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[X86] Add BSR to isUseDefConvertible. 

We already had BSF here as part of __builtin_ffs improvements and I was just wondering yesterday whether we should have BSR there.

This addresses one issue from PR40090.

llvm-svn: 349531
This commit is contained in:
Craig Topper 2018-12-18 20:03:54 +00:00
parent 20853a7807
commit 18a9d545e1
2 changed files with 30 additions and 6 deletions
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12
llvm/lib/Target/X86/X86InstrInfo.cpp
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@ -3579,12 +3579,12 @@ static X86::CondCode isUseDefConvertible(const MachineInstr &MI) {
case X86::TZCNT32rr: case X86::TZCNT32rm:
case X86::TZCNT64rr: case X86::TZCNT64rm:
return X86::COND_B;
case X86::BSF16rr:
case X86::BSF16rm:
case X86::BSF32rr:
case X86::BSF32rm:
case X86::BSF64rr:
case X86::BSF64rm:
case X86::BSF16rr: case X86::BSF16rm:
case X86::BSF32rr: case X86::BSF32rm:
case X86::BSF64rr: case X86::BSF64rm:
case X86::BSR16rr: case X86::BSR16rm:
case X86::BSR32rr: case X86::BSR32rm:
case X86::BSR64rr: case X86::BSR64rm:
return X86::COND_E;
}
}

24
llvm/test/CodeGen/X86/pr40090.ll Normal file
View File

@ -0,0 +1,24 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
define i64 @foo(i64 %x, i64 %y) {
; CHECK-LABEL: foo:
; CHECK: # %bb.0:
; CHECK-NEXT: bsrq %rdi, %rax
; CHECK-NEXT: xorq $64, %rax
; CHECK-NEXT: bsrq %rsi, %rcx
; CHECK-NEXT: cmoveq %rax, %rcx
; CHECK-NEXT: movl $63, %eax
; CHECK-NEXT: subq %rcx, %rax
; CHECK-NEXT: retq
%1 = tail call i64 @llvm.ctlz.i64(i64 %x, i1 true)
%2 = xor i64 %1, 127
%3 = tail call i64 @llvm.ctlz.i64(i64 %y, i1 true)
%4 = xor i64 %3, 63
%5 = icmp eq i64 %y, 0
%6 = select i1 %5, i64 %2, i64 %4
%7 = sub nsw i64 63, %6
ret i64 %7
}
declare i64 @llvm.ctlz.i64(i64, i1)