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https://github.com/c64scene-ar/llvm-6502.git
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f2d7693fbb
use the zero-undefined variants of CTTZ and CTLZ. These are just simple patterns for now, there is more to be done to make real world code using these constructs be optimized and codegen'ed properly on X86. The existing tests are spiffed up to check that we no longer generate unnecessary cmov instructions, and that we generate the very important 'xor' to transform bsr which counts the index of the most significant one bit to the number of leading (most significant) zero bits. Also they now check that when the variant with defined zero result is used, the cmov is still produced. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146974 91177308-0d34-0410-b5e6-96231b3b80d8
66 lines
1.4 KiB
LLVM
66 lines
1.4 KiB
LLVM
; RUN: llc < %s -march=x86 -mcpu=yonah | FileCheck %s
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define i32 @t1(i32 %x) nounwind {
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%tmp = tail call i32 @llvm.ctlz.i32( i32 %x, i1 true )
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ret i32 %tmp
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; CHECK: t1:
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; CHECK: bsrl
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; CHECK-NOT: cmov
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; CHECK: xorl $31,
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; CHECK: ret
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}
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declare i32 @llvm.ctlz.i32(i32, i1) nounwind readnone
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define i32 @t2(i32 %x) nounwind {
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%tmp = tail call i32 @llvm.cttz.i32( i32 %x, i1 true )
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ret i32 %tmp
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; CHECK: t2:
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; CHECK: bsfl
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; CHECK-NOT: cmov
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; CHECK: ret
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}
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declare i32 @llvm.cttz.i32(i32, i1) nounwind readnone
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define i16 @t3(i16 %x, i16 %y) nounwind {
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entry:
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%tmp1 = add i16 %x, %y
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%tmp2 = tail call i16 @llvm.ctlz.i16( i16 %tmp1, i1 true ) ; <i16> [#uses=1]
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ret i16 %tmp2
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; CHECK: t3:
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; CHECK: bsrw
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; CHECK-NOT: cmov
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; CHECK: xorw $15,
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; CHECK: ret
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}
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declare i16 @llvm.ctlz.i16(i16, i1) nounwind readnone
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define i32 @t4(i32 %n) nounwind {
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entry:
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; Generate a cmov to handle zero inputs when necessary.
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; CHECK: t4:
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; CHECK: bsrl
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; CHECK: cmov
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; CHECK: xorl $31,
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; CHECK: ret
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%tmp1 = tail call i32 @llvm.ctlz.i32(i32 %n, i1 false)
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ret i32 %tmp1
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}
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define i32 @t5(i32 %n) nounwind {
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entry:
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; Don't generate the cmovne when the source is known non-zero (and bsr would
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; not set ZF).
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; rdar://9490949
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; CHECK: t5:
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; CHECK: bsrl
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; CHECK-NOT: cmov
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; CHECK: xorl $31,
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; CHECK: ret
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%or = or i32 %n, 1
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%tmp1 = tail call i32 @llvm.ctlz.i32(i32 %or, i1 false)
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ret i32 %tmp1
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}
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