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RBIT Instruction only available for ARMv6t2 and above. 

Summary:
r255334 matches bit-reverse pattern in InstCombine and generates calls to Instrinsic::bitreverse.

RBIT instruction is only available for ARMv6t2 and above. This patch has the intrinsic expanded during legalization for ARMv4 and ARMv5.

Patch by Z. Zheng <zhaoshiz@codeaurora.org>

Reviewers: apazos, jmolloy, weimingz

Subscribers: aemerson, rengolin, llvm-commits

Differential Revision: http://reviews.llvm.org/D15932

llvm-svn: 257188
This commit is contained in:
Weiming Zhao 2016-01-08 18:43:41 +00:00
parent 48c033e021
commit 4b3b13d3bc
2 changed files with 35 additions and 1 deletions
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2
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -744,7 +744,7 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
setOperationAction(ISD::SUBE, MVT::i32, Custom);
}
if (!Subtarget->isThumb1Only())
if (!Subtarget->isThumb1Only() && Subtarget->hasV6T2Ops())
setOperationAction(ISD::BITREVERSE, MVT::i32, Legal);
// ARM does not have ROTL.

34
llvm/test/CodeGen/ARM/bit-reverse-to-rbit.ll Normal file
View File

@ -0,0 +1,34 @@
;RUN: opt -instcombine -S < %s | llc -mtriple=armv5e--linux-gnueabi | FileCheck %s
;RUN: opt -instcombine -S < %s | llc -mtriple=thumbv4t--linux-gnueabi | FileCheck %s
;RUN: opt -instcombine -S < %s | llc -mtriple=armv6--linux-gnueabi | FileCheck %s
;RUN: opt -instcombine -S < %s | llc -mtriple=armv7--linux-gnueabi | FileCheck %s --check-prefix=RBIT
;RUN: opt -instcombine -S < %s | llc -mtriple=thumbv8--linux-gnueabi | FileCheck %s --check-prefix=RBIT
;CHECK-NOT: rbit
;RBIT: rbit
define void @byte_reversal(i8* %p, i32 %n) {
entry:
br label %for.cond
for.cond: ; preds = %for.body, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
%cmp = icmp ult i32 %i.0, %n
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%0 = sext i32 %i.0 to i64
%arrayidx = getelementptr inbounds i8, i8* %p, i64 %0
%1 = load i8, i8* %arrayidx, align 1
%or19 = call i8 @llvm.bitreverse.i8(i8 %1)
store i8 %or19, i8* %arrayidx, align 1
%inc = add i32 %i.0, 1
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
; Function Attrs: nounwind readnone
declare i8 @llvm.bitreverse.i8(i8)