[PATCH] D76013: [GC] Loosen ordering on statepoint reloads to allow CSE
Philip Reames via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 11 12:30:27 PDT 2020
This revision was automatically updated to reflect the committed changes.
Closed by commit rG8f997b4f0118: [GC] Loosen ordering on statepoint reloads to allow CSE (authored by reames).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D76013/new/
https://reviews.llvm.org/D76013
Files:
llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
llvm/test/CodeGen/X86/statepoint-duplicates-export.ll
Index: llvm/test/CodeGen/X86/statepoint-duplicates-export.ll
===================================================================
--- llvm/test/CodeGen/X86/statepoint-duplicates-export.ll
+++ llvm/test/CodeGen/X86/statepoint-duplicates-export.ll
@@ -44,19 +44,16 @@
define i1 @test2(i32 addrspace(1)* %arg) gc "statepoint-example" {
; CHECK-LABEL: test2:
; CHECK: # %bb.0: # %entry
-; CHECK-NEXT: subq $24, %rsp
-; CHECK-NEXT: .cfi_def_cfa_offset 32
-; CHECK-NEXT: movq %rdi, {{[0-9]+}}(%rsp)
+; CHECK-NEXT: pushq %rax
+; CHECK-NEXT: .cfi_def_cfa_offset 16
+; CHECK-NEXT: movq %rdi, (%rsp)
; CHECK-NEXT: callq func
; CHECK-NEXT: .Ltmp2:
-; CHECK-NEXT: movq {{[0-9]+}}(%rsp), %rax
-; CHECK-NEXT: movq %rax, {{[0-9]+}}(%rsp)
; CHECK-NEXT: callq func
; CHECK-NEXT: .Ltmp3:
-; CHECK-NEXT: movq {{[0-9]+}}(%rsp), %rax
-; CHECK-NEXT: orq {{[0-9]+}}(%rsp), %rax
+; CHECK-NEXT: cmpq $0, (%rsp)
; CHECK-NEXT: sete %al
-; CHECK-NEXT: addq $24, %rsp
+; CHECK-NEXT: popq %rcx
; CHECK-NEXT: .cfi_def_cfa_offset 8
; CHECK-NEXT: retq
entry:
Index: llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
+++ llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
@@ -973,10 +973,13 @@
unsigned Index = *DerivedPtrLocation;
SDValue SpillSlot = DAG.getTargetFrameIndex(Index, getFrameIndexTy());
- // Note: We know all of these reloads are independent, but don't bother to
- // exploit that chain wise. DAGCombine will happily do so as needed, so
- // doing it here would be a small compile time win at most.
- SDValue Chain = getRoot();
+ // All the reloads are independent and are reading memory only modified by
+ // statepoints (i.e. no other aliasing stores); informing SelectionDAG of
+ // this this let's CSE kick in for free and allows reordering of instructions
+ // if possible. The lowering for statepoint sets the root, so this is
+ // ordering all reloads with the either a) the statepoint node itself, or b)
+ // the entry of the current block for an invoke statepoint.
+ const SDValue Chain = DAG.getRoot(); // != Builder.getRoot()
auto &MF = DAG.getMachineFunction();
auto &MFI = MF.getFrameInfo();
@@ -991,8 +994,7 @@
SDValue SpillLoad = DAG.getLoad(LoadVT, getCurSDLoc(), Chain,
SpillSlot, LoadMMO);
-
- DAG.setRoot(SpillLoad.getValue(1));
+ PendingLoads.push_back(SpillLoad.getValue(1));
assert(SpillLoad.getNode());
setValue(&Relocate, SpillLoad);
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