[llvm-branch-commits] [llvm] [SLU][profcheck] create likely branch weights for guard->branch (PR #164271)
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Mon Oct 20 08:26:54 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Mircea Trofin (mtrofin)
<details>
<summary>Changes</summary>
---
Full diff: https://github.com/llvm/llvm-project/pull/164271.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp (+9-3)
- (modified) llvm/test/Transforms/SimpleLoopUnswitch/guards.ll (+130-51)
``````````diff
diff --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index 8fb9b7edbadec..28f6af7769183 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -40,6 +40,7 @@
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/ProfDataUtils.h"
@@ -2823,9 +2824,14 @@ static BranchInst *turnGuardIntoBranch(IntrinsicInst *GI, Loop &L,
MSSAU->getMemorySSA()->verifyMemorySSA();
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
- Instruction *DeoptBlockTerm =
- SplitBlockAndInsertIfThen(GI->getArgOperand(0), GI, true,
- GI->getMetadata(LLVMContext::MD_prof), &DTU, &LI);
+ // llvm.experimental.guard doesn't have branch weights. We can assume,
+ // however, that the deopt path is unlikely.
+ Instruction *DeoptBlockTerm = SplitBlockAndInsertIfThen(
+ GI->getArgOperand(0), GI, true,
+ !ProfcheckDisableMetadataFixes && EstimateProfile
+ ? MDBuilder(GI->getContext()).createUnlikelyBranchWeights()
+ : nullptr,
+ &DTU, &LI);
BranchInst *CheckBI = cast<BranchInst>(CheckBB->getTerminator());
// SplitBlockAndInsertIfThen inserts control flow that branches to
// DeoptBlockTerm if the condition is true. We want the opposite.
diff --git a/llvm/test/Transforms/SimpleLoopUnswitch/guards.ll b/llvm/test/Transforms/SimpleLoopUnswitch/guards.ll
index 533b1f691f5ad..e83047e397d3d 100644
--- a/llvm/test/Transforms/SimpleLoopUnswitch/guards.ll
+++ b/llvm/test/Transforms/SimpleLoopUnswitch/guards.ll
@@ -1,26 +1,34 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: -p --version 5
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: -p --check-globals all --version 5
; RUN: opt -passes='loop(simple-loop-unswitch<nontrivial>),verify<loops>' -simple-loop-unswitch-guards -S < %s | FileCheck %s
; RUN: opt -passes='simple-loop-unswitch<nontrivial>' -simple-loop-unswitch-guards -S < %s | FileCheck %s
; RUN: opt -passes='loop-mssa(simple-loop-unswitch<nontrivial>),verify<loops>' -simple-loop-unswitch-guards -verify-memoryssa -verify-loop-info -S < %s | FileCheck %s
declare void @llvm.experimental.guard(i1, ...)
-define void @test_simple_case(i1 %cond, i32 %N) {
-; CHECK-LABEL: @test_simple_case(
+define void @test_simple_case(i1 %cond, i32 %N) !prof !0 {
+; CHECK-LABEL: define void @test_simple_case(i1 %cond, i32 %N) !prof !0 {
; CHECK-NEXT: entry:
-; CHECK-NEXT: br i1 [[COND:%.*]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
+; CHECK-NEXT: br i1 %cond, label %entry.split.us, label %entry.split, !prof !1
; CHECK: entry.split.us:
-; CHECK-NEXT: br label [[LOOP_US:%.*]]
+; CHECK-NEXT: br label %loop.us
; CHECK: loop.us:
-; CHECK-NEXT: [[IV_US:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT_US]] ], [ [[IV_NEXT_US:%.*]], [[GUARDED_US:%.*]] ]
-; CHECK-NEXT: br label [[GUARDED_US]]
