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[SLU][profcheck] Use the original branch weigths in buildPartialInvariantUnswitchConditionalBranch #164270

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Nov 3, 2025
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[SLU][profcheck] Use the original branch weigths in buildPartialInvariantUnswitchConditionalBranch #164270

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[SLU][profcheck] Use the original branch weigths in `buildPartialInva…
mtrofin Oct 19, 2025
7f94d4a
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mtrofin Oct 31, 2025
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19 changes: 15 additions & 4 deletions llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -337,7 +337,7 @@ static void buildPartialUnswitchConditionalBranch(
static void buildPartialInvariantUnswitchConditionalBranch(
BasicBlock &BB, ArrayRef<Value *> ToDuplicate, bool Direction,
BasicBlock &UnswitchedSucc, BasicBlock &NormalSucc, Loop &L,
MemorySSAUpdater *MSSAU) {
MemorySSAUpdater *MSSAU, const BranchInst &OriginalBranch) {
ValueToValueMapTy VMap;
for (auto *Val : reverse(ToDuplicate)) {
Instruction *Inst = cast<Instruction>(Val);
Expand Down Expand Up @@ -377,8 +377,19 @@ static void buildPartialInvariantUnswitchConditionalBranch(
IRBuilder<> IRB(&BB);
IRB.SetCurrentDebugLocation(DebugLoc::getCompilerGenerated());
Value *Cond = VMap[ToDuplicate[0]];
IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc,
Direction ? &NormalSucc : &UnswitchedSucc);
// The expectation is that ToDuplicate[0] is the condition used by the
// OriginalBranch, case in which we can clone the profile metadata from there.
auto *ProfData =
!ProfcheckDisableMetadataFixes &&
ToDuplicate[0] == skipTrivialSelect(OriginalBranch.getCondition())
? OriginalBranch.getMetadata(LLVMContext::MD_prof)
: nullptr;
auto *BR =
IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc,
Direction ? &NormalSucc : &UnswitchedSucc, ProfData);
if (!ProfData)
setExplicitlyUnknownBranchWeightsIfProfiled(*BR, *BR->getFunction(),
DEBUG_TYPE);
}

/// Rewrite the PHI nodes in an unswitched loop exit basic block.
Expand Down Expand Up @@ -2515,7 +2526,7 @@ static void unswitchNontrivialInvariants(
// the branch in the split block.
if (PartiallyInvariant)
buildPartialInvariantUnswitchConditionalBranch(
*SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU);
*SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU, *BI);
else {
buildPartialUnswitchConditionalBranch(
*SplitBB, Invariants, Direction, *ClonedPH, *LoopPH,
Expand Down
75 changes: 43 additions & 32 deletions llvm/test/Transforms/SimpleLoopUnswitch/partial-unswitch.ll
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
; RUN: opt -passes='loop-mssa(simple-loop-unswitch<nontrivial>),verify<loops>' -S < %s | FileCheck %s

declare void @clobber()

