llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-llvm-transforms Author: Ryotaro Kasuga (kasuga-fj) <details> <summary>Changes</summary> This patch fixes the issue pointed out in https://github.com/llvm/llvm-project/pull/200828#issuecomment-4593914293. As demonstrated by the test cases added in #<!-- -->201331, it is not legal to interchange loops that contain call instructions which may diverge. This patch adds an additional check and bails out early when we cannot prove that a call instruction in the loops doesn't diverge. --- Full diff: https://github.com/llvm/llvm-project/pull/201348.diff 2 Files Affected: - (modified) llvm/lib/Transforms/Scalar/LoopInterchange.cpp (+4-2) - (modified) llvm/test/Transforms/LoopInterchange/function-attr.ll (+16-40) ``````````diff diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp index 707d44c8411e8..df46a37be655a 100644 --- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp @@ -1474,8 +1474,10 @@ bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId, for (auto *BB : OuterLoop->blocks()) for (Instruction &I : *BB) if (CallInst *CI = dyn_cast<CallInst>(&I)) { - // Functions which don't access memory do not prevent interchanging. - if (CI->doesNotAccessMemory() || isa<PseudoProbeInst>(CI)) + // Functions which don't access memory and doesn't diverge do not + // prevent interchanging. + if ((CI->doesNotAccessMemory() && !CI->mayHaveSideEffects()) || + isa<PseudoProbeInst>(CI)) continue; LLVM_DEBUG( dbgs() << "Loops with call instructions cannot be interchanged " diff --git a/llvm/test/Transforms/LoopInterchange/function-attr.ll b/llvm/test/Transforms/LoopInterchange/function-attr.ll index a26d308b4eb6b..6642047ce5598 100644 --- a/llvm/test/Transforms/LoopInterchange/function-attr.ll +++ b/llvm/test/Transforms/LoopInterchange/function-attr.ll @@ -134,43 +134,31 @@ exit: ; Interchanging the loops changes the semantics of the program, e.g., `A[0][9]` ; will be overwritten in the original code, but not in the interchanged one. ; -; FIXME: Currently the loops are interchanged. -; define void @call_throw_exception(ptr %A) { ; CHECK-LABEL: define void @call_throw_exception( ; CHECK-SAME: ptr [[A:%.*]]) { -; CHECK-NEXT: [[ENTRY:.*:]] -; CHECK-NEXT: br label %[[INNER_HEADER_PREHEADER:.*]] -; CHECK: [[OUTER_HEADER_PREHEADER:.*]]: -; CHECK-NEXT: br label %[[OUTER_HEADER:.*]] -; CHECK: [[OUTER_HEADER]]: -; CHECK-NEXT: [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ], [ 0, %[[OUTER_HEADER_PREHEADER]] ] -; CHECK-NEXT: br label %[[INNER_HEADER_SPLIT:.*]] -; CHECK: [[INNER_HEADER_PREHEADER]]: +; CHECK-NEXT: [[INNER_HEADER_PREHEADER:.*]]: ; CHECK-NEXT: br label %[[INNER_HEADER:.*]] ; CHECK: [[INNER_HEADER]]: -; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[TMP0:%.*]], %[[INNER_LATCH_SPLIT:.*]] ], [ 0, %[[INNER_HEADER_PREHEADER]] ] -; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER]] -; CHECK: [[INNER_HEADER_SPLIT]]: +; CHECK-NEXT: [[I:%.*]] = phi i64 [ 0, %[[INNER_HEADER_PREHEADER]] ], [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ] +; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER:.*]] +; CHECK: [[OUTER_HEADER_PREHEADER]]: +; CHECK-NEXT: [[J:%.*]] = phi i64 [ 0, %[[INNER_HEADER]] ], [ [[TMP0:%.*]], %[[INNER_LATCH:.*]] ] ; CHECK-NEXT: [[GEP:%.*]] = getelementptr [10 x i8], ptr [[A]], i64 [[J]], i64 [[I]] ; CHECK-NEXT: store i8 0, ptr [[GEP]], align 1 ; CHECK-NEXT: [[COND:%.*]] = icmp eq i64 [[J]], 1 -; CHECK-NEXT: br i1 [[COND]], label %[[UNWIND:.*]], label %[[INNER_LATCH:.*]] +; CHECK-NEXT: br i1 [[COND]], label %[[UNWIND:.