+; CHECK-NEXT: %iv.us = phi i32 [ 0, %entry.split.us ], [ %iv.next.us, %guarded.us ]
+; CHECK-NEXT: br label %guarded.us
; CHECK: guarded.us:
-; CHECK-NEXT: [[IV_NEXT_US]] = add i32 [[IV_US]], 1
-; CHECK-NEXT: [[LOOP_COND_US:%.*]] = icmp slt i32 [[IV_NEXT_US]], [[N:%.*]]
-; CHECK-NEXT: br i1 [[LOOP_COND_US]], label [[LOOP_US]], label [[EXIT_SPLIT_US:%.*]]
+; CHECK-NEXT: %iv.next.us = add i32 %iv.us, 1
+; CHECK-NEXT: %loop.cond.us = icmp slt i32 %iv.next.us, %N
+; CHECK-NEXT: br i1 %loop.cond.us, label %loop.us, label %exit.split.us
+; CHECK: exit.split.us:
+; CHECK-NEXT: br label %exit
+; CHECK: entry.split:
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: br label %deopt
; CHECK: deopt:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
+; CHECK: exit:
+; CHECK-NEXT: ret void
;
entry:
@@ -38,25 +46,39 @@ exit:
}
define void @test_two_guards(i1 %cond1, i1 %cond2, i32 %N) {
-; CHECK-LABEL: @test_two_guards(
+; CHECK-LABEL: define void @test_two_guards(i1 %cond1, i1 %cond2, i32 %N) {
; CHECK-NEXT: entry:
-; CHECK-NEXT: br i1 [[COND1:%.*]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
+; CHECK-NEXT: br i1 %cond1, label %entry.split.us, label %entry.split, !prof !1
; CHECK: entry.split.us:
-; CHECK-NEXT: br i1 [[COND2:%.*]], label [[ENTRY_SPLIT_US_SPLIT_US:%.*]], label [[ENTRY_SPLIT_US_SPLIT:%.*]]
+; CHECK-NEXT: br i1 %cond2, label %entry.split.us.split.us, label %entry.split.us.split, !prof !1
; CHECK: entry.split.us.split.us:
-; CHECK-NEXT: br label [[LOOP_US_US:%.*]]
+; CHECK-NEXT: br label %loop.us.us
; CHECK: loop.us.us:
-; CHECK-NEXT: [[IV_US_US:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT_US_SPLIT_US]] ], [ [[IV_NEXT_US_US:%.*]], [[GUARDED_US2:%.*]] ]
-; CHECK-NEXT: br label [[GUARDED_US_US:%.*]]
+; CHECK-NEXT: %iv.us.us = phi i32 [ 0, %entry.split.us.split.us ], [ %iv.next.us.us, %guarded.us2 ]
+; CHECK-NEXT: br label %guarded.us.us
; CHECK: guarded.us.us:
-; CHECK-NEXT: br label [[GUARDED_US2]]
+; CHECK-NEXT: br label %guarded.us2
; CHECK: guarded.us2:
-; CHECK-NEXT: [[IV_NEXT_US_US]] = add i32 [[IV_US_US]], 1
-; CHECK-NEXT: [[LOOP_COND_US_US:%.*]] = icmp slt i32 [[IV_NEXT_US_US]], [[N:%.*]]
-; CHECK-NEXT: br i1 [[LOOP_COND_US_US]], label [[LOOP_US_US]], label [[EXIT_SPLIT_US_SPLIT_US:%.*]]
+; CHECK-NEXT: %iv.next.us.us = add i32 %iv.us.us, 1
+; CHECK-NEXT: %loop.cond.us.us = icmp slt i32 %iv.next.us.us, %N
+; CHECK-NEXT: br i1 %loop.cond.us.us, label %loop.us.us, label %exit.split.us.split.us
+; CHECK: exit.split.us.split.us:
+; CHECK-NEXT: br label %exit.split.us
+; CHECK: entry.split.us.split:
+; CHECK-NEXT: br label %loop.us
+; CHECK: loop.us:
+; CHECK-NEXT: br label %guarded.us
+; CHECK: guarded.us:
+; CHECK-NEXT: br label %deopt1
; CHECK: deopt1:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
+; CHECK: exit.split.us:
+; CHECK-NEXT: br label %exit
+; CHECK: entry.split:
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: br label %deopt
; CHECK: deopt:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
@@ -80,35 +102,45 @@ exit:
}
define void @test_conditional_guards(i1 %cond, i32 %N) {
-; CHECK-LABEL: @test_conditional_guards(
+; CHECK-LABEL: define void @test_conditional_guards(i1 %cond, i32 %N) {
; CHECK-NEXT: entry:
-; CHECK-NEXT: [[FROZEN:%.+]] = freeze i1 [[COND:%.*]]