define i32 @partial_unswitch_true_successor(ptr %ptr, i32 %N) {
define i32 @partial_unswitch_true_successor(ptr %ptr, i32 %N) !prof !0 {
; CHECK-LABEL: @partial_unswitch_true_successor(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[PTR:%.*]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i32 [[TMP0]], 100
; CHECK-NEXT: br i1 [[TMP1]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
; CHECK-NEXT: br i1 [[TMP1]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]], !prof [[PROF1:![0-9]+]]
; CHECK: entry.split.us:
; CHECK-NEXT: br label [[LOOP_HEADER_US:%.*]]
; CHECK: loop.header.us:
Expand All @@ -19,7 +19,7 @@ define i32 @partial_unswitch_true_successor(ptr %ptr, i32 %N) {
; CHECK: loop.latch.us:
; CHECK-NEXT: [[C_US:%.*]] = icmp ult i32 [[IV_US]], [[N:%.*]]
; CHECK-NEXT: [[IV_NEXT_US]] = add i32 [[IV_US]], 1
; CHECK-NEXT: br i1 [[C_US]], label [[LOOP_HEADER_US]], label [[EXIT_SPLIT_US:%.*]]
; CHECK-NEXT: br i1 [[C_US]], label [[LOOP_HEADER_US]], label [[EXIT_SPLIT_US:%.*]], !prof [[PROF2:![0-9]+]]
; CHECK: exit.split.us:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: entry.split:
Expand All @@ -28,7 +28,7 @@ define i32 @partial_unswitch_true_successor(ptr %ptr, i32 %N) {
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT]] ], [ [[IV_NEXT:%.*]], [[LOOP_LATCH:%.*]] ]
; CHECK-NEXT: [[LV:%.*]] = load i32, ptr [[PTR]], align 4
; CHECK-NEXT: [[SC:%.*]] = icmp eq i32 [[LV]], 100
; CHECK-NEXT: br i1 [[SC]], label [[NOCLOBBER:%.*]], label [[CLOBBER:%.*]]
; CHECK-NEXT: br i1 [[SC]], label [[NOCLOBBER:%.*]], label [[CLOBBER:%.*]], !prof [[PROF1]]
; CHECK: noclobber:
; CHECK-NEXT: br label [[LOOP_LATCH]]
; CHECK: clobber:
Expand All @@ -37,7 +37,7 @@ define i32 @partial_unswitch_true_successor(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP0:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !prof [[PROF2]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand All @@ -50,7 +50,7 @@ loop.header:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.latch ]
%lv = load i32, ptr %ptr
%sc = icmp eq i32 %lv, 100
br i1 %sc, label %noclobber, label %clobber
br i1 %sc, label %noclobber, label %clobber, !prof !1

noclobber:
br label %loop.latch
Expand All @@ -62,7 +62,7 @@ clobber:
loop.latch:
%c = icmp ult i32 %iv, %N
%iv.next = add i32 %iv, 1
br i1 %c, label %loop.header, label %exit
br i1 %c, label %loop.header, label %exit, !prof !2

exit:
ret i32 10
Expand Down Expand Up @@ -102,7 +102,7 @@ define i32 @partial_unswitch_false_successor(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP2:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP5:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -171,7 +171,7 @@ define i32 @partial_unswtich_gep_load_icmp(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP3:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP6:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -246,7 +246,7 @@ define i32 @partial_unswitch_reduction_phi(ptr %ptr, i32 %N) {
; CHECK-NEXT: [[RED_NEXT]] = phi i32 [ [[ADD_5]], [[CLOBBER]] ], [ [[ADD_10]], [[NOCLOBBER]] ]
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP4:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP7:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: [[RED_NEXT_LCSSA:%.*]] = phi i32 [ [[RED_NEXT]], [[LOOP_LATCH]] ]
; CHECK-NEXT: br label [[EXIT]]
Expand Down Expand Up @@ -325,7 +325,7 @@ define i32 @partial_unswitch_true_successor_noclobber(ptr noalias %ptr.1, ptr no
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP5:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP8:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -637,7 +637,7 @@ define i32 @partial_unswitch_true_successor_preheader_insertion(ptr %ptr, i32 %N
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_LOOPEXIT_SPLIT:%.*]], !llvm.loop [[LOOP6:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_LOOPEXIT_SPLIT:%.*]], !llvm.loop [[LOOP9:![0-9]+]]
; CHECK: exit.loopexit.split:
; CHECK-NEXT: br label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
Expand Down Expand Up @@ -713,7 +713,7 @@ define i32 @partial_unswitch_true_successor_insert_point(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP7:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP10:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -784,7 +784,7 @@ define i32 @partial_unswitch_true_successor_hoist_invariant(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP8:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP11:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -1073,7 +1073,7 @@ define i32 @partial_unswitch_true_to_latch(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP9:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP12:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -1138,7 +1138,7 @@ define i32 @partial_unswitch_exiting_block_with_multiple_unswitch_candidates(i32
; CHECK-NEXT: store i32 [[TMP1:%.*]], ptr [[PTR]], align 16
; CHECK-NEXT: br label [[EXITING]]
; CHECK: exiting:
; CHECK-NEXT: br i1 [[EXIT_COND]], label [[LOOP]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP10:![0-9]+]]
; CHECK-NEXT: br i1 [[EXIT_COND]], label [[LOOP]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP13:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: [[RET_VAL:%.*]] = phi i32 [ 1, [[EXITING]] ]
; CHECK-NEXT: br label [[EXIT]]
Expand Down Expand Up @@ -1249,7 +1249,7 @@ define i32 @partial_unswitch_true_successor_for_cost_calculation(ptr %ptr, i32 %
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP11:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP14:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -1360,7 +1360,7 @@ define i32 @partial_unswitch_true_successor_trunc(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP12:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP15:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -1425,7 +1425,7 @@ define i32 @partial_unswitch_false_successor_trunc(ptr %ptr, i32 %N) {
; CHECK: loop.latch:
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[IV]], [[N]]
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP13:![0-9]+]]
; CHECK-NEXT: br i1 [[C]], label [[LOOP_HEADER]], label [[EXIT_SPLIT:%.*]], !llvm.loop [[LOOP16:![0-9]+]]
; CHECK: exit.split:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
Expand Down Expand Up @@ -1456,15 +1456,26 @@ exit:
ret i32 10
}

; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[UNSWITCH_PARTIAL_DISABLE:![0-9]+]]}
; CHECK: [[UNSWITCH_PARTIAL_DISABLE]] = !{!"llvm.loop.unswitch.partial.disable"}
; CHECK: [[LOOP2]] = distinct !{[[LOOP2]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP3]] = distinct !{[[LOOP3]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP4]] = distinct !{[[LOOP4]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP5]] = distinct !{[[LOOP5]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP6]] = distinct !{[[LOOP6]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP7]] = distinct !{[[LOOP7]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP8]] = distinct !{[[LOOP8]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP9]] = distinct !{[[LOOP9]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP10]] = distinct !{[[LOOP10]], [[UNSWITCH_PARTIAL_DISABLE]]}
; CHECK: [[LOOP11]] = distinct !{[[LOOP11]], [[UNSWITCH_PARTIAL_DISABLE]]}
!0 = !{!"function_entry_count", i32 10}
!1 = !{!"branch_weights", i32 1000, i32 1}
!2 = !{!"branch_weights", i32 100, i32 3}

;.
; CHECK: [[META0:![0-9]+]] = !{!"function_entry_count", i32 10}
; CHECK: [[PROF1]] = !{!"branch_weights", i32 1000, i32 1}
; CHECK: [[PROF2]] = !{!"branch_weights", i32 100, i32 3}
; CHECK: [[LOOP3]] = distinct !{[[LOOP3]], [[META4:![0-9]+]]}
; CHECK: [[META4]] = !{!"llvm.loop.unswitch.partial.disable"}
; CHECK: [[LOOP5]] = distinct !{[[LOOP5]], [[META4]]}
; CHECK: [[LOOP6]] = distinct !{[[LOOP6]], [[META4]]}
; CHECK: [[LOOP7]] = distinct !{[[LOOP7]], [[META4]]}
; CHECK: [[LOOP8]] = distinct !{[[LOOP8]], [[META4]]}
; CHECK: [[LOOP9]] = distinct !{[[LOOP9]], [[META4]]}
; CHECK: [[LOOP10]] = distinct !{[[LOOP10]], [[META4]]}
; CHECK: [[LOOP11]] = distinct !{[[LOOP11]], [[META4]]}
; CHECK: [[LOOP12]] = distinct !{[[LOOP12]], [[META4]]}
; CHECK: [[LOOP13]] = distinct !{[[LOOP13]], [[META4]]}
; CHECK: [[LOOP14]] = distinct !{[[LOOP14]], [[META4]]}
; CHECK: [[LOOP15]] = distinct !{[[LOOP15]], [[META4]]}
; CHECK: [[LOOP16]] = distinct !{[[LOOP16]], [[META4]]}
;.
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