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llvm-project/llvm/test/Transforms/SimpleLoopUnswitch/guards.ll
Antonio Frighetto 33761df961
Revert "[SimpleLoopUnswitch] Record loops from unswitching non-trivial conditions" 
This reverts commit e9de32fd159d30cfd6fcc861b57b7e99ec2742ab due to
multiple performance regressions observed across downstream Numba
benchmarks (https://github.com/llvm/llvm-project/issues/138509#issuecomment-3193855772).

While avoiding non-trivial unswitches on newly-cloned loops helps
mitigate the pathological case reported in https://github.com/llvm/llvm-project/issues/138509,
it may as well make the IR less friendly to vectorization / loop-
canonicalization (in the test reported, previously no select with
loop-carried dependence existed in the new specialized loops),
leading the abovementioned approach to be reconsidered.
2025-08-18 17:40:08 +02:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: -p --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(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
; CHECK: entry.split.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: 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: deopt:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
%iv.next = add i32 %iv, 1
%loop.cond = icmp slt i32 %iv.next, %N
br i1 %loop.cond, label %loop, label %exit
exit:
ret void
}
define void @test_two_guards(i1 %cond1, i1 %cond2, i32 %N) {
; CHECK-LABEL: @test_two_guards(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[COND1:%.*]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
; CHECK: entry.split.us:
; CHECK-NEXT: br i1 [[COND2:%.*]], label [[ENTRY_SPLIT_US_SPLIT_US:%.*]], label [[ENTRY_SPLIT_US_SPLIT:%.*]]
; CHECK: entry.split.us.split.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: guarded.us.us:
; 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: deopt1:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
; CHