Author: Philip Reames Date: 2020-02-26T16:13:01+01:00 New Revision: 48d24465668b268ec0aa39b62cabab5ee50e961d
URL: https://github.com/llvm/llvm-project/commit/48d24465668b268ec0aa39b62cabab5ee50e961d DIFF: https://github.com/llvm/llvm-project/commit/48d24465668b268ec0aa39b62cabab5ee50e961d.diff LOG: Revert "[LICM] Support hosting of dynamic allocas out of loops" This reverts commit 8d22100f66c4170510c6ff028c60672acfe1cff9. There was a functional regression reported (https://bugs.llvm.org/show_bug.cgi?id=44996). I'm not actually sure the patch is wrong, but I don't have time to investigate currently, and this line of work isn't something I'm likely to get back to quickly. (cherry picked from commit 14845b2c459021e3dbf2ead52d707d4a7db40cbb) Added: Modified: llvm/lib/Transforms/Scalar/LICM.cpp Removed: llvm/test/Transforms/LICM/hoist-alloca.ll ################################################################################ diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp index eb023d49b0a3..a1c012fddde3 100644 --- a/llvm/lib/Transforms/Scalar/LICM.cpp +++ b/llvm/lib/Transforms/Scalar/LICM.cpp @@ -790,41 +790,6 @@ class ControlFlowHoister { }; } // namespace - -/// Return true if we know how to rewrite all uses of the given alloca after -/// hoisting it out of the loop. The main concerns are a) potential captures -/// and b) invariant.start markers which don't capture, but are no longer -/// valid w/o a corresponding invariant.end. -static bool canRewriteUsesOfAlloca(AllocaInst &AI) { - // TODO: This looks a lot like capture tracking, but we need to remove any - // invariant starts if we extend the lifetime of the alloca by hoisting it. - // We should probably refactor capture tracking into a form which allows us - // to reuse the relevant bits and remove the duplicated logic here. - - SmallVector<Use *, 16> Worklist; - for (Use &U : AI.uses()) - Worklist.push_back(&U); - - unsigned NumUsesExplored = 0; - while (!Worklist.empty()) { - Use *U = Worklist.pop_back_val(); - Instruction *I = cast<Instruction>(U->getUser()); - NumUsesExplored++; - if (NumUsesExplored > DefaultMaxUsesToExplore) - return false; - // Non capturing, terminating uses - if (isa<LoadInst>(I) || - (isa<StoreInst>(I) && U->getOperandNo() == 1)) - continue; - // Non capturing, non-terminating - if (!isa<BitCastInst>(I) && !isa<GetElementPtrInst>(I)) - return false; - for (Use &U : I->uses()) - Worklist.push_back(&U); - } - return true; -} - /// Walk the specified region of the CFG (defined by all blocks dominated by /// the specified block, and that are in the current loop) in depth first /// order w.r.t the DominatorTree. This allows us to visit definitions before @@ -945,16 +910,6 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI, continue; } - if (isa<AllocaInst>(&I) && - SafetyInfo->isGuaranteedToExecute(I, DT, CurLoop) && - canRewriteUsesOfAlloca(cast<AllocaInst>(I))) { - hoist(I, DT, CurLoop, CFH.getOrCreateHoistedBlock(BB), SafetyInfo, - MSSAU, SE, ORE); - HoistedInstructions.push_back(&I); - Changed = true; - continue; - } - if (PHINode *PN = dyn_cast<PHINode>(&I)) { if (CFH.canHoistPHI(PN)) { // Redirect incoming blocks first to ensure that we create hoisted diff --git a/llvm/test/Transforms/LICM/hoist-alloca.ll b/llvm/test/Transforms/LICM/hoist-alloca.ll deleted file mode 100644 index 8e4debac2838..000000000000 --- a/llvm/test/Transforms/LICM/hoist-alloca.ll +++ /dev/null @@ -1,168 +0,0 @@ -; NOTE: Assertions have been autogenerated by utils/update_test_checks.py -; RUN: opt -S -licm < %s | FileCheck %s - -@G = external global i64 - -define void @test(i64 %n) { -; CHECK-LABEL: @test( -; CHECK-NEXT: entry: -; CHECK-NEXT: [[A:%.*]] = alloca i64 -; CHECK-NEXT: [[VAL:%.*]] = load i64, i64* [[A]] -; CHECK-NEXT: store i64 [[VAL]], i64* @G -; CHECK-NEXT: br label [[FOR_BODY:%.*]] -; CHECK: for.body: -; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ] -; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1 -; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[IV]], [[N:%.*]] -; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[EXIT:%.*]] -; CHECK: exit: -; CHECK-NEXT: ret void -; -entry: - br label %for.body - -for.body: - %iv = phi i64 [ %iv.next, %for.body ], [ 0, %entry ] - %a = alloca i64 - %val = load i64, i64* %a - store i64 %val, i64* @G - %iv.next = add nuw nsw i64 %iv, 1 - %exitcond = icmp ult i64 %iv, %n - br i1 %exitcond, label %for.body, label %exit -exit: - ret void -} - -define void @test2(i64 %n) { -; CHECK-LABEL: @test2( -; CHECK-NEXT: entry: -; CHECK-NEXT: [[A:%.