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Revert "[VPlan] Remove legacy costing inside VPBlendRecipe::computeCost (#171846)"

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This reverts commit fd5f53aa9b.

It's triggering legacy cost model assertions reported in
https://github.com/llvm/llvm-project/pull/171846#issuecomment-3647640019
This commit is contained in:
Luke Lau
2025-12-13 20:05:34 +08:00
parent 95e4dc62b1
commit 4ea8157773
3 changed files with 46 additions and 18 deletions
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5
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@@ -7081,11 +7081,6 @@ static bool planContainsAdditionalSimplifications(VPlan &Plan,
return true;
}
// The legacy cost model costs non-header phis with a scalar VF as a phi,
// but scalar unrolled VPlans will have VPBlendRecipes which emit selects.
if (VF.isScalar() && isa<VPBlendRecipe>(&R))
return true;
/// If a VPlan transform folded a recipe to one producing a single-scalar,
/// but the original instruction wasn't uniform-after-vectorization in the
/// legacy cost model, the legacy cost overestimates the actual cost.

5
llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
View File

@@ -2551,6 +2551,11 @@ void VPVectorPointerRecipe::printRecipe(raw_ostream &O, const Twine &Indent,
InstructionCost VPBlendRecipe::computeCost(ElementCount VF,
VPCostContext &Ctx) const {
// Handle cases where only the first lane is used the same way as the legacy
// cost model.
if (vputils::onlyFirstLaneUsed(this))
return Ctx.TTI.getCFInstrCost(Instruction::PHI, Ctx.CostKind);
Type *ResultTy = toVectorTy(Ctx.Types.inferScalarType(this), VF);
Type *CmpTy = toVectorTy(Type::getInt1Ty(Ctx.Types.getContext()), VF);
return (getNumIncomingValues() - 1) *

54
llvm/test/Transforms/LoopVectorize/X86/replicate-uniform-call.ll
View File

@@ -8,25 +8,48 @@ target triple = "x86_64-unknown-linux-gnu"
define void @smax_call_uniform(ptr %dst, i64 %x) {
; CHECK-LABEL: define void @smax_call_uniform(
; CHECK-SAME: ptr [[DST:%.*]], i64 [[X:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[C:%.*]] = icmp ult i8 -68, -69
; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i64 [[X]], 0
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[INDEX_NEXT:%.*]], %[[LOOP_LATCH:.*]] ]
; CHECK-NEXT: br i1 [[C]], label %[[LOOP_LATCH]], label %[[ELSE:.*]]
; CHECK: [[ELSE]]:
; CHECK-NEXT: [[REM:%.*]] = urem i64 [[MUL]], [[X]]
; CHECK-NEXT: [[SMAX:%.*]] = tail call i64 @llvm.smax.i64(i64 [[REM]], i64 0)
; CHECK-NEXT: br label %[[LOOP_LATCH]]
; CHECK: [[LOOP_LATCH]]:
; CHECK-NEXT: [[PREDPHI7:%.*]] = phi i64 [ 1, %[[LOOP_HEADER]] ], [ [[SMAX]], %[[ELSE]] ]
; CHECK-NEXT: br label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i1> poison, i1 [[C]], i64 0
; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i1> [[BROADCAST_SPLATINSERT]], <2 x i1> poison, <2 x i32> zeroinitializer
; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i1> [[BROADCAST_SPLAT]], splat (i1 true)
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[PRED_UREM_CONTINUE6:.*]] ]
; CHECK-NEXT: [[TMP2:%.*]] = extractelement <2 x i1> [[TMP1]], i32 0
; CHECK-NEXT: br i1 [[TMP2]], label %[[PRED_UREM_IF:.*]], label %[[PRED_UREM_CONTINUE:.*]]
; CHECK: [[PRED_UREM_IF]]:
; CHECK-NEXT: br label %[[PRED_UREM_CONTINUE]]
; CHECK: [[PRED_UREM_CONTINUE]]:
; CHECK-NEXT: [[TMP5:%.*]] = extractelement <2 x i1> [[TMP1]], i32 1
; CHECK-NEXT: br i1 [[TMP5]], label %[[PRED_UREM_IF1:.*]], label %[[PRED_UREM_CONTINUE2:.*]]
; CHECK: [[PRED_UREM_IF1]]:
; CHECK-NEXT: br label %[[PRED_UREM_CONTINUE2]]
; CHECK: [[PRED_UREM_CONTINUE2]]:
; CHECK-NEXT: [[TMP7:%.*]] = extractelement <2 x i1> [[TMP1]], i32 0
; CHECK-NEXT: br i1 [[TMP7]], label %[[PRED_UREM_IF3:.*]], label %[[PRED_UREM_CONTINUE4:.*]]
; CHECK: [[PRED_UREM_IF3]]:
; CHECK-NEXT: br label %[[PRED_UREM_CONTINUE4]]
; CHECK: [[PRED_UREM_CONTINUE4]]:
; CHECK-NEXT: [[TMP10:%.*]] = extractelement <2 x i1> [[TMP1]], i32 1
; CHECK-NEXT: br i1 [[TMP10]], label %[[PRED_UREM_IF5:.*]], label %[[PRED_UREM_CONTINUE6]]
; CHECK: [[PRED_UREM_IF5]]:
; CHECK-NEXT: br label %[[PRED_UREM_CONTINUE6]]
; CHECK: [[PRED_UREM_CONTINUE6]]:
; CHECK-NEXT: [[TMP13:%.*]] = tail call i64 @llvm.smax.i64(i64 0, i64 0)
; CHECK-NEXT: [[PREDPHI7:%.*]] = select i1 [[C]], i64 1, i64 [[TMP13]]
; CHECK-NEXT: [[TMP17:%.*]] = add i64 [[PREDPHI7]], 1
; CHECK-NEXT: [[TMP19:%.*]] = getelementptr i64, ptr [[DST]], i64 [[TMP17]]
; CHECK-NEXT: store i64 0, ptr [[TMP19]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: store i64 0, ptr [[TMP19]], align 8
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
; CHECK-NEXT: [[TMP20:%.*]] = icmp eq i64 [[INDEX_NEXT]], 1024
; CHECK-NEXT: br i1 [[TMP20]], label %[[EXIT:.*]], label %[[LOOP_HEADER]]
; CHECK-NEXT: br i1 [[TMP20]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: [[MIDDLE_BLOCK]]:
; CHECK-NEXT: br label %[[EXIT:.*]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: ret void
;
@@ -58,3 +81,8 @@ exit:
}
declare i64 @llvm.smax.i64(i64, i64)
;.
; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]], [[META2:![0-9]+]]}
; CHECK: [[META1]] = !{!"llvm.loop.isvectorized", i32 1}
; CHECK: [[META2]] = !{!"llvm.loop.unroll.runtime.disable"}
;.