-; CHECK-NEXT: br i1 [[FROZEN]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
+; CHECK-NEXT: %cond.fr = freeze i1 %cond
+; CHECK-NEXT: br i1 %cond.fr, label %entry.split.us, label %entry.split, !prof !1
; CHECK: entry.split.us:
-; CHECK-NEXT: br label [[LOOP_US:%.*]]
+; CHECK-NEXT: br label %loop.us
; CHECK: loop.us:
-; CHECK-NEXT: [[IV_US:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT_US]] ], [ [[IV_NEXT_US:%.*]], [[BACKEDGE_US:%.*]] ]
-; CHECK-NEXT: [[CONDITION_US:%.*]] = icmp eq i32 [[IV_US]], 123
-; CHECK-NEXT: br i1 [[CONDITION_US]], label [[GUARD_US:%.*]], label [[BACKEDGE_US]]
+; CHECK-NEXT: %iv.us = phi i32 [ 0, %entry.split.us ], [ %iv.next.us, %backedge.us ]
+; CHECK-NEXT: %condition.us = icmp eq i32 %iv.us, 123
+; CHECK-NEXT: br i1 %condition.us, label %guard.us, label %backedge.us
; CHECK: guard.us:
-; CHECK-NEXT: br label [[GUARDED_US:%.*]]
+; CHECK-NEXT: br label %guarded.us
; CHECK: backedge.us:
-; CHECK-NEXT: [[IV_NEXT_US]] = add i32 [[IV_US]], 1
-; CHECK-NEXT: [[LOOP_COND_US:%.*]] = icmp slt i32 [[IV_NEXT_US]], [[N:%.*]]
-; CHECK-NEXT: br i1 [[LOOP_COND_US]], label [[LOOP_US]], label [[EXIT_SPLIT_US:%.*]]
+; CHECK-NEXT: %iv.next.us = add i32 %iv.us, 1
+; CHECK-NEXT: %loop.cond.us = icmp slt i32 %iv.next.us, %N
+; CHECK-NEXT: br i1 %loop.cond.us, label %loop.us, label %exit.split.us
+; CHECK: guarded.us:
+; CHECK-NEXT: br label %backedge.us
+; CHECK: exit.split.us:
+; CHECK-NEXT: br label %exit
+; CHECK: entry.split:
+; CHECK-NEXT: br label %loop
; CHECK: loop:
-; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
-; CHECK-NEXT: [[CONDITION:%.*]] = icmp eq i32 [[IV]], 123
-; CHECK-NEXT: br i1 [[CONDITION]], label [[GUARD:%.*]], label [[BACKEDGE]]
+; CHECK-NEXT: %iv = phi i32 [ 0, %entry.split ], [ %iv.next, %backedge ]
+; CHECK-NEXT: %condition = icmp eq i32 %iv, 123
+; CHECK-NEXT: br i1 %condition, label %guard, label %backedge
; CHECK: guard:
-; CHECK-NEXT: br label [[DEOPT:%.*]]
+; CHECK-NEXT: br label %deopt
; CHECK: deopt:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
; CHECK: backedge:
-; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
-; CHECK-NEXT: [[LOOP_COND:%.*]] = icmp slt i32 [[IV_NEXT]], [[N]]
-; CHECK-NEXT: br i1 [[LOOP_COND]], label %loop, label [[EXIT_SPLIT:%.*]]
+; CHECK-NEXT: %iv.next = add i32 %iv, 1
+; CHECK-NEXT: %loop.cond = icmp slt i32 %iv.next, %N
+; CHECK-NEXT: br i1 %loop.cond, label %loop, label %exit.split
+; CHECK: exit.split:
+; CHECK-NEXT: br label %exit
+; CHECK: exit:
+; CHECK-NEXT: ret void
;
entry:
@@ -135,7 +167,7 @@ exit:
define void @test_nested_loop(i1 %cond, i32 %N, i1 %arg) {
; CHECK-LABEL: define void @test_nested_loop(i1 %cond, i32 %N, i1 %arg) {
; CHECK-NEXT: entry:
-; CHECK-NEXT: br i1 %cond, label %entry.split, label %outer_loop.split
+; CHECK-NEXT: br i1 %cond, label %entry.split, label %outer_loop.split, !prof !1
; CHECK: entry.split:
; CHECK-NEXT: br i1 %arg, label %entry.split.split.us, label %entry.split.split
; CHECK: entry.split.split.us:
@@ -204,17 +236,49 @@ exit:
}
define void @test_sibling_loops(i1 %cond1, i1 %cond2, i32 %N) {
-; CHECK-LABEL: @test_sibling_loops(
+; CHECK-LABEL: define void @test_sibling_loops(i1 %cond1, i1 %cond2, i32 %N) {
; CHECK-NEXT: entry:
