[LV] Logical and/or select costs

[dmgreen]

Summary

D99674 stopped the folding of certain select operations into and/or, due to incorrect folding in the presence of poison. D97360 added some costs to attempt to account for the change, but only worked at the getUserCost level, not the getCmpSelInstrCost that the vectorizer will use directly. This adds similar logic into the vectorizer to handle these logical and/or selects, treating them like and/or directly.

This fixes 60% performance regressions from code like the attached test case.

[aqjune]

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

7458

If the select is loop invariant, it is still considered expensive - is there a reason why it is so?

[dmgreen]

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

7458

That would become a %a5 = select i1 %c, <4 x i1> <i1 1, i1 1, i1 1, i1 1>, <4 x i1> %a4
Which I don't think would then be converted to an and/or

At least under MVE, it becomes a branch, as that is how we lower vector SELECTs (as opposed to VSELECT, which are lowered to an MVE instruction using the predicate register).
https://godbolt.org/z/ecev1KcKe
Which can end up in the loop:
https://godbolt.org/z/6abW4M5vn

.LBB0_8:
        vmsr    p0, r5
.LBB0_9:
        vldrw.u32       q1, [r4], #16
        adds    r6, #16
        vpsel   q0, q0, q1
        vstrb.8 q0, [r9], #16
        subs.w  lr, lr, #1
        bne     .LBB0_10
        b       .LBB0_12
.LBB0_10:
        vldrw.u32       q0, [r6]
        cmp.w   r12, #0
        ble     .LBB0_8
        vcmp.s32        gt, q0, zr
        b       ,LBB0_9

[aqjune]

LGTM, Thanks!

[dmgreen]

Thanks

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Use.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
return N * TTI.getArithmeticInstrCost(
                    TargetTransformInfo::OK_AnyValue,
                    TargetTransformInfo::OP_None, TargetTransformInfo::OP_None,
                    I->getOperand(0), I);
   }
   case Instruction::Select: {
     SelectInst *SI = cast<SelectInst>(I);
     const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
     bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
+
+    const Value *Op0, *Op1;
+    using namespace llvm::PatternMatch;
+    if (!ScalarCond && (match(I, m_LogicalAnd(m_Value(Op0), m_Value(Op1))) ||
+                        match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1))))) {
+      // select x, y, false --> x & y
+      // select x, true, y --> x | y
+      TTI::OperandValueProperties Op1VP = TTI::OP_None;
+      TTI::OperandValueProperties Op2VP = TTI::OP_None;
+      TTI::OperandValueKind Op1VK = TTI::getOperandInfo(Op0, Op1VP);
+      TTI::OperandValueKind Op2VK = TTI::getOperandInfo(Op1, Op2VP);
+      assert(Op0->getType()->getScalarSizeInBits() == 1 &&
+              Op1->getType()->getScalarSizeInBits() == 1);
+
+      SmallVector<const Value *, 2> Operands{Op0, Op1};
+      return TTI.getArithmeticInstrCost(
+          match(I, m_LogicalOr()) ? Instruction::Or : Instruction::And, VectorTy,
+          CostKind, Op1VK, Op2VK, Op1VP, Op2VP, Operands, I);
+    }
+
     Type *CondTy = SI->getCondition()->getType();
     if (!ScalarCond)
       CondTy = VectorType::get(CondTy, VF);
     return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy,
                                   CmpInst::BAD_ICMP_PREDICATE, CostKind, I);
   }
   case Instruction::ICmp:
   case Instruction::FCmp: {

llvm/test/Transforms/LoopVectorize/ARM/mve-selectandorcost.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -loop-vectorize -instcombine -simplifycfg < %s -S -o - | FileCheck %s --check-prefix=CHECK
 ; RUN: opt -loop-vectorize -debug-only=loop-vectorize -disable-output < %s 2>&1 | FileCheck %s --check-prefix=CHECK-COST
 ; REQUIRES: asserts
 
 target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "thumbv8.1m.main-arm-none-eabi"
 
