From 10084675235db2bc5fd46805688e5897a801ad2b Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Wed, 29 Jul 2015 15:38:37 +0000 Subject: [PATCH] Merging r243500: (conflicts resolved manually since the branch doesn't have r243293) ------------------------------------------------------------------------ r243500 | spatel | 2015-07-28 16:28:22 -0700 (Tue, 28 Jul 2015) | 16 lines ignore duplicate divisor uses when transforming into reciprocal multiplies (PR24141) PR24141: https://llvm.org/bugs/show_bug.cgi?id=24141 contains a test case where we have duplicate entries in a node's uses() list. After r241826, we use CombineTo() to delete dead nodes when combining the uses into reciprocal multiplies, but this fails if we encounter the just-deleted node again in the list. The solution in this patch is to not add duplicate entries to the list of users that we will subsequently iterate over. For the test case, this avoids triggering the combine divisors logic entirely because there really is only one user of the divisor. Differential Revision: http://reviews.llvm.org/D11345 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_37@243524 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 8 ++++---- test/CodeGen/X86/fdiv-combine.ll | 19 +++++++++++++++++++ 2 files changed, 23 insertions(+), 4 deletions(-) diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 52d620b1d54..3b29306bb54 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -8365,12 +8365,12 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) { if (N0CFP && N0CFP->isExactlyValue(1.0)) return SDValue(); - SmallVector Users; // Find all FDIV users of the same divisor. - for (auto *U : N1->uses()) { + // Use a set because duplicates may be present in the user list. + SetVector Users; + for (auto *U : N1->uses()) if (U->getOpcode() == ISD::FDIV && U->getOperand(1) == N1) - Users.push_back(U); - } + Users.insert(U); if (TLI.combineRepeatedFPDivisors(Users.size())) { SDValue FPOne = DAG.getConstantFP(1.0, DL, VT); diff --git a/test/CodeGen/X86/fdiv-combine.ll b/test/CodeGen/X86/fdiv-combine.ll index 34eac62e367..b65e9d01ab8 100644 --- a/test/CodeGen/X86/fdiv-combine.ll +++ b/test/CodeGen/X86/fdiv-combine.ll @@ -44,5 +44,24 @@ define double @div3_arcp(double %x, double %y, double %z) #0 { ret double %ret } +define void @PR24141() #0 { +; CHECK-LABEL: PR24141: +; CHECK: callq +; CHECK-NEXT: divsd +; CHECK-NEXT: jmp +entry: + br label %while.body + +while.body: + %x.0 = phi double [ undef, %entry ], [ %div, %while.body ] + %call = call { double, double } @g(double %x.0) + %xv0 = extractvalue { double, double } %call, 0 + %xv1 = extractvalue { double, double } %call, 1 + %div = fdiv double %xv0, %xv1 + br label %while.body +} + +declare { double, double } @g(double) + ; FIXME: If the backend understands 'arcp', then this attribute is unnecessary. attributes #0 = { "unsafe-fp-math"="true" }