]
%tmp6 = or i32 %tmp2, %tmp5 ; <i32> [#uses=1]
ret i32 %tmp6
define i32 @test1(i32 %x, i16 %y) {
%tmp1 = zext i16 %y to i32
%tmp2 = and i32 %tmp1, 127
%tmp4 = shl i32 %x, 16
%tmp5 = and i32 %tmp4, 16711680
%tmp6 = or i32 %tmp2, %tmp5
ret i32 %tmp6
; DARWIN: andl $16711807, %eax
}
; <rdar://problem/7529774> The optimizer shouldn't fold this into (and (or, C), D)
; if (C & D) == 0
define i64 @test2(i64 %x) nounwind readnone ssp {
entry:
%tmp1 = and i64 %x, 123127
%tmp2 = or i64 %tmp1, 3
ret i64 %tmp2
; DARWIN-OPT: andq $123124
; DARWIN-OPT-NEXT: leaq 3
}