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[LV] Account for any-of reduction when computing costs of blend phis.
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Any-of reductions are narrowed to i1. Update the legacy cost model to
use the correct type when computing the cost of a phi that gets lowered
to selects (BLEND).

This fixes a divergence between legacy and VPlan-based cost models after
36fc291.

Fixes llvm#111874.
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@fhahn
fhahn committed Oct 11, 2024
1 parent 6a65e98 commit 65da32c
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24 changes: 22 additions & 2 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6480,12 +6480,32 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I,
// Phi nodes in non-header blocks (not inductions, reductions, etc.) are
// converted into select instructions. We require N - 1 selects per phi
// node, where N is the number of incoming values.
if (VF.isVector() && Phi->getParent() != TheLoop->getHeader())
if (VF.isVector() && Phi->getParent() != TheLoop->getHeader()) {
Type *ResultTy = Phi->getType();

// All instructions in an Any-of reduction chain are narrowed to bool.
// Check if that is the case for this phi node.
auto *HeaderUser = cast_if_present<PHINode>(
find_singleton<User>(Phi->users(), [this](User *U, bool) -> User * {
auto *Phi = dyn_cast<PHINode>(U);
if (Phi && Phi->getParent() == TheLoop->getHeader())
return Phi;
return nullptr;
}));
if (HeaderUser) {
auto &ReductionVars = Legal->getReductionVars();
auto Iter = ReductionVars.find(HeaderUser);
if (Iter != ReductionVars.end() &&
RecurrenceDescriptor::isAnyOfRecurrenceKind(
Iter->second.getRecurrenceKind()))
ResultTy = Type::getInt1Ty(Phi->getContext());
}
return (Phi->getNumIncomingValues() - 1) *
TTI.getCmpSelInstrCost(
Instruction::Select, ToVectorTy(Phi->getType(), VF),
Instruction::Select, ToVectorTy(ResultTy, VF),
ToVectorTy(Type::getInt1Ty(Phi->getContext()), VF),
CmpInst::BAD_ICMP_PREDICATE, CostKind);
}

return TTI.getCFInstrCost(Instruction::PHI, CostKind);
}
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167 changes: 167 additions & 0 deletions llvm/test/Transforms/LoopVectorize/RISCV/blend-any-of-reduction-cost.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,167 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -p loop-vectorize -S %s | FileCheck %s

target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128"
target triple = "riscv64-unknown-linux-gnu"

; Test case for https://github.com/llvm/llvm-project/issues/111874.
define i32 @any_of_reduction_used_in_blend(ptr %src, i64 %N, i1 %c.0, i1 %c.1) #0 {
; CHECK-LABEL: define i32 @any_of_reduction_used_in_blend(
; CHECK-SAME: ptr [[SRC:%.*]], i64 [[N:%.*]], i1 [[C_0:%.*]], i1 [[C_1:%.*]]) #[[ATTR0:[0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
; CHECK-NEXT: [[ANY_OF_RED:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[ANY_OF_RED_NEXT:%.*]], %[[LOOP_LATCH:.*]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[IV_NEXT:%.*]], %[[LOOP_LATCH]] ]
; CHECK-NEXT: br i1 [[C_0]], label %[[LOOP_LATCH]], label %[[ELSE_1:.*]]
; CHECK: [[ELSE_1]]:
; CHECK-NEXT: br i1 [[C_1]], label %[[LOOP_LATCH]], label %[[ELSE_2:.*]]
; CHECK: [[ELSE_2]]:
; CHECK-NEXT: [[L:%.*]] = load ptr, ptr [[SRC]], align 8
; CHECK-NEXT: [[C_2:%.*]] = icmp eq ptr [[L]], null
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_2]], i32 0, i32 [[ANY_OF_RED]]
; CHECK-NEXT: br label %[[LOOP_LATCH]]
; CHECK: [[LOOP_LATCH]]:
; CHECK-NEXT: [[ANY_OF_RED_NEXT]] = phi i32 [ [[ANY_OF_RED]], %[[LOOP_HEADER]] ], [ [[ANY_OF_RED]], %[[ELSE_1]] ], [ [[SEL]], %[[ELSE_2]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp eq i64 [[IV_NEXT]], [[N]]
; CHECK-NEXT: br i1 [[EC]], label %[[EXIT:.*]], label %[[LOOP_HEADER]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[RES:%.*]] = phi i32 [ [[ANY_OF_RED_NEXT]], %[[LOOP_LATCH]] ]
; CHECK-NEXT: ret i32 [[RES]]
;
entry:
br label %loop.header