 ; CHECK-COST-LABEL: test
 ; CHECK-COST: LV: Found an estimated cost of 1 for VF 1 For instruction:   %or.cond = select i1 %cmp2, i1 true, i1 %cmp3
-; CHECK-COST: LV: Found an estimated cost of 20 for VF 2 For instruction:   %or.cond = select i1 %cmp2, i1 true, i1 %cmp3
-; CHECK-COST: LV: Found an estimated cost of 40 for VF 4 For instruction:   %or.cond = select i1 %cmp2, i1 true, i1 %cmp3
+; CHECK-COST: LV: Found an estimated cost of 2 for VF 2 For instruction:   %or.cond = select i1 %cmp2, i1 true, i1 %cmp3
+; CHECK-COST: LV: Found an estimated cost of 2 for VF 4 For instruction:   %or.cond = select i1 %cmp2, i1 true, i1 %cmp3
 
 define float @test(float* nocapture readonly %pA, float* nocapture readonly %pB, i32 %blockSize) #0 {
 ; CHECK-LABEL: @test(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP_NOT16:%.*]] = icmp eq i32 [[BLOCKSIZE:%.*]], 0
-; CHECK-NEXT:    br i1 [[CMP_NOT16]], label [[WHILE_END:%.*]], label [[WHILE_BODY:%.*]]
+; CHECK-NEXT:    br i1 [[CMP_NOT16]], label [[WHILE_END:%.*]], label [[WHILE_BODY_PREHEADER:%.*]]
+; CHECK:       while.body.preheader:
+; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i32 [[BLOCKSIZE]], 4
+; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK:       vector.ph:
+; CHECK-NEXT:    [[N_VEC:%.*]] = and i32 [[BLOCKSIZE]], -4
+; CHECK-NEXT:    [[IND_END:%.*]] = getelementptr float, float* [[PA:%.*]], i32 [[N_VEC]]
+; CHECK-NEXT:    [[IND_END2:%.*]] = getelementptr float, float* [[PB:%.*]], i32 [[N_VEC]]
+; CHECK-NEXT:    [[IND_END4:%.*]] = and i32 [[BLOCKSIZE]], 3
+; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
+; CHECK:       vector.body:
+; CHECK-NEXT:    [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <4 x float> [ zeroinitializer, [[VECTOR_PH]] ], [ [[PREDPHI:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[NEXT_GEP:%.*]] = getelementptr float, float* [[PA]], i32 [[INDEX]]
+; CHECK-NEXT:    [[NEXT_GEP5:%.*]] = getelementptr float, float* [[PB]], i32 [[INDEX]]
+; CHECK-NEXT:    [[TMP0:%.*]] = bitcast float* [[NEXT_GEP]] to <4 x float>*
+; CHECK-NEXT:    [[WIDE_LOAD:%.*]] = load <4 x float>, <4 x float>* [[TMP0]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast float* [[NEXT_GEP5]] to <4 x float>*
+; CHECK-NEXT:    [[WIDE_LOAD6:%.*]] = load <4 x float>, <4 x float>* [[TMP1]], align 4
+; CHECK-NEXT:    [[TMP2:%.*]] = fcmp fast oeq <4 x float> [[WIDE_LOAD]], zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = fcmp fast oeq <4 x float> [[WIDE_LOAD6]], zeroinitializer
+; CHECK-NEXT:    [[TMP4:%.*]] = select <4 x i1> [[TMP2]], <4 x i1> [[TMP3]], <4 x i1> zeroinitializer
+; CHECK-NEXT:    [[TMP5:%.*]] = call fast <4 x float> @llvm.fabs.v4f32(<4 x float> [[WIDE_LOAD]])
+; CHECK-NEXT:    [[TMP6:%.*]] = call fast <4 x float> @llvm.fabs.v4f32(<4 x float> [[WIDE_LOAD6]])
+; CHECK-NEXT:    [[TMP7:%.*]] = fadd fast <4 x float> [[TMP6]], [[TMP5]]
