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[VPlan] Support VPWidenSelectRecipe in narrowToSingleScalar.

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VPWidenSelectRecipes are single scalars if all their operands are. Add
support for narrowing them to a single scalar VPReplicateRecipe.

This fixes a crash after
https://github.com/llvm/llvm-project/pull/142433 (aa24029319) when
due to a replicate recipe not being converted to single-scalar being
hoisted to the vector preheader.
This commit is contained in:
Florian Hahn
2025-06-27 15:42:41 +01:00
parent 1df3e0a275
commit 3b7b95f78e
3 changed files with 72 additions and 1 deletions
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2
llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
View File

@@ -1221,7 +1221,7 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) {
auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
if (!RepR && !isa<VPWidenRecipe>(&R))
if (!RepR && !isa<VPWidenRecipe, VPWidenSelectRecipe>(&R))
continue;
if (RepR && (RepR->isSingleScalar() || RepR->isPredicated()))
continue;

2
llvm/lib/Transforms/Vectorize/VPlanUtils.h
View File

@@ -75,6 +75,8 @@ inline bool isSingleScalar(const VPValue *VPV) {
return PreservesUniformity(WidenR->getOpcode()) &&
all_of(WidenR->operands(), isSingleScalar);
}
if (auto *WidenR = dyn_cast<VPWidenSelectRecipe>(VPV))
return all_of(WidenR->operands(), isSingleScalar);
if (auto *VPI = dyn_cast<VPInstruction>(VPV))
return VPI->isSingleScalar() || VPI->isVectorToScalar() ||
(PreservesUniformity(VPI->getOpcode()) &&

69
llvm/test/Transforms/LoopVectorize/narrow-to-single-scalar.ll Normal file
View File

@@ -0,0 +1,69 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -p loop-vectorize -force-vector-width=4 -S %s | FileCheck %s
define void @narrow_select_to_single_scalar(i1 %invar.cond, ptr noalias %A, ptr noalias %B, ptr noalias %C) {
; CHECK-LABEL: define void @narrow_select_to_single_scalar(
; CHECK-SAME: i1 [[INVAR_COND:%.*]], ptr noalias [[A:%.*]], ptr noalias [[B:%.*]], ptr noalias [[C:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_PH:.*]]
; CHECK: [[VECTOR_PH]]:
; CHECK-NEXT: [[TMP0:%.*]] = select i1 [[INVAR_COND]], i16 0, i16 1
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i16, ptr [[C]], i16 [[TMP0]]
; CHECK-NEXT: br label %[[VECTOR_BODY:.*]]
; CHECK: [[VECTOR_BODY]]:
; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
; CHECK-NEXT: [[OFFSET_IDX:%.*]] = trunc i32 [[INDEX]] to i16
; CHECK-NEXT: [[TMP2:%.*]] = add i16 [[OFFSET_IDX]], 0
; CHECK-NEXT: [[TMP3:%.*]] = add i16 [[OFFSET_IDX]], 1
; CHECK-NEXT: [[TMP4:%.*]] = add i16 [[OFFSET_IDX]], 2
; CHECK-NEXT: [[TMP5:%.*]] = add i16 [[OFFSET_IDX]], 3
; CHECK-NEXT: [[TMP6:%.*]] = getelementptr i8, ptr [[A]], i16 [[TMP5]]
; CHECK-NEXT: [[TMP7:%.*]] = load i16, ptr [[TMP6]], align 1
; CHECK-NEXT: store i16 [[TMP7]], ptr [[B]], align 1
; CHECK-NEXT: store i16 0, ptr [[TMP1]], align 1
; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 4
; CHECK-NEXT: [[TMP8:%.*]] = icmp eq i32 [[INDEX_NEXT]], 1024
; CHECK-NEXT: br i1 [[TMP8]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK: [[MIDDLE_BLOCK]]:
; CHECK-NEXT: br i1 false, label %[[EXIT:.*]], label %[[SCALAR_PH]]
; CHECK: [[SCALAR_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i16 [ 1024, %[[MIDDLE_BLOCK]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: br label %[[LOOP_HEADER:.*]]
; CHECK: [[LOOP_HEADER]]:
; CHECK-NEXT: [[IV:%.*]] = phi i16 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[IV_NEXT:%.*]], %[[LOOP_HEADER]] ]
; CHECK-NEXT: [[GEP_A:%.*]] = getelementptr i8, ptr [[A]], i16 [[IV]]
; CHECK-NEXT: [[L_0:%.*]] = load i16, ptr [[GEP_A]], align 1
; CHECK-NEXT: store i16 [[L_0]], ptr [[B]], align 1
; CHECK-NEXT: [[INVAR_SEL:%.*]] = select i1 [[INVAR_COND]], i16 0, i16 1
; CHECK-NEXT: [[GEP_C:%.*]] = getelementptr i16, ptr [[C]], i16 [[INVAR_SEL]]
; CHECK-NEXT: store i16 0, ptr [[GEP_C]], align 1
; CHECK-NEXT: [[IV_NEXT]] = add i16 [[IV]], 1
; CHECK-NEXT: [[EC:%.*]] = icmp ne i16 [[IV]], 1024
; CHECK-NEXT: br i1 [[EC]], label %[[LOOP_HEADER]], label %[[EXIT]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: ret void
;
entry:
br label %loop.header
loop.header:
%iv = phi i16 [ 0, %entry ], [ %iv.next, %loop.header ]
%gep.A = getelementptr i8, ptr %A, i16 %iv
%l.0 = load i16, ptr %gep.A, align 1
store i16 %l.0, ptr %B, align 1
%invar.sel = select i1 %invar.cond, i16 0, i16 1
%gep.C = getelementptr i16, ptr %C, i16 %invar.sel
store i16 0, ptr %gep.C, align 1
%iv.next = add i16 %iv, 1
%ec = icmp ne i16 %iv, 1024
br i1 %ec, label %loop.header, label %exit
exit:
ret void
}
;.
; 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]]}
;.