From 00816714f96505c59c236f3f0fd2eb815c57f674 Mon Sep 17 00:00:00 2001 From: Craig Topper Date: Sat, 22 Oct 2022 18:54:48 -0700 Subject: [PATCH] [DAGCombiner][RISCV] Make foldBinOpIntoSelect work correctly with opaque constants. The CanFoldNonConst doesn't work correctly with opaque constants because getNode won't constant fold constants if one is opaque. Even if the operation is AND/OR. This can lead to infinite loops. This patch does the folding manually in the DAGCombine. Alternatively, we could improve getNode but that seemed likely to have bigger impact and possibly increase compile time for the additional checks. We wouldn't want to directly constant fold because we need to preserve the opaque flag. Fixes PR58511. Reviewed By: spatel Differential Revision: https://reviews.llvm.org/D136472 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 52 +++++++++++------ llvm/test/CodeGen/RISCV/pr58511.ll | 83 +++++++++++++++++++++++++++ 2 files changed, 118 insertions(+), 17 deletions(-) create mode 100644 llvm/test/CodeGen/RISCV/pr58511.ll diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 38cd6b5..a4c04b52 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2271,8 +2271,8 @@ SDValue DAGCombiner::foldBinOpIntoSelect(SDNode *BO) { // or X, (select Cond, -1, 0) --> select Cond, -1, X bool CanFoldNonConst = (BinOpcode == ISD::AND || BinOpcode == ISD::OR) && - (isNullOrNullSplat(CT) || isAllOnesOrAllOnesSplat(CT)) && - (isNullOrNullSplat(CF) || isAllOnesOrAllOnesSplat(CF)); + ((isNullOrNullSplat(CT) && isAllOnesOrAllOnesSplat(CF)) || + (isNullOrNullSplat(CF) && isAllOnesOrAllOnesSplat(CT))); SDValue CBO = BO->getOperand(SelOpNo ^ 1); if (!CanFoldNonConst && @@ -2280,23 +2280,41 @@ SDValue DAGCombiner::foldBinOpIntoSelect(SDNode *BO) { !DAG.isConstantFPBuildVectorOrConstantFP(CBO)) return SDValue(); - // We have a select-of-constants followed by a binary operator with a - // constant. Eliminate the binop by pulling the constant math into the select. - // Example: add (select Cond, CT, CF), CBO --> select Cond, CT + CBO, CF + CBO SDLoc DL(Sel); - SDValue NewCT = SelOpNo ? DAG.getNode(BinOpcode, DL, VT, CBO, CT) - : DAG.getNode(BinOpcode, DL, VT, CT, CBO); - if (!CanFoldNonConst && !NewCT.isUndef() && - !isConstantOrConstantVector(NewCT, true) && - !DAG.isConstantFPBuildVectorOrConstantFP(NewCT)) - return SDValue(); + SDValue NewCT, NewCF; - SDValue NewCF = SelOpNo ? DAG.getNode(BinOpcode, DL, VT, CBO, CF) - : DAG.getNode(BinOpcode, DL, VT, CF, CBO); - if (!CanFoldNonConst && !NewCF.isUndef() && - !isConstantOrConstantVector(NewCF, true) && - !DAG.isConstantFPBuildVectorOrConstantFP(NewCF)) - return SDValue(); + if (CanFoldNonConst) { + // If CBO is an opaque constant, we can't rely on getNode to constant fold. + if ((BinOpcode == ISD::AND && isNullOrNullSplat(CT)) || + (BinOpcode == ISD::OR && isAllOnesOrAllOnesSplat(CT))) + NewCT = CT; + else + NewCT = CBO; + + if ((BinOpcode == ISD::AND && isNullOrNullSplat(CF)) || + (BinOpcode == ISD::OR && isAllOnesOrAllOnesSplat(CF))) + NewCF = CF; + else + NewCF = CBO; + } else { + // We have a select-of-constants