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[GlobalISel][Legalizer] Look thro copies while combining G_UNMERGE's

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As we're becoming stricter w/ respect to not allowing vregs having LLTs
and regclasses assigned both mid-globalisel pipeline, the number of
extra copies grows, some of which separate G_UNMERGE's from their
corresponding G_MERGE's, becoming a performance concern.

It's worth mentioning that we're already looking through copies while
combining legalization artifacts for every kind of artifact but
G_UNMERGE.

Reviewed By: aditya_nandakumar

Reviewers: ab, t.p.northover, volkan, javed.absar

Subscribers: rovka, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D45644

llvm-svn: 330660
This commit is contained in:
Roman Tereshin 2018-04-23 22:28:36 +00:00
parent 7c338e9b75
commit 68a9fbd154
3 changed files with 43 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/llvm/CodeGen/GlobalISel/LegalizationArtifactCombiner.h
View File

@ -139,9 +139,9 @@ public:
return false;
unsigned NumDefs = MI.getNumOperands() - 1;
unsigned SrcReg = MI.getOperand(NumDefs).getReg();
MachineInstr *MergeI = MRI.getVRegDef(SrcReg);
if (!MergeI || (MergeI->getOpcode() != TargetOpcode::G_MERGE_VALUES))
MachineInstr *MergeI = getOpcodeDef(TargetOpcode::G_MERGE_VALUES,
MI.getOperand(NumDefs).getReg(), MRI);
if (!MergeI)
return false;
const unsigned NumMergeRegs = MergeI->getNumOperands() - 1;
@ -253,11 +253,8 @@ private:
// and as a result, %3, %2, %1 are dead.
MachineInstr *PrevMI = &MI;
while (PrevMI != &DefMI) {
// If we're dealing with G_UNMERGE_VALUES, tryCombineMerges doesn't really try
// to fold copies in between and we can ignore them here.
if (PrevMI->getOpcode() == TargetOpcode::G_UNMERGE_VALUES)
break;
unsigned PrevRegSrc = PrevMI->getOperand(1).getReg();
unsigned PrevRegSrc =
PrevMI->getOperand(PrevMI->getNumOperands() - 1).getReg();
MachineInstr *TmpDef = MRI.getVRegDef(PrevRegSrc);
if (MRI.hasOneUse(PrevRegSrc)) {
if (TmpDef != &DefMI) {
@ -269,9 +266,7 @@ private:
break;
PrevMI = TmpDef;
}
if ((PrevMI == &DefMI ||
DefMI.getOpcode() == TargetOpcode::G_MERGE_VALUES) &&
MRI.hasOneUse(DefMI.getOperand(0).getReg()))
if (PrevMI == &DefMI && MRI.hasOneUse(DefMI.getOperand(0).getReg()))
DeadInsts.push_back(&DefMI);
}

34
test/CodeGen/AArch64/GlobalISel/legalize-combines.mir
View File

@ -8,6 +8,7 @@
define void @test_combines_3() { ret void }
define void @test_combines_4() { ret void }
define void @test_combines_5() { ret void }
define void @test_combines_6() { ret void }
...
---
@ -85,7 +86,38 @@ body: |
%1:_(s32) = G_ADD %0, %0
%2:_(s64) = G_MERGE_VALUES %0, %1
%3:_(s32), %4:_(s32) = G_UNMERGE_VALUES %2
%6:_(s64) = COPY %2
%7:_(s64) = COPY %6
%8:_(s64) = COPY %7
%3:_(s32), %4:_(s32) = G_UNMERGE_VALUES %8
%5:_(s32) = G_ADD %3, %4
$w0 = COPY %5
...
---
name: test_combines_6
body: |
bb.0:
liveins: $w0
; CHECK-LABEL: name: test_combines_6
; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
; CHECK: [[ADD:%[0-9]+]]:_(s32) = G_ADD [[COPY]], [[COPY]]
; CHECK: [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[COPY]](s32), [[ADD]](s32)
; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY [[MV]](s64)
; CHECK: [[COPY2:%[0-9]+]]:_(s64) = COPY [[COPY1]](s64)
; CHECK: [[ADD1:%[0-9]+]]:_(s32) = G_ADD [[COPY]], [[ADD]]
; CHECK: $w0 = COPY [[ADD1]](s32)
; CHECK: $x0 = COPY [[COPY2]](s64)
%0:_(s32) = COPY $w0
%1:_(s32) = G_ADD %0, %0
%2:_(s64) = G_MERGE_VALUES %0, %1
%6:_(s64) = COPY %2
%7:_(s64) = COPY %6
%8:_(s64) = COPY %7
%3:_(s32), %4:_(s32) = G_UNMERGE_VALUES %8
%5:_(s32) = G_ADD %3, %4
$w0 = COPY %5
$x0 = COPY %7
...

9
test/CodeGen/AArch64/GlobalISel/legalize-nonpowerof2eltsvec.mir
View File

@ -23,12 +23,11 @@ body: |
; CHECK-LABEL: name: test_legalize_merge_v3s64
; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
; CHECK: [[MV:%[0-9]+]]:_(<3 x s64>) = G_MERGE_VALUES [[COPY]](s64), [[COPY]](s64), [[COPY]](s64)
; CHECK: [[COPY1:%[0-9]+]]:_(<3 x s64>) = COPY [[MV]](<3 x s64>)
; CHECK: [[UV:%[0-9]+]]:_(s64), [[UV1:%[0-9]+]]:_(s64), [[UV2:%[0-9]+]]:_(s64) = G_UNMERGE_VALUES [[COPY1]](<3 x s64>)
; CHECK: $x0 = COPY [[UV]](s64)
; CHECK: $x0 = COPY [[COPY]](s64)
; CHECK: $noreg = PATCHABLE_RET [[MV]](<3 x s64>)
%0(s64) = COPY $x0
%1(<3 x s64>) = G_MERGE_VALUES %0(s64), %0(s64), %0(s64)
%2(<3 x s64>) = COPY %1(<3 x s64>)
%3(s64), %4(s64), %5(s64) = G_UNMERGE_VALUES %2(<3 x s64>)
%2(s64), %3(s64), %4(s64) = G_UNMERGE_VALUES %1(<3 x s64>)
$x0 = COPY %3(s64)
$noreg = PATCHABLE_RET %1(<3 x s64>)
...