-; CHECK-NEXT: br i1 [[COND1:%.*]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
-; CHECK: [[IV1_US:%.*]] = phi i32 [ 0, [[ENTRY_SPLIT_US]] ], [ [[IV1_NEXT_US:%.*]], [[GUARDED_US:%.*]] ]
-; CHECK-NEXT: br label [[GUARDED_US]]
-; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
+; CHECK-NEXT: br i1 %cond1, label %entry.split.us, label %entry.split, !prof !1
+; CHECK: entry.split.us:
+; CHECK-NEXT: br label %loop1.us
+; CHECK: loop1.us:
+; CHECK-NEXT: %iv1.us = phi i32 [ 0, %entry.split.us ], [ %iv1.next.us, %guarded.us ]
+; CHECK-NEXT: br label %guarded.us
+; CHECK: guarded.us:
+; CHECK-NEXT: %iv1.next.us = add i32 %iv1.us, 1
+; CHECK-NEXT: %loop1.cond.us = icmp slt i32 %iv1.next.us, %N
+; CHECK-NEXT: br i1 %loop1.cond.us, label %loop1.us, label %between.split.us
+; CHECK: between.split.us:
+; CHECK-NEXT: br label %between
+; CHECK: entry.split:
+; CHECK-NEXT: br label %loop1
+; CHECK: loop1:
+; CHECK-NEXT: br label %deopt
+; CHECK: deopt:
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
-; CHECK: [[IV2_US:%.*]] = phi i32 [ 0, [[BETWEEN:%.*]] ], [ [[IV1_NEXT_US2:%.*]], [[GUARDED_US2:%.*]] ]
-; CHECK-NEXT: br label [[GUARDED_US2]]
-; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
+; CHECK: between:
+; CHECK-NEXT: br i1 %cond2, label %between.split.us2, label %between.split, !prof !1
+; CHECK: between.split.us2:
+; CHECK-NEXT: br label %loop2.us
+; CHECK: loop2.us:
+; CHECK-NEXT: %iv2.us = phi i32 [ 0, %between.split.us2 ], [ %iv2.next.us, %guarded.us3 ]
+; CHECK-NEXT: br label %guarded.us3
+; CHECK: guarded.us3:
+; CHECK-NEXT: %iv2.next.us = add i32 %iv2.us, 1
+; CHECK-NEXT: %loop2.cond.us = icmp slt i32 %iv2.next.us, %N
+; CHECK-NEXT: br i1 %loop2.cond.us, label %loop2.us, label %exit.split.us
+; CHECK: exit.split.us:
+; CHECK-NEXT: br label %exit
+; CHECK: between.split:
+; CHECK-NEXT: br label %loop2
+; CHECK: loop2:
+; CHECK-NEXT: br label %deopt1
+; CHECK: deopt1:
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
+; CHECK: exit:
+; CHECK-NEXT: ret void
;
entry:
@@ -242,11 +306,20 @@ exit:
}
; Check that we don't do anything because of cleanuppad.
-; CHECK-LABEL: @test_cleanuppad(
-; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
-; CHECK-NOT: call void (i1, ...) @llvm.experimental.guard(
define void @test_cleanuppad(i1 %cond, i32 %N) personality ptr @__CxxFrameHandler3 {
-
+; CHECK-LABEL: define void @test_cleanuppad(i1 %cond, i32 %N) personality ptr @__CxxFrameHandler3 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label %loop
+; CHECK: loop:
+; CHECK-NEXT: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
+; CHECK-NEXT: %iv.next = add i32 %iv, 1
+; CHECK-NEXT: invoke void @may_throw(i32 %iv)
+; CHECK-NEXT: to label %loop unwind label %exit
+; CHECK: exit:
+; CHECK-NEXT: %cp = cleanuppad within none []
+; CHECK-NEXT: cleanupret from %cp unwind to caller
+;
entry:
br label %loop
@@ -264,3 +337,9 @@ exit:
declare void @may_throw(i32 %i)
declare i32 @__CxxFrameHandler3(...)
+
+!0 = !{!"function_entry_count", i32 10}
+;.
+; CHECK: !0 = !{!"function_entry_count", i32 10}
+; CHECK: !1 = !{!"branch_weights", i32 1048575, i32 1}
+;.
``````````
</details>
https://github.com/llvm/llvm-project/pull/164271
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