loop.header:
%any.of.red = phi i32 [ 0, %entry ], [ %any.of.red.next, %loop.latch ]
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop.latch ]
br i1 %c.0, label %loop.latch, label %else.1

else.1:
br i1 %c.1, label %loop.latch, label %else.2

else.2:
%l = load ptr, ptr %src, align 8
%c.2 = icmp eq ptr %l, null
%sel = select i1 %c.2, i32 0, i32 %any.of.red
br label %loop.latch

loop.latch:
%any.of.red.next = phi i32 [ %any.of.red, %loop.header ], [ %any.of.red, %else.1 ], [ %sel, %else.2 ]
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, %N
br i1 %ec, label %exit, label %loop.header

exit:
%res = phi i32 [ %any.of.red.next, %loop.latch ]
ret i32 %res
}

define i32 @any_of_reduction_used_in_blend_with_mutliple_phis(ptr %src, i64 %N, i1 %c.0, i1 %c.1) #0 {
; CHECK-LABEL: define i32 @any_of_reduction_used_in_blend_with_mutliple_phis(
; CHECK-SAME: ptr [[SRC:%.*]], i64 [[N:%.*]], i1 [[C_0:%.*]], i1 [[C_1:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[TMP0:%.*]] = call i64 @llvm.vscale.i64()
; CHECK-NEXT: [[TMP1:%.*]] = mul i64 [[TMP0]], 2
; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[N]], [[TMP1]]
; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[TMP2:%.*]] = call i64 @llvm.vscale.i64()
; CHECK-NEXT: [[TMP3:%.*]] = mul i64 [[TMP2]], 2
; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[N]], [[TMP3]]
; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[N]], [[N_MOD_VF]]
; CHECK-NEXT: [[TMP4:%.*]] = call i64 @llvm.vscale.i64()
; CHECK-NEXT: [[TMP5:%.*]] = mul i64 [[TMP4]], 2
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 2 x i1> poison, i1 [[C_0]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 2 x i1> [[BROADCAST_SPLATINSERT]], <vscale x 2 x i1> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <vscale x 2 x i1> poison, i1 [[C_1]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT2:%.*]] = shufflevector <vscale x 2 x i1> [[BROADCAST_SPLATINSERT1]], <vscale x 2 x i1> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: [[BROADCAST_SPLATINSERT3:%.*]] = insertelement <vscale x 2 x ptr> poison, ptr [[SRC]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT4:%.*]] = shufflevector <vscale x 2 x ptr> [[BROADCAST_SPLATINSERT3]], <vscale x 2 x ptr> poison, <vscale x 2 x i32> zeroinitializer
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[VEC_PHI:%.*]] = phi <vscale x 2 x i1> [ zeroinitializer, %[[VECTOR_PH]] ], [ [[PREDPHI:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[TMP6:%.*]] = xor <vscale x 2 x i1> [[BROADCAST_SPLAT]], shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> poison, i1 true, i64 0), <vscale x 2 x i1> poison, <vscale x 2 x i32> zeroinitializer)
; CHECK-NEXT: [[TMP7:%.*]] = xor <vscale x 2 x i1> [[BROADCAST_SPLAT2]], shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> poison, i1 true, i64 0), <vscale x 2 x i1> poison, <vscale x 2 x i32> zeroinitializer)
; CHECK-NEXT: [[TMP8:%.*]] = select <vscale x 2 x i1> [[TMP6]], <vscale x 2 x i1> [[TMP7]], <vscale x 2 x i1> zeroinitializer
; CHECK-NEXT: [[WIDE_MASKED_GATHER:%.*]] = call <vscale x 2 x ptr> @llvm.masked.gather.nxv2p0.nxv2p0(<vscale x 2 x ptr> [[BROADCAST_SPLAT4]], i32 8, <vscale x 2 x i1> [[TMP8]], <vscale x 2 x ptr> poison)
; CHECK-NEXT: [[TMP9:%.*]] = icmp eq <vscale x 2 x ptr> [[WIDE_MASKED_GATHER]], zeroinitializer
; CHECK-NEXT: [[TMP10:%.*]] = or <vscale x 2 x i1> [[VEC_PHI]], [[TMP9]]
; CHECK-NEXT: [[PREDPHI]] = select <vscale x 2 x i1> [[TMP8]], <vscale x 2 x i1> [[TMP10]], <vscale x 2 x i1> [[VEC_PHI]]
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], [[TMP5]]
; CHECK-NEXT: [[TMP11:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
; CHECK-NEXT: br i1 [[TMP11]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: [[MIDDLE_BLOCK]]:
; CHECK-NEXT: [[TMP12:%.*]] = call i1 @llvm.vector.reduce.or.nxv2i1(<vscale x 2 x i1> [[PREDPHI]])
; CHECK-NEXT: [[TMP13:%.*]] = freeze i1 [[TMP12]]
; CHECK-NEXT: [[RDX_SELECT:%.*]] = select i1 [[TMP13]], i32 0, i32 0
; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[N]], [[N_VEC]]
; CHECK-NEXT: br i1 [[CMP_N]], label %[[EXIT:.*]], label %[[SCALAR_PH]]
; CHECK: [[SCALAR_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[N_VEC]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: [[BC_MERGE_RDX:%.*]] = phi i32 [ [[RDX_SELECT]], %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
; CHECK-NEXT: [[ANY_OF_RED:%.*]] = phi i32 [ [[BC_MERGE_RDX]], %[[SCALAR_PH]] ], [ [[ANY_OF_RED_NEXT:%.*]], %[[LOOP_LATCH:.*]] ]
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], %[[LOOP_LATCH]] ]
; CHECK-NEXT: br i1 [[C_0]], label %[[X_1:.*]], label %[[ELSE_1:.*]]
; CHECK: [[ELSE_1]]:
; CHECK-NEXT: br i1 [[C_1]], label %[[X_1]], label %[[ELSE_2:.*]]
; CHECK: [[ELSE_2]]:
; CHECK-NEXT: [[L:%.*]] = load ptr, ptr [[SRC]], align 8
; CHECK-NEXT: [[C_2:%.*]] = icmp eq ptr [[L]], null
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[C_2]], i32 0, i32 [[ANY_OF_RED]]
; CHECK-NEXT: br label %[[LOOP_LATCH]]
; CHECK: [[X_1]]:
; CHECK-NEXT: [[P:%.*]] = phi i32 [ [[ANY_OF_RED]], %[[LOOP_HEADER]] ], [ [[ANY_OF_RED]], %[[ELSE_1]] ]
; CHECK-NEXT: br label %[[LOOP_LATCH]]
; CHECK: [[LOOP_LATCH]]:
; CHECK-NEXT: [[ANY_OF_RED_NEXT]] = phi i32 [ [[P]], %[[X_1]] ], [ [[SEL]], %[[ELSE_2]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp eq i64 [[IV_NEXT]], [[N]]
; CHECK-NEXT: br i1 [[EC]], label %[[EXIT]], label %[[LOOP_HEADER]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: [[RES:%.*]] = phi i32 [ [[ANY_OF_RED_NEXT]], %[[LOOP_LATCH]] ], [ [[RDX_SELECT]], %[[MIDDLE_BLOCK]] ]
; CHECK-NEXT: ret i32 [[RES]]
;
entry:
br label %loop.header

