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[PowerPC] Don't combine to bswap store on 1-byte truncating store 

Turns out that there was no check for a store that truncates down
to a single byte when combining a (store (bswap...)) into a byte-swapping
store. This patch just adds that check.

Fixes https://bugs.llvm.org/show_bug.cgi?id=39478.

llvm-svn: 347288
This commit is contained in:
Nemanja Ivanovic 2018-11-20 04:42:31 +00:00
parent 4954c66430
commit 9b393909e2
2 changed files with 29 additions and 2 deletions
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5
llvm/lib/Target/PowerPC/PPCISelLowering.cpp
View File

@ -12604,9 +12604,10 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
(Op1VT == MVT::i32 || Op1VT == MVT::i16 ||
(Subtarget.hasLDBRX() && Subtarget.isPPC64() && Op1VT == MVT::i64))) {
// STBRX can only handle simple types.
// STBRX can only handle simple types and it makes no sense to store less
// two bytes in byte-reversed order.
EVT mVT = cast<StoreSDNode>(N)->getMemoryVT();
if (mVT.isExtended())
if (mVT.isExtended() || mVT.getSizeInBits() < 16)
break;
SDValue BSwapOp = N->getOperand(1).getOperand(0);

26
llvm/test/CodeGen/PowerPC/pr39478.ll Normal file
View File

@ -0,0 +1,26 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=powerpc64le-unknown-unknown -verify-machineinstrs < %s | \
; RUN: FileCheck %s
; RUN: llc -mtriple=powerpc64-unknown-unknown -verify-machineinstrs < %s | \
; RUN: FileCheck %s
define void @pr39478() {
; CHECK-LABEL: pr39478:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: lwz 3, 0(3)
; CHECK-NEXT: stb 3, 0(3)
; CHECK-NEXT: blr
entry:
%tmp32 = load i64, i64* undef, align 8
%tmp33 = load i32, i32* undef, align 4
%tmp34 = and i32 %tmp33, -256
%tmp35 = lshr i64 %tmp32, 32
%tmp36 = shl nuw nsw i64 %tmp35, 24
%tmp37 = trunc i64 %tmp36 to i32
%tmp38 = call i32 @llvm.bswap.i32(i32 %tmp37)
%tmp39 = or i32 %tmp38, %tmp34
store i32 %tmp39, i32* undef, align 4
ret void
}
declare i32 @llvm.bswap.i32(i32)