https://github.com/mtrofin created
https://github.com/llvm/llvm-project/pull/153738
None
>From 5c51af5145fa3dae57ec5a56a6f3d5c3c1f53679 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtro...@google.com>
Date: Thu, 14 Aug 2025 20:26:48 -0700
Subject: [PATCH] [JTS] Use common branch weigth downscaling
---
.../Transforms/Scalar/JumpTableToSwitch.cpp | 14 ++--
.../Transforms/JumpTableToSwitch/basic.ll | 81 ++++++++++++++++---
2 files changed, 78 insertions(+), 17 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
index 9dde131185cf8..9d915d0d967e5 100644
--- a/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpTableToSwitch.cpp
@@ -159,6 +159,10 @@ expandToSwitch(CallBase *CB, const JumpTableTy &JT,
DomTreeUpdater &DTU,
DTUpdates.push_back({DominatorTree::Insert, B, Tail});
CallBase *Call = cast<CallBase>(CB->clone());
+ // The MD_prof metadata (VP kind), if it existed, can be dropped, it
doesn't
+ // make sense on a direct call. Note that the values are used for the
branch
+ // weights of the switch.
+ Call->setMetadata(LLVMContext::MD_prof, nullptr);
Call->setCalledFunction(Func);
Call->insertInto(B, B->end());
Switch->addCase(
@@ -180,14 +184,8 @@ expandToSwitch(CallBase *CB, const JumpTableTy &JT,
DomTreeUpdater &DTU,
if (HadProfile && !ProfcheckDisableMetadataFixes) {
// At least one of the targets must've been taken.
assert(llvm::any_of(BranchWeights, [](uint64_t V) { return V != 0; }));
- // FIXME: this duplicates logic in instrumentation. Note: since there's at
- // least a nonzero and these are unsigned values, it follows MaxBW != 0.
- uint64_t MaxBW = *llvm::max_element(BranchWeights);
- SmallVector<uint32_t> ScaledBranchWeights(
- llvm::map_range(BranchWeights, [MaxBW](uint64_t V) {
- return static_cast<uint32_t>(V / MaxBW);
- }));
- setBranchWeights(*Switch, ScaledBranchWeights, /*IsExpected=*/false);
+ setBranchWeights(*Switch, downscaleWeights(BranchWeights),
+ /*IsExpected=*/false);
} else
setExplicitlyUnknownBranchWeights(*Switch);
if (PHI)
diff --git a/llvm/test/Transforms/JumpTableToSwitch/basic.ll
b/llvm/test/Transforms/JumpTableToSwitch/basic.ll
index 577c2adaf5afa..e3c032b9d4bf7 100644
--- a/llvm/test/Transforms/JumpTableToSwitch/basic.ll
+++ b/llvm/test/Transforms/JumpTableToSwitch/basic.ll
@@ -1,14 +1,39 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
UTC_ARGS: --version 4
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
UTC_ARGS: --check-globals all --version 4
; RUN: opt < %s -passes=jump-table-to-switch -verify-dom-info -S | FileCheck %s
; RUN: opt < %s -passes=jump-table-to-switch
-jump-table-to-switch-size-threshold=0 -verify-dom-info -S | FileCheck %s
--check-prefix=THRESHOLD-0
@func_array = constant [2 x ptr] [ptr @func0, ptr @func1]
+;.
+; CHECK: @func_array = constant [2 x ptr] [ptr @func0, ptr @func1]
+; CHECK: @void_func_array = constant [2 x ptr] [ptr @void_func0, ptr
@void_func1]
+; CHECK: @func_array_addrspace_42 = addrspace(42) constant [2 x ptr
addrspace(42)] [ptr addrspace(42) @func0_addrspace_42, ptr addrspace(42)
@func1_addrspace_42]
+;.
+; THRESHOLD-0: @func_array = constant [2 x ptr] [ptr @func0, ptr @func1]
+; THRESHOLD-0: @void_func_array = constant [2 x ptr] [ptr @void_func0, ptr
@void_func1]
+; THRESHOLD-0: @func_array_addrspace_42 = addrspace(42) constant [2 x ptr
addrspace(42)] [ptr addrspace(42) @func0_addrspace_42, ptr addrspace(42)
@func1_addrspace_42]
+;.