+; CHECK-NEXT:    [[TMP8:%.*]] = fsub fast <4 x float> [[WIDE_LOAD]], [[WIDE_LOAD6]]
+; CHECK-NEXT:    [[TMP9:%.*]] = call fast <4 x float> @llvm.fabs.v4f32(<4 x float> [[TMP8]])
+; CHECK-NEXT:    [[TMP10:%.*]] = fdiv fast <4 x float> [[TMP9]], [[TMP7]]
+; CHECK-NEXT:    [[TMP11:%.*]] = fadd fast <4 x float> [[TMP10]], [[VEC_PHI]]
+; CHECK-NEXT:    [[PREDPHI]] = select <4 x i1> [[TMP4]], <4 x float> [[VEC_PHI]], <4 x float> [[TMP11]]
+; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 4
+; CHECK-NEXT:    [[TMP12:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT:    br i1 [[TMP12]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK:       middle.block:
+; CHECK-NEXT:    [[TMP13:%.*]] = call fast float @llvm.vector.reduce.fadd.v4f32(float -0.000000e+00, <4 x float> [[PREDPHI]])
+; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i32 [[N_VEC]], [[BLOCKSIZE]]
+; CHECK-NEXT:    br i1 [[CMP_N]], label [[WHILE_END]], label [[SCALAR_PH]]
+; CHECK:       scalar.ph:
+; CHECK-NEXT:    [[BC_RESUME_VAL:%.*]] = phi float* [ [[IND_END]], [[MIDDLE_BLOCK]] ], [ [[PA]], [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[BC_RESUME_VAL1:%.*]] = phi float* [ [[IND_END2]], [[MIDDLE_BLOCK]] ], [ [[PB]], [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[BC_RESUME_VAL3:%.*]] = phi i32 [ [[IND_END4]], [[MIDDLE_BLOCK]] ], [ [[BLOCKSIZE]], [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[BC_MERGE_RDX:%.*]] = phi float [ [[TMP13]], [[MIDDLE_BLOCK]] ], [ 0.000000e+00, [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    br label [[WHILE_BODY:%.*]]
 ; CHECK:       while.body:
-; CHECK-NEXT:    [[PA_ADDR_020:%.*]] = phi float* [ [[INCDEC_PTR:%.*]], [[IF_END:%.*]] ], [ [[PA:%.*]], [[ENTRY:%.*]] ]
-; CHECK-NEXT:    [[PB_ADDR_019:%.*]] = phi float* [ [[INCDEC_PTR1:%.*]], [[IF_END]] ], [ [[PB:%.*]], [[ENTRY]] ]
-; CHECK-NEXT:    [[BLOCKSIZE_ADDR_018:%.*]] = phi i32 [ [[DEC:%.*]], [[IF_END]] ], [ [[BLOCKSIZE]], [[ENTRY]] ]
-; CHECK-NEXT:    [[ACCUM_017:%.*]] = phi float [ [[ACCUM_1:%.*]], [[IF_END]] ], [ 0.000000e+00, [[ENTRY]] ]
+; CHECK-NEXT:    [[PA_ADDR_020:%.*]] = phi float* [ [[INCDEC_PTR:%.*]], [[IF_END:%.*]] ], [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ]
+; CHECK-NEXT:    [[PB_ADDR_019:%.*]] = phi float* [ [[INCDEC_PTR1:%.*]], [[IF_END]] ], [ [[BC_RESUME_VAL1]], [[SCALAR_PH]] ]
+; CHECK-NEXT:    [[BLOCKSIZE_ADDR_018:%.*]] = phi i32 [ [[DEC:%.*]], [[IF_END]] ], [ [[BC_RESUME_VAL3]], [[SCALAR_PH]] ]
+; CHECK-NEXT:    [[ACCUM_017:%.*]] = phi float [ [[ACCUM_1:%.*]], [[IF_END]] ], [ [[BC_MERGE_RDX]], [[SCALAR_PH]] ]
 ; CHECK-NEXT:    [[INCDEC_PTR]] = getelementptr inbounds float, float* [[PA_ADDR_020]], i32 1
-; CHECK-NEXT:    [[TMP0:%.*]] = load float, float* [[PA_ADDR_020]], align 4
+; CHECK-NEXT:    [[TMP14:%.*]] = load float, float* [[PA_ADDR_020]], align 4