*]] = alloca i64 -; CHECK-NEXT: br label [[FOR_BODY:%.*]] -; CHECK: for.body: -; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ] -; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1 -; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[IV]], [[N:%.*]] -; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[EXIT:%.*]] -; CHECK: exit: -; CHECK-NEXT: [[IV_LCSSA:%.*]] = phi i64 [ [[IV]], [[FOR_BODY]] ] -; CHECK-NEXT: store i64 [[IV_LCSSA]], i64* [[A]], align 4 -; CHECK-NEXT: ret void -; -entry: - br label %for.body - -for.body: - %iv = phi i64 [ %iv.next, %for.body ], [ 0, %entry ] - %a = alloca i64 - store i64 %iv, i64* %a - %iv.next = add nuw nsw i64 %iv, 1 - %exitcond = icmp ult i64 %iv, %n - br i1 %exitcond, label %for.body, label %exit -exit: - ret void -} - - -define void @test3(i64 %n) { -; CHECK-LABEL: @test3( -; CHECK-NEXT: entry: -; CHECK-NEXT: [[A:%.*]] = alloca i64 -; CHECK-NEXT: [[A_I8:%.*]] = bitcast i64* [[A]] to i8* -; CHECK-NEXT: [[A_OFFSET:%.*]] = getelementptr i8, i8* [[A_I8]], i64 4 -; CHECK-NEXT: store i8 0, i8* [[A_OFFSET]] -; CHECK-NEXT: br label [[FOR_BODY:%.*]] -; CHECK: for.body: -; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ] -; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1 -; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[IV]], [[N:%.*]] -; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[EXIT:%.*]] -; CHECK: exit: -; CHECK-NEXT: ret void -; -entry: - br label %for.body - -for.body: - %iv = phi i64 [ %iv.next, %for.body ], [ 0, %entry ] - %a = alloca i64 - %a.i8 = bitcast i64* %a to i8* - %a.offset = getelementptr i8, i8* %a.i8, i64 4 - store i8 0, i8* %a.offset - %iv.next = add nuw nsw i64 %iv, 1 - %exitcond = icmp ult i64 %iv, %n - br i1 %exitcond, label %for.body, label %exit -exit: - ret void -} - -; This example is subtle. Because the dynamic alloca isn't reclaimed until -; end of function scope, the captured value can legally point to a dynamic -; alloca stack region from a previous iteration. -define void @test4(i64 %n) { -; CHECK-LABEL: @test4( -; CHECK-NEXT: entry: -; CHECK-NEXT: br label [[FOR_BODY:%.*]] -; CHECK: for.body: -; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ] -; CHECK-NEXT: [[A:%.*]] = alloca i64 -; CHECK-NEXT: store i64 [[IV]], i64* [[A]] -; CHECK-NEXT: call void @capture(i64* [[A]]) -; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1 -; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[IV]], [[N:%.*]] -; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[EXIT:%.*]] -; CHECK: exit: -; CHECK-NEXT: ret void -; -entry: - br label %for.body - -for.body: - %iv = phi i64 [ %iv.next, %for.body ], [ 0, %entry ] - %a = alloca i64 - store i64 %iv, i64* %a - %a.i8 = bitcast i64* %a to i8* - call void @capture(i64* %a) - %iv.next = add nuw nsw i64 %iv, 1 - %exitcond = icmp ult i64 %iv, %n - br i1 %exitcond, label %for.body, label %exit -exit: - ret void -} -declare void @capture(i64* %a) - - -; TODO: not yet handled -define void @test5(i64 %n) { -; CHECK-LABEL: @test5( -; CHECK-NEXT: entry: -; CHECK-NEXT: br label [[FOR_BODY:%.*]] -; CHECK: for.body: -; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ] -; CHECK-NEXT: [[A:%.*]] = alloca i64 -; CHECK-NEXT: store i64 [[IV]], i64* [[A]] -; CHECK-NEXT: [[A_I8:%.*]] = bitcast i64* [[A]] to i8* -; CHECK-NEXT: [[TMP0:%.*]] = call {}* @llvm.invariant.start.p0i8(i64 8, i8* [[A_I8]]) -; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1 -; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[IV]], [[N:%.*]] -; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[EXIT:%.*]] -; CHECK: exit: -; CHECK-NEXT: ret void -; -entry: - br label %for.body - -for.body: - %iv = phi i64 [ %iv.next, %for.body ], [ 0, %entry ] - %a = alloca i64 - store i64 %iv, i64* %a - %a.i8 = bitcast i64* %a to i8* - call {}* @llvm.invariant.start.p0i8(i64 8, i8* %a.i8) - %iv.next = add nuw nsw i64 %iv, 1 - %exitcond = icmp ult i64 %iv, %n - br i1 %exitcond, label %for.body, label %exit -exit: - ret void -} - -declare {}* @llvm.invariant.start.p0i8(i64, i8* nocapture) nounwind readonly - _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