define i32 @func0() !guid !0 {
+; CHECK-LABEL: define i32 @func0(
+; CHECK-SAME: ) !guid [[META0:![0-9]+]] {
+; CHECK-NEXT: ret i32 1
+;
+; THRESHOLD-0-LABEL: define i32 @func0(
+; THRESHOLD-0-SAME: ) !guid [[META0:![0-9]+]] {
+; THRESHOLD-0-NEXT: ret i32 1
+;
ret i32 1
}
define i32 @func1() !guid !1 {
+; CHECK-LABEL: define i32 @func1(
+; CHECK-SAME: ) !guid [[META1:![0-9]+]] {
+; CHECK-NEXT: ret i32 2
+;
+; THRESHOLD-0-LABEL: define i32 @func1(
+; THRESHOLD-0-SAME: ) !guid [[META1:![0-9]+]] {
+; THRESHOLD-0-NEXT: ret i32 2
+;
ret i32 2
}
@@ -20,7 +45,7 @@ define i32 @function_with_jump_table(i32 %index) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_0:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_1:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF2:![0-9]+]]
; CHECK: default.switch.case.unreachable:
; CHECK-NEXT: unreachable
; CHECK: call.0:
@@ -37,7 +62,7 @@ define i32 @function_with_jump_table(i32 %index) {
; THRESHOLD-0-SAME: i32 [[INDEX:%.*]]) {
; THRESHOLD-0-NEXT: [[GEP:%.*]] = getelementptr inbounds [2 x ptr], ptr
@func_array, i32 0, i32 [[INDEX]]
; THRESHOLD-0-NEXT: [[FUNC_PTR:%.*]] = load ptr, ptr [[GEP]], align 8
-; THRESHOLD-0-NEXT: [[RESULT:%.*]] = call i32 [[FUNC_PTR]]()
+; THRESHOLD-0-NEXT: [[RESULT:%.*]] = call i32 [[FUNC_PTR]](), !prof
[[PROF2:![0-9]+]]
; THRESHOLD-0-NEXT: ret i32 [[RESULT]]
;
%gep = getelementptr inbounds [2 x ptr], ptr @func_array, i32 0, i32 %index
@@ -54,7 +79,7 @@ define i32 @basic_block_splitted_twice(i32 %index) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_0:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_1:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF3:![0-9]+]]
; CHECK: default.switch.case.unreachable:
; CHECK-NEXT: unreachable
; CHECK: call.0:
@@ -70,7 +95,7 @@ define i32 @basic_block_splitted_twice(i32 %index) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE1:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_02:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_13:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF3]]
; CHECK: default.switch.case.unreachable1:
; CHECK-NEXT: unreachable
; CHECK: call.02:
@@ -106,10 +131,22 @@ define i32 @basic_block_splitted_twice(i32 %index) {
}
define void @void_func0() {
+; CHECK-LABEL: define void @void_func0() {
+; CHECK-NEXT: ret void
+;
+; THRESHOLD-0-LABEL: define void @void_func0() {
+; THRESHOLD-0-NEXT: ret void
+;
ret void
}
define void @void_func1() {
+; CHECK-LABEL: define void @void_func1() {
+; CHECK-NEXT: ret void
+;
+; THRESHOLD-0-LABEL: define void @void_func1() {
+; THRESHOLD-0-NEXT: ret void
+;
ret void
}
@@ -123,7 +160,7 @@ define void @void_function_with_jump_table(i32 %index) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_0:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_1:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF3]]
; CHECK: default.switch.case.unreachable:
; CHECK-NEXT: unreachable
; CHECK: call.0:
@@ -156,7 +193,7 @@ define void
@void_function_with_jump_table_and_call_site_attr(i32 %index) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_0:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_1:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF3]]
; CHECK: default.switch.case.unreachable:
; CHECK-NEXT: unreachable
; CHECK: call.0:
@@ -183,10 +220,22 @@ define void
@void_function_with_jump_table_and_call_site_attr(i32 %index) {
define i32 @func0_addrspace_42() addrspace(42) {
+; CHECK-LABEL: define i32 @func0_addrspace_42() addrspace(42) {
+; CHECK-NEXT: ret i32 1
+;
+; THRESHOLD-0-LABEL: define i32 @func0_addrspace_42() addrspace(42) {
+; THRESHOLD-0-NEXT: ret i32 1
+;
ret i32 1
}
define i32 @func1_addrspace_42() addrspace(42) {
+; CHECK-LABEL: define i32 @func1_addrspace_42() addrspace(42) {
+; CHECK-NEXT: ret i32 2
+;
+; THRESHOLD-0-LABEL: define i32 @func1_addrspace_42() addrspace(42) {
+; THRESHOLD-0-NEXT: ret i32 2
+;
ret i32 2
}
@@ -200,7 +249,7 @@ define i32 @function_with_jump_table_addrspace_42(i32
%index) addrspace(42) {
; CHECK-NEXT: switch i32 [[INDEX]], label
[[DEFAULT_SWITCH_CASE_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[CALL_0:%.*]]
; CHECK-NEXT: i32 1, label [[CALL_1:%.*]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: ], !prof [[PROF3]]
; CHECK: default.switch.case.unreachable:
; CHECK-NEXT: unreachable
; CHECK: call.0:
@@ -228,4 +277,18 @@ define i32 @function_with_jump_table_addrspace_42(i32
%index) addrspace(42) {
!0 = !{i64 5678}
!1 = !{i64 5555}
-!2 = !{!"VP", i32 0, i64 25, i64 5678, i64 20, i64 5555, i64 5}
\ No newline at end of file
+!2 = !{!"VP", i32 0, i64 25, i64 5678, i64 20, i64 5555, i64 5}
+;.
+; CHECK: attributes #[[ATTR0]] = { nounwind }
+;.
+; THRESHOLD-0: attributes #[[ATTR0]] = { nounwind }
+;.
+; CHECK: [[META0]] = !{i64 5678}
+; CHECK: [[META1]] = !{i64 5555}
+; CHECK: [[PROF2]] = !{!"branch_weights", i32 0, i32 20, i32 5}
+; CHECK: [[PROF3]] = !{!"unknown"}
+;.
+; THRESHOLD-0: [[META0]] = !{i64 5678}
+; THRESHOLD-0: [[META1]] = !{i64 5555}
+; THRESHOLD-0: [[PROF2]] = !{!"VP", i32 0, i64 25, i64 5678, i64 20, i64 5555,
i64 5}
+;.
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