loop.header:
%any.of.red = phi i32 [ 0, %entry ], [ %any.of.red.next, %loop.latch ]
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop.latch ]
br i1 %c.0, label %x.1, label %else.1

else.1:
br i1 %c.1, label %x.1, label %else.2

else.2:
%l = load ptr, ptr %src, align 8
%c.2 = icmp eq ptr %l, null
%sel = select i1 %c.2, i32 0, i32 %any.of.red
br label %loop.latch

x.1:
%p = phi i32 [ %any.of.red, %loop.header ], [ %any.of.red, %else.1 ]
br label %loop.latch

loop.latch:
%any.of.red.next = phi i32 [ %p, %x.1 ], [ %sel, %else.2 ]
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, %N
br i1 %ec, label %exit, label %loop.header

exit:
%res = phi i32 [ %any.of.red.next, %loop.latch ]
ret i32 %res
}

attributes #0 = { "target-cpu"="sifive-p670" }
;.
; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]], [[META2:![0-9]+]]}
; CHECK: [[META1]] = !{!"llvm.loop.isvectorized", i32 1}
; CHECK: [[META2]] = !{!"llvm.loop.unroll.runtime.disable"}
; CHECK: [[LOOP3]] = distinct !{[[LOOP3]], [[META2]], [[META1]]}
;.

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