From 00edf39b3447db1b8dc0030d716ef70675f55755 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Mon, 10 Aug 2009 23:43:19 +0000 Subject: [PATCH] Fix a bug in the DAGCombiner's handling of multiple linked MERGE_VALUES nodes. Replacing the result values with the operands in one MERGE_VALUES node may cause another MERGE_VALUES node be CSE'd with the first one, and bring its uses along, so that the first one isn't dead, as this code expects. Fix this by iterating until the node is really dead. This fixes PR4699. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78619 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 11 ++++++++--- test/CodeGen/X86/extract-extract.ll | 24 ++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 3 deletions(-) create mode 100644 test/CodeGen/X86/extract-extract.ll diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 42d163f79b1..d4d13884cb0 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -924,9 +924,14 @@ SDValue DAGCombiner::visitTokenFactor(SDNode *N) { /// MERGE_VALUES can always be eliminated. SDValue DAGCombiner::visitMERGE_VALUES(SDNode *N) { WorkListRemover DeadNodes(*this); - for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) - DAG.ReplaceAllUsesOfValueWith(SDValue(N, i), N->getOperand(i), - &DeadNodes); + // Replacing results may cause a different MERGE_VALUES to suddenly + // be CSE'd with N, and carry its uses with it. Iterate until no + // uses remain, to ensure that the node can be safely deleted. + do { + for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) + DAG.ReplaceAllUsesOfValueWith(SDValue(N, i), N->getOperand(i), + &DeadNodes); + } while (!N->use_empty()); removeFromWorkList(N); DAG.DeleteNode(N); return SDValue(N, 0); // Return N so it doesn't get rechecked! diff --git a/test/CodeGen/X86/extract-extract.ll b/test/CodeGen/X86/extract-extract.ll new file mode 100644 index 00000000000..1e0ce9a3244 --- /dev/null +++ b/test/CodeGen/X86/extract-extract.ll @@ -0,0 +1,24 @@ +; RUN: llvm-as < %s | llc -march=x86 >/dev/null +; PR4699 + +; Handle this extractvalue-of-extractvalue case without getting in +; trouble with CSE in DAGCombine. + + %cc = type { %crd } + %cr = type { i32 } + %crd = type { i64, %cr* } + %pp = type { %cc } + +define fastcc void @foo(%pp* nocapture byval %p_arg) { +entry: + %tmp2 = getelementptr %pp* %p_arg, i64 0, i32 0 ; <%cc*> [#uses= + %tmp3 = load %cc* %tmp2 ; <%cc> [#uses=1] + %tmp34 = extractvalue %cc %tmp3, 0 ; <%crd> [#uses=1] + %tmp345 = extractvalue %crd %tmp34, 0 ; [#uses=1] + %.ptr.i = load %cr** undef ; <%cr*> [#uses=0] + %tmp15.i = shl i64 %tmp345, 3 ; [#uses=0] + store %cr* undef, %cr** undef + ret void +} + + -- 2.34.1