[Statepoints][ISEL] visitGCRelocate: chain to current DAG root.

This is similar to D87251, but for CopyFromRegs nodes.
Even for local statepoint uses we generate CopyToRegs/CopyFromRegs
nodes.  When generating CopyFromRegs in visitGCRelocate, we must chain
to current DAG root, not EntryNode, to ensure proper ordering of copy
w.r.t. statepoint node producing result for it.

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D88639

Author: dantrushin

llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp

@@ -1123,7 +1123,10 @@ void SelectionDAGBuilder::visitGCRelocate(const GCRelocateInst &Relocate) {
     RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(),
                      DAG.getDataLayout(), InReg, Relocate.getType(),
                      None); // This is not an ABI copy.
-    SDValue Chain = DAG.getEntryNode();
+    // We generate copy to/from regs even for local uses, hence we must
+    // chain with current root to ensure proper ordering of copies w.r.t.
+    // statepoint.
+    SDValue Chain = DAG.getRoot();
     SDValue Relocation = RFV.getCopyFromRegs(DAG, FuncInfo, getCurSDLoc(),
                                              Chain, nullptr, nullptr);
     setValue(&Relocate, Relocation);

llvm/test/CodeGen/X86/statepoint-vreg-details.ll

@@ -18,6 +18,7 @@ declare void @consume5(i32 addrspace(1)*, i32 addrspace(1)*, i32 addrspace(1)*,
 declare void @use1(i32 addrspace(1)*, i8 addrspace(1)*)
 declare i32* @fake_personality_function()
 declare i32 @foo(i32, i8 addrspace(1)*, i32, i32, i32)
+declare void @bar(i8 addrspace(1)*, i8 addrspace(1)*)
 
 ; test most simple relocate
 define i1 @test_relocate(i32 addrspace(1)* %a) gc "statepoint-example" {
@@ -378,6 +379,36 @@ exceptional_return:                         ; preds = %entry
   unreachable
 }
 
+; Test that CopyFromReg emitted during ISEL processing of gc.relocate are properly ordered w.r.t. statepoint.
+define i8 addrspace(1)* @test_isel_sched(i8 addrspace(1)* %0, i8 addrspace(1)* %1, i32 %2) gc "statepoint-example" {
+;CHECK-VREG-LABEL: name:            test_isel_sched
+;CHECK-VREG:  bb.0.entry:
+;CHECK-VREG:        %2:gr32 = COPY $edx
+;CHECK-VREG:        %1:gr64 = COPY $rsi
+;CHECK-VREG:        %0:gr64 = COPY $rdi
+;CHECK-VREG:        TEST32rr %2, %2, implicit-def $eflags
+;CHECK-VREG:        %5:gr64 = CMOV64rr %1, %0, 4, implicit $eflags
+;CHECK-VREG:        MOV64mr %stack.1, 1, $noreg, 0, $noreg, %0 :: (store 8 into %stack.1)
+;CHECK-VREG:        MOV64mr %stack.0, 1, $noreg, 0, $noreg, %1 :: (store 8 into %stack.0)
+;CHECK-VREG:        %6:gr32 = MOV32r0 implicit-def dead $eflags
+;CHECK-VREG:        %7:gr64 = SUBREG_TO_REG 0, killed %6, %subreg.sub_32bit
+;CHECK-VREG:        $rdi = COPY %7
+;CHECK-VREG:        $rsi = COPY %5
+;CHECK-VREG:        %3:gr64, %4:gr64 = STATEPOINT 10, 0, 2, @bar, $rdi, $rsi, 2, 0, 2, 0, 2, 0, 1, 8, %stack.0, 0, %1(tied-def 0), 1, 8, %stack.1, 0, %0(tied-def 1), csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0), (volatile load store 8 on %stack.1)
+;CHECK-VREG:        TEST32rr %2, %2, implicit-def $eflags
+;CHECK-VREG:        %8:gr64 = CMOV64rr %3, %4, 4, implicit $eflags
+;CHECK-VREG:        $rax = COPY %8
+;CHECK-VREG:        RET 0, $rax
+entry:
+  %cmp = icmp eq i32 %2, 0
+  %ptr = select i1 %cmp, i8 addrspace(1)* %0, i8 addrspace(1)* %1
+  %token = call token (i64, i32, void (i8 addrspace(1)*, i8 addrspace(1)*)*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidp1i8p1i8f(i64 10, i32 0, void (i8 addrspace(1)*, i8 addrspace(1)*)* @bar, i32 2, i32 0, i8 addrspace(1)* null, i8 addrspace(1)* %ptr, i32 0, i32 0) [ "deopt"(), "gc-live"(i8 addrspace(1)* %0, i8 addrspace(1)* %1) ]
+  %rel0 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token %token, i32 0, i32 0)
+  %rel1 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token %token, i32 1, i32 1)
+  %res = select i1 %cmp, i8 addrspace(1)* %rel0, i8 addrspace(1)* %rel1
+  ret i8 addrspace(1)* %res
+}
+
 declare token @llvm.experimental.gc.statepoint.p0f_i1f(i64, i32, i1 ()*, i32, i32, ...)
 declare token @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)
 declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token, i32, i32)
@@ -387,4 +418,5 @@ declare i1 @llvm.experimental.gc.result.i1(token)
 declare void @__llvm_deoptimize(i32)
 declare token @llvm.experimental.gc.statepoint.p0f_isVoidi32f(i64 immarg, i32 immarg, void (i32)*, i32 immarg, i32 immarg, ...)
 declare token @llvm.experimental.gc.statepoint.p0f_i32i32p1i8i32i32i32f(i64 immarg, i32 immarg, i32 (i32, i8 addrspace(1)*, i32, i32, i32)*, i32 immarg, i32 immarg, ...)
+declare token @llvm.experimental.gc.statepoint.p0f_isVoidp1i8p1i8f(i64 immarg, i32 immarg, void (i8 addrspace(1)*, i8 addrspace(1)*)*, i32 immarg, i32 immarg, ...)