From: Philip Reames Date: Fri, 5 Mar 2021 17:55:36 +0000 (-0800) Subject: [rs4gc] avoid insert base computation instructions for deopt uses X-Git-Tag: llvmorg-14-init~13218 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=99f93dd3a502568441da3db04ddf0655a2e38c24;p=platform%2Fupstream%2Fllvm.git [rs4gc] avoid insert base computation instructions for deopt uses If we have a value live over a call which is used for deopt at the call, we know that the value must be a base pointer. We can avoid potentially inserting IR to materialize a base for this value. In it's current form, this is mostly a compile time optimization. Building the base pointer graph (and then optimizing it away again) is a relatively expensive operation. We also sometimes end up with better codegen in practice - due to failures in optimizing away the inserted base pointer propogation - but those are optimization bugs we're fixing concurrently. The alternative to this would be to extend the base pointer inference with the ability to generally reuse multiple-base input instructions (phis and selects). That's somewhat invasive and complicated, so we're defering it a bit longer. Differential Revision: https://reviews.llvm.org/D97885 --- diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp index b783055..4f98fff 100644 --- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp +++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp @@ -1236,7 +1236,20 @@ static void findBasePointers(DominatorTree &DT, DefiningValueMapTy &DVCache, CallBase *Call, PartiallyConstructedSafepointRecord &result) { MapVector PointerToBase; - findBasePointers(result.LiveSet, PointerToBase, &DT, DVCache); + StatepointLiveSetTy PotentiallyDerivedPointers = result.LiveSet; + // We assume that all pointers passed to deopt are base pointers; as an + // optimization, we can use this to avoid seperately materializing the base + // pointer graph. This is only relevant since we're very conservative about + // generating new conflict nodes during base pointer insertion. If we were + // smarter there, this would be irrelevant. + if (auto Opt = Call->getOperandBundle(LLVMContext::OB_deopt)) + for (Value *V : Opt->Inputs) { + if (!PotentiallyDerivedPointers.count(V)) + continue; + PotentiallyDerivedPointers.remove(V); + PointerToBase[V] = V; + } + findBasePointers(PotentiallyDerivedPointers, PointerToBase, &DT, DVCache); if (PrintBasePointers) { errs() << "Base Pairs (w/o Relocation):\n"; diff --git a/llvm/test/Transforms/RewriteStatepointsForGC/base-pointers.ll b/llvm/test/Transforms/RewriteStatepointsForGC/base-pointers.ll index 46a73c2..752e866 100644 --- a/llvm/test/Transforms/RewriteStatepointsForGC/base-pointers.ll +++ b/llvm/test/Transforms/RewriteStatepointsForGC/base-pointers.ll @@ -152,4 +152,24 @@ next: ; preds = %merge ret i64 addrspace(1)* %bdv } +; We know from the deopt use that %bdv must be a base value, and as +; result can avoid materializing the extra copy of the BDV phi node. +; (Even without a general forward analysis) +define i64 addrspace(1)* @test6(i1 %cnd, i64 addrspace(1)* %obj, i64 addrspace(1)* %obj2) gc "statepoint-example" { +; CHECK-LABEL: @test6 +entry: + br label %merge + +merge: ; preds = %merge, %entry +; CHECK-LABEL: merge: +; CHECK-NEXT: phi +; CHECK-NEXT: br i1 + %bdv = phi i64 addrspace(1)* [ %obj, %entry ], [ %obj2, %merge ] + br i1 %cnd, label %merge, label %next + +next: ; preds = %merge + call void @foo() [ "deopt"(i64 addrspace(1)* %bdv) ] + ret i64 addrspace(1)* %bdv +} + declare void @foo() diff --git a/llvm/test/Transforms/RewriteStatepointsForGC/scalar-base-vector.ll b/llvm/test/Transforms/RewriteStatepointsForGC/scalar-base-vector.ll index 2d3eb62..82768f2 100644 --- a/llvm/test/Transforms/RewriteStatepointsForGC/scalar-base-vector.ll +++ b/llvm/test/Transforms/RewriteStatepointsForGC/scalar-base-vector.ll @@ -147,24 +147,20 @@ define void @test6() gc "statepoint-example" { ; CHECK-NEXT: bb: ; CHECK-NEXT: br label [[HEADER:%.*]] ; CHECK: header: -; CHECK-NEXT: [[TMP_BASE:%.*]] = phi i8 addrspace(1)* [ [[TMP6_BASE:%.*]], [[LATCH:%.*]] ], [ null, [[BB:%.*]] ], !is_base_value !0 -; CHECK-NEXT: [[TMP:%.*]] = phi i8 addrspace(1)* [ [[TMP6:%.*]], [[LATCH]] ], [ undef, [[BB]] ] +; CHECK-NEXT: [[TMP:%.*]] = phi i8 addrspace(1)* [ [[TMP6:%.*]], [[LATCH:%.*]] ], [ undef, [[BB:%.*]] ] ; CHECK-NEXT: br label [[BB10:%.*]] ; CHECK: bb10: -; CHECK-NEXT: [[STATEPOINT_TOKEN:%.*]] = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void ()* @spam, i32 0, i32 0, i32 0, i32 0) [ "deopt"(i8 addrspace(1)* [[TMP]]), "gc-live"(i8 addrspace(1)* [[TMP]], i8 addrspace(1)* [[TMP_BASE]]) ] -; CHECK-NEXT: [[TMP_RELOCATED:%.*]] = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token [[STATEPOINT_TOKEN]], i32 1, i32 0) -; CHECK-NEXT: [[TMP_BASE_RELOCATED:%.*]] = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token [[STATEPOINT_TOKEN]], i32 1, i32 1) +; CHECK-NEXT: [[STATEPOINT_TOKEN:%.*]] = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void ()* @spam, i32 0, i32 0, i32 0, i32 0) [ "deopt"(i8 addrspace(1)* [[TMP]]), "gc-live"(i8 addrspace(1)* [[TMP]]) ] +; CHECK-NEXT: [[TMP_RELOCATED:%.*]] = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token [[STATEPOINT_TOKEN]], i32 0, i32 0) ; CHECK-NEXT: br label [[BB25:%.*]] ; CHECK: bb25: ; CHECK-NEXT: [[STATEPOINT_TOKEN1:%.*]] = call token (i64, i32, <2 x i8 addrspace(1)*> ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_v2p1i8f(i64 2882400000, i32 0, <2 x i8 addrspace(1)*> ()* @baz, i32 0, i32 0, i32 0, i32 0) ; CHECK-NEXT: [[TMP262:%.*]] = call <2 x i8 addrspace(1)*> @llvm.experimental.gc.result.v2p1i8(token [[STATEPOINT_TOKEN1]]) -; CHECK-NEXT: [[BASE_EE:%.*]] = extractelement <2 x i8 addrspace(1)*> [[TMP262]], i32 0, !is_base_value !0 ; CHECK-NEXT: [[TMP27:%.*]] = extractelement <2 x i8 addrspace(1)*> [[TMP262]], i32 0 ; CHECK-NEXT: br i1 undef, label [[BB7:%.*]], label [[LATCH]] ; CHECK: bb7: ; CHECK-NEXT: br label [[LATCH]] ; CHECK: latch: -; CHECK-NEXT: [[TMP6_BASE]] = phi i8 addrspace(1)* [ [[BASE_EE]], [[BB25]] ], [ [[BASE_EE]], [[BB7]] ], !is_base_value !0 ; CHECK-NEXT: [[TMP6]] = phi i8 addrspace(1)* [ [[TMP27]], [[BB25]] ], [ [[TMP27]], [[BB7]] ] ; CHECK-NEXT: br label [[HEADER]] ;