 ; CHECK-NEXT:    [[INCDEC_PTR1]] = getelementptr inbounds float, float* [[PB_ADDR_019]], i32 1
-; CHECK-NEXT:    [[TMP1:%.*]] = load float, float* [[PB_ADDR_019]], align 4
-; CHECK-NEXT:    [[CMP2:%.*]] = fcmp fast une float [[TMP0]], 0.000000e+00
-; CHECK-NEXT:    [[CMP3:%.*]] = fcmp fast une float [[TMP1]], 0.000000e+00
+; CHECK-NEXT:    [[TMP15:%.*]] = load float, float* [[PB_ADDR_019]], align 4
+; CHECK-NEXT:    [[CMP2:%.*]] = fcmp fast une float [[TMP14]], 0.000000e+00
+; CHECK-NEXT:    [[CMP3:%.*]] = fcmp fast une float [[TMP15]], 0.000000e+00
 ; CHECK-NEXT:    [[OR_COND:%.*]] = select i1 [[CMP2]], i1 true, i1 [[CMP3]]
 ; CHECK-NEXT:    br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[IF_END]]
 ; CHECK:       if.then:
-; CHECK-NEXT:    [[TMP2:%.*]] = tail call fast float @llvm.fabs.f32(float [[TMP0]])
-; CHECK-NEXT:    [[TMP3:%.*]] = tail call fast float @llvm.fabs.f32(float [[TMP1]])
-; CHECK-NEXT:    [[ADD:%.*]] = fadd fast float [[TMP3]], [[TMP2]]
-; CHECK-NEXT:    [[SUB:%.*]] = fsub fast float [[TMP0]], [[TMP1]]
-; CHECK-NEXT:    [[TMP4:%.*]] = tail call fast float @llvm.fabs.f32(float [[SUB]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv fast float [[TMP4]], [[ADD]]
+; CHECK-NEXT:    [[TMP16:%.*]] = tail call fast float @llvm.fabs.f32(float [[TMP14]])
+; CHECK-NEXT:    [[TMP17:%.*]] = tail call fast float @llvm.fabs.f32(float [[TMP15]])
+; CHECK-NEXT:    [[ADD:%.*]] = fadd fast float [[TMP17]], [[TMP16]]
+; CHECK-NEXT:    [[SUB:%.*]] = fsub fast float [[TMP14]], [[TMP15]]
+; CHECK-NEXT:    [[TMP18:%.*]] = tail call fast float @llvm.fabs.f32(float [[SUB]])
+; CHECK-NEXT:    [[DIV:%.*]] = fdiv fast float [[TMP18]], [[ADD]]
 ; CHECK-NEXT:    [[ADD4:%.*]] = fadd fast float [[DIV]], [[ACCUM_017]]
 ; CHECK-NEXT:    br label [[IF_END]]
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[ACCUM_1]] = phi float [ [[ADD4]], [[IF_THEN]] ], [ [[ACCUM_017]], [[WHILE_BODY]] ]
 ; CHECK-NEXT:    [[DEC]] = add i32 [[BLOCKSIZE_ADDR_018]], -1
 ; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[DEC]], 0
-; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[WHILE_END]], label [[WHILE_BODY]]
+; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[WHILE_END]], label [[WHILE_BODY]], !llvm.loop [[LOOP2:![0-9]+]]
 ; CHECK:       while.end:
-; CHECK-NEXT:    [[ACCUM_0_LCSSA:%.*]] = phi float [ 0.000000e+00, [[ENTRY]] ], [ [[ACCUM_1]], [[IF_END]] ]
+; CHECK-NEXT:    [[ACCUM_0_LCSSA:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[ACCUM_1]], [[IF_END]] ], [ [[TMP13]], [[MIDDLE_BLOCK]] ]
 ; CHECK-NEXT:    ret float [[ACCUM_0_LCSSA]]
 ;
 entry:
   %cmp.not16 = icmp eq i32 %blockSize, 0
   br i1 %cmp.not16, label %while.end, label %while.body
 
 while.body:                                       ; preds = %entry, %if.end
   %pA.addr.020 = phi float* [ %incdec.ptr, %if.end ], [ %pA, %entry ]