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[ARM][LowOverheadLoops] Remove modifications to the correct element 

count register

After my patch at D86087, code that now uses the mov operand rather than
the vctp operand will no longer remove modifications to the vctp operand
as they should. This patch fixes that by explicitly removing
modifications to the vctp operand rather than the register used as the
element count.
This commit is contained in:
Sam Tebbs 2020-09-07 10:39:14 +01:00
parent 8d9c13f37d
commit 7aabb6ad77
3 changed files with 8 additions and 5 deletions
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7
llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
View File

@ -527,7 +527,12 @@ bool LowOverheadLoop::ValidateTailPredicate(MachineInstr *StartInsertPt) {
};
MBB = VCTP->getParent();
if (auto *Def = RDA.getUniqueReachingMIDef(&MBB->back(), NumElements)) {
// Remove modifications to the element count since they have no purpose in a
// tail predicated loop. Explicitly refer to the vctp operand no matter which
// register NumElements has been assigned to, since that is what the
// modifications will be using
if (auto *Def = RDA.getUniqueReachingMIDef(&MBB->back(),
VCTP->getOperand(1).getReg())) {
SmallPtrSet<MachineInstr*, 2> ElementChain;
SmallPtrSet<MachineInstr*, 2> Ignore = { VCTP };
unsigned ExpectedVectorWidth = getTailPredVectorWidth(VCTP->getOpcode());

5
llvm/test/CodeGen/Thumb2/LowOverheadLoops/mov-after-dlstp.mir
View File

@ -173,11 +173,10 @@ body: |
; CHECK: renamable $r3 = VMOVRS killed renamable $s0, 14 /* CC::al */, $noreg
; CHECK: renamable $q0 = MVE_VMOVimmi32 0, 0, $noreg, undef renamable $q0
; CHECK: renamable $q1 = MVE_VDUP32 killed renamable $r3, 0, $noreg, undef renamable $q1
; CHECK: $r3 = tMOVr $r1, 14 /* CC::al */, $noreg
; CHECK: dead $r3 = tMOVr $r1, 14 /* CC::al */, $noreg
; CHECK: bb.3.do.body:
; CHECK: successors: %bb.3(0x7c000000), %bb.4(0x04000000)
; CHECK: liveins: $lr, $q0, $q1, $r0, $r1, $r2, $r3
; CHECK: renamable $r3, dead $cpsr = tSUBi8 killed renamable $r3, 4, 14 /* CC::al */, $noreg
; CHECK: liveins: $lr, $q0, $q1, $r0, $r1, $r2
; CHECK: renamable $r0, renamable $q2 = MVE_VLDRWU32_post killed renamable $r0, 16, 0, $noreg :: (load 16 from %ir.pSrc.addr.01, align 4)
; CHECK: renamable $q2 = nnan ninf nsz arcp contract afn reassoc MVE_VSUBf32 killed renamable $q2, renamable $q1, 0, $noreg, undef renamable $q2
; CHECK: renamable $q0 = nnan ninf nsz arcp contract afn reassoc MVE_VFMAf32 killed renamable $q0, killed renamable $q2, killed renamable $q2, 0, killed $noreg

1
llvm/test/CodeGen/Thumb2/LowOverheadLoops/mov-operand.ll
View File

@ -27,7 +27,6 @@ define arm_aapcs_vfpcc void @arm_var_f32_mve(float* %pSrc, i32 %blockSize, float
; CHECK-NEXT: mov r3, r1
; CHECK-NEXT: .LBB0_3: @ %do.body
; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
; CHECK-NEXT: subs r3, #4
; CHECK-NEXT: vldrw.u32 q2, [r0], #16
; CHECK-NEXT: vsub.f32 q2, q2, q1
; CHECK-NEXT: vfma.f32 q0, q2, q2