followed by a binary operator with a + // constant. Eliminate the binop by pulling the constant math into the + // select. Example: add (select Cond, CT, CF), CBO --> select Cond, CT + + // CBO, CF + CBO + NewCT = SelOpNo ? DAG.getNode(BinOpcode, DL, VT, CBO, CT) + : DAG.getNode(BinOpcode, DL, VT, CT, CBO); + if (!CanFoldNonConst && !NewCT.isUndef() && + !isConstantOrConstantVector(NewCT, true) && + !DAG.isConstantFPBuildVectorOrConstantFP(NewCT)) + return SDValue(); + + NewCF = SelOpNo ? DAG.getNode(BinOpcode, DL, VT, CBO, CF) + : DAG.getNode(BinOpcode, DL, VT, CF, CBO); + if (!CanFoldNonConst && !NewCF.isUndef() && + !isConstantOrConstantVector(NewCF, true) && + !DAG.isConstantFPBuildVectorOrConstantFP(NewCF)) + return SDValue(); + } SDValue SelectOp = DAG.getSelect(DL, VT, Sel.getOperand(0), NewCT, NewCF); SelectOp->setFlags(BO->getFlags()); diff --git a/llvm/test/CodeGen/RISCV/pr58511.ll b/llvm/test/CodeGen/RISCV/pr58511.ll new file mode 100644 index 0000000..ed520af --- /dev/null +++ b/llvm/test/CodeGen/RISCV/pr58511.ll @@ -0,0 +1,83 @@ +; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py +; RUN: llc < %s -mtriple=riscv64 | FileCheck %s + +define i32 @f(i1 %0, i32 %1, ptr %2) { +; CHECK-LABEL: f: +; CHECK: # %bb.0: # %BB +; CHECK-NEXT: slliw a3, a1, 11 +; CHECK-NEXT: slliw a1, a1, 12 +; CHECK-NEXT: subw a1, a1, a3 +; CHECK-NEXT: andi a0, a0, 1 +; CHECK-NEXT: neg a0, a0 +; CHECK-NEXT: lui a3, 1 +; CHECK-NEXT: addiw a3, a3, -2048 +; CHECK-NEXT: or a0, a0, a3 +; CHECK-NEXT: sw a1, 0(a2) +; CHECK-NEXT: ret +BB: + %I = select i1 %0, i32 -1, i32 0 + %I1 = mul i32 %1, 2048 + %I2 = or i32 2048, %I + store i32 %I1, ptr %2 + ret i32 %I2 +} + +define i32 @g(i1 %0, i32 %1, ptr %2) { +; CHECK-LABEL: g: +; CHECK: # %bb.0: # %BB +; CHECK-NEXT: slliw a3, a1, 11 +; CHECK-NEXT: slliw a1, a1, 12 +; CHECK-NEXT: subw a1, a1, a3 +; CHECK-NEXT: andi a0, a0, 1 +; CHECK-NEXT: addi a0, a0, -1 +; CHECK-NEXT: lui a3, 1 +; CHECK-NEXT: addiw a3, a3, -2048 +; CHECK-NEXT: or a0, a0, a3 +; CHECK-NEXT: sw a1, 0(a2) +; CHECK-NEXT: ret +BB: + %I = select i1 %0, i32 0, i32 -1 + %I1 = mul i32 %1, 2048 + %I2 = or i32 2048, %I + store i32 %I1, ptr %2 + ret i32 %I2 +} + +define i32 @h(i1 %0, i32 %1, ptr %2) { +; CHECK-LABEL: h: +; CHECK: # %bb.0: # %BB +; CHECK-NEXT: slliw a3, a1, 11 +; CHECK-NEXT: slliw a1, a1, 12 +; CHECK-NEXT: subw a1, a1, a3 +; CHECK-NEXT: andi a0, a0, 1 +; CHECK-NEXT: slli a0, a0, 11 +; CHECK-NEXT: sw a1, 0(a2) +; CHECK-NEXT: ret +BB: + %I = select i1 %0, i32 -1, i32 0 + %I1 = mul i32 %1, 2048 + %I2 = and i32 2048, %I + store i32 %I1, ptr %2 + ret i32 %I2 +} + +define i32 @i(i1 %0, i32 %1, ptr %2) { +; CHECK-LABEL: i: +; CHECK: # %bb.0: # %BB +; CHECK-NEXT: andi a0, a0, 1 +; CHECK-NEXT: slliw a3, a1, 11 +; CHECK-NEXT: slliw a1, a1, 12 +; CHECK-NEXT: subw a1, a1, a3 +; CHECK-NEXT: addi a0, a0, -1 +; CHECK-NEXT: lui a3, 1 +; CHECK-NEXT: addiw a3, a3, -2048 +; CHECK-NEXT: and a0, a0, a3 +; CHECK-NEXT: sw a1, 0(a2) +; CHECK-NEXT: ret +BB: + %I = select i1 %0, i32 0, i32 -1 + %I1 = mul i32 %1, 2048 + %I2 = and i32 2048, %I + store i32 %I1, ptr %2 + ret i32 %I2 +} -- 2.7.4