*]], label %[[INNER_LATCH]] ; CHECK: [[UNWIND]]: ; CHECK-NEXT: call void @throw_exception() ; CHECK-NEXT: br label %[[INNER_LATCH]] ; CHECK: [[INNER_LATCH]]: -; CHECK-NEXT: [[J_NEXT:%.*]] = add i64 [[J]], 1 -; CHECK-NEXT: [[EC_INNER:%.*]] = icmp eq i64 [[J_NEXT]], 10 -; CHECK-NEXT: br label %[[OUTER_LATCH]] -; CHECK: [[INNER_LATCH_SPLIT]]: ; CHECK-NEXT: [[TMP0]] = add i64 [[J]], 1 ; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[TMP0]], 10 -; CHECK-NEXT: br i1 [[TMP1]], label %[[EXIT:.*]], label %[[INNER_HEADER]] +; CHECK-NEXT: br i1 [[TMP1]], label %[[OUTER_LATCH]], label %[[OUTER_HEADER_PREHEADER]] ; CHECK: [[OUTER_LATCH]]: ; CHECK-NEXT: [[I_NEXT]] = add i64 [[I]], 1 ; CHECK-NEXT: [[EC_OUTER:%.*]] = icmp eq i64 [[I_NEXT]], 10 -; CHECK-NEXT: br i1 [[EC_OUTER]], label %[[INNER_LATCH_SPLIT]], label %[[OUTER_HEADER]] +; CHECK-NEXT: br i1 [[EC_OUTER]], label %[[EXIT:.*]], label %[[INNER_HEADER]] ; CHECK: [[EXIT]]: ; CHECK-NEXT: ret void ; @@ -219,42 +207,30 @@ exit: ; present in the original code (e.g., `A[9999]`) which results in UB. Thus we ; cannot interchange the loops. ; -; FIXEM: Currently the loops are deemed legal to interchange. -; define void @call_not_return() { ; CHECK-LABEL: define void @call_not_return() { -; CHECK-NEXT: [[ENTRY:.*:]] -; CHECK-NEXT: br label %[[OUTER_HEADER:.*]] -; CHECK: [[OUTER_HEADER_PREHEADER:.*]]: -; CHECK-NEXT: br label %[[INNER_HEADER:.*]] -; CHECK: [[INNER_HEADER]]: -; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ], [ 0, %[[OUTER_HEADER_PREHEADER]] ] -; CHECK-NEXT: br label %[[INNER_HEADER_SPLIT:.*]] -; CHECK: [[OUTER_HEADER]]: +; CHECK-NEXT: [[OUTER_HEADER:.*]]: ; CHECK-NEXT: br label %[[INNER_HEADER1:.*]] ; CHECK: [[INNER_HEADER1]]: -; CHECK-NEXT: [[I:%.*]] = phi i64 [ [[TMP0:%.*]], %[[INNER_LATCH_SPLIT:.*]] ], [ 0, %[[OUTER_HEADER]] ] -; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER]] -; CHECK: [[INNER_HEADER_SPLIT]]: +; CHECK-NEXT: [[J:%.*]] = phi i64 [ 0, %[[OUTER_HEADER]] ], [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ] +; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER:.*]] +; CHECK: [[OUTER_HEADER_PREHEADER]]: +; CHECK-NEXT: [[I:%.*]] = phi i64 [ 0, %[[INNER_HEADER1]] ], [ [[TMP0:%.*]], %[[INNER_LATCH:.*]] ] ; CHECK-NEXT: [[GEP:%.*]] = getelementptr [10 x i8], ptr @ARR_100, i64 [[J]], i64 [[I]] ; CHECK-NEXT: store i8 0, ptr [[GEP]], align 1 ; CHECK-NEXT: [[COND:%.*]] = icmp eq i64 [[I]], 1 -; CHECK-NEXT: br i1 [[COND]], label %[[TRAP:.*]], label %[[INNER_LATCH:.*]] +; CHECK-NEXT: br i1 [[COND]], label %[[TRAP:.*]], label %[[INNER_LATCH]] ; CHECK: [[TRAP]]: ; CHECK-NEXT: call void @not_return() ; CHECK-NEXT: br label %[[INNER_LATCH]] ; CHECK: [[INNER_LATCH]]: -; CHECK-NEXT: [[J_NEXT:%.*]] = add i64 [[I]], 1 -; CHECK-NEXT: [[EC_INNER:%.*]] = icmp eq i64 [[J_NEXT]], 10 -; CHECK-NEXT: br label %[[OUTER_LATCH]] -; CHECK: [[INNER_LATCH_SPLIT]]: ; CHECK-NEXT: [[TMP0]] = add i64 [[I]], 1 ; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[TMP0]], 10 -; CHECK-NEXT: br i1 [[TMP1]], label %[[EXIT:.*]], label %[[INNER_HEADER1]] +; CHECK-NEXT: br i1 [[TMP1]], label %[[OUTER_LATCH]], label %[[OUTER_HEADER_PREHEADER]] ; CHECK: [[OUTER_LATCH]]: ; CHECK-NEXT: [[I_NEXT]] = add i64 [[J]], 1 ; CHECK-NEXT: [[EC_OUTER:%.*]] = icmp eq i64 [[I_NEXT]], 1000 -; CHECK-NEXT: br i1 [[EC_OUTER]], label %[[INNER_LATCH_SPLIT]], label %[[INNER_HEADER]] +; CHECK-NEXT: br i1 [[EC_OUTER]], label %[[EXIT:.*]], label %[[INNER_HEADER1]] ; CHECK: [[EXIT]]: ; CHECK-NEXT: ret void ; `````````` </details> https://github.com/llvm/llvm-project/pull/201348 _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
