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[profcheck] Add unknown branch weight for inlined memchr calls. #160964

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Merged
merged 2 commits into from
Sep 30, 2025
Merged

[profcheck] Add unknown branch weight for inlined memchr calls. #160964

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3aa7f6f
[profcheck] Add unknown branch weight for inlined memchr calls.
Sep 26, 2025
87762a6
Merge branch 'main' into fixup/no-prof-AggressiveInstCombine-memchr
mtrofin Sep 29, 2025
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4 changes: 4 additions & 0 deletions llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1350,6 +1350,10 @@ static bool foldMemChr(CallInst *Call, DomTreeUpdater *DTU,
BB->getTerminator()->eraseFromParent();
SwitchInst *SI = IRB.CreateSwitch(
IRB.CreateTrunc(Call->getArgOperand(1), ByteTy), BBNext, N);
// We can't know the precise weights here, as they would depend on the value
// distribution of Call->getArgOperand(1). So we just mark it as "unknown".
setExplicitlyUnknownBranchWeightsIfProfiled(*SI, *Call->getFunction(),
DEBUG_TYPE);
Type *IndexTy = DL.getIndexType(Call->getType());
SmallVector<DominatorTree::UpdateType, 8> Updates;

Expand Down
51 changes: 32 additions & 19 deletions llvm/test/Transforms/AggressiveInstCombine/memchr.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,10 @@

declare ptr @memchr(ptr, i32, i64)

define i1 @test_memchr_null(i32 %x) {
define i1 @test_memchr_null(i32 %x) !prof !0 {
; CHECK-LABEL: define i1 @test_memchr_null(
; CHECK-SAME: i32 [[X:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]])
; CHECK: !prof [[PROF_0:![0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i32 [[X]] to i8
; CHECK-NEXT: switch i8 [[TMP0]], label %[[ENTRY_SPLIT:.*]] [
Expand Down Expand Up @@ -40,9 +41,10 @@ entry:
ret i1 %isnull
}

define ptr @test_memchr(i32 %x) {
define ptr @test_memchr(i32 %x) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr(
; CHECK-SAME: i32 [[X:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i32 [[X]] to i8
; CHECK-NEXT: switch i8 [[TMP0]], label %[[ENTRY_SPLIT:.*]] [
Expand Down Expand Up @@ -72,16 +74,17 @@ entry:
ret ptr %memchr
}

define ptr @test_memchr_smaller_n(i32 %x) {
define ptr @test_memchr_smaller_n(i32 %x) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_smaller_n(
; CHECK-SAME: i32 [[X:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i32 [[X]] to i8
; CHECK-NEXT: switch i8 [[TMP0]], label %[[ENTRY_SPLIT:.*]] [
; CHECK-NEXT: i8 48, label %[[MEMCHR_CASE:.*]]
; CHECK-NEXT: i8 49, label %[[MEMCHR_CASE1:.*]]
; CHECK-NEXT: i8 0, label %[[MEMCHR_CASE2:.*]]
; CHECK-NEXT: ]
; CHECK-NEXT: ], !prof [[PROF_1:![0-9]+]]
; CHECK: [[MEMCHR_CASE]]:
; CHECK-NEXT: br label %[[MEMCHR_SUCCESS:.*]]
; CHECK: [[MEMCHR_CASE1]]:
Expand All @@ -103,9 +106,10 @@ entry:

; negative tests

define ptr @test_memchr_larger_n(i32 %x) {
define ptr @test_memchr_larger_n(i32 %x) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_larger_n(
; CHECK-SAME: i32 [[X:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr @str, i32 [[X]], i64 6)
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -115,9 +119,10 @@ entry:
ret ptr %memchr
}

define ptr @test_memchr_non_constant(i32 %x, ptr %str) {
define ptr @test_memchr_non_constant(i32 %x, ptr %str) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_non_constant(
; CHECK-SAME: i32 [[X:%.*]], ptr [[STR:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]], ptr [[STR:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr [[STR]], i32 [[X]], i64 5)
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -127,8 +132,9 @@ entry:
ret ptr %memchr
}

define ptr @test_memchr_constant_ch() {
; CHECK-LABEL: define ptr @test_memchr_constant_ch() {
define ptr @test_memchr_constant_ch() !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_constant_ch()
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr @str, i32 49, i64 5)
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -138,9 +144,10 @@ entry:
ret ptr %memchr
}

define ptr @test_memchr_dynamic_n(i32 %x, i32 %y) {
define ptr @test_memchr_dynamic_n(i32 %x, i32 %y) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_dynamic_n(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr @str, i32 [[X]], i32 [[Y]])
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -150,9 +157,10 @@ entry:
ret ptr %memchr
}

define ptr @test_memchr_long(i32 %x) {
define ptr @test_memchr_long(i32 %x) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_long(
; CHECK-SAME: i32 [[X:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr @str_long, i32 [[X]], i64 8)
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -163,9 +171,10 @@ entry:
}

; We want to check that the compiler still calls memchr if the length is non-constant:
define ptr @test_memchr_non_constant_length2(i32 %x, i64 %len) {
define ptr @test_memchr_non_constant_length2(i32 %x, i64 %len) !prof !0 {
; CHECK-LABEL: define ptr @test_memchr_non_constant_length2(
; CHECK-SAME: i32 [[X:%.*]], i64 [[LEN:%.*]]) {
; CHECK-SAME: i32 [[X:%.*]], i64 [[LEN:%.*]])
; CHECK: !prof [[PROF_0]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[MEMCHR:%.*]] = call ptr @memchr(ptr @str, i32 [[X]], i64 [[LEN]])
; CHECK-NEXT: ret ptr [[MEMCHR]]
Expand All @@ -174,3 +183,7 @@ entry:
%memchr = call ptr @memchr(ptr @str, i32 %x, i64 %len)
ret ptr %memchr
}

!0 = !{!"function_entry_count", i64 1000}
; CHECK: [[PROF_0]] = !{!"function_entry_count", i64 1000}
; CHECK: [[PROF_1]] = !{!"unknown", !"aggressive-instcombine"}
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nit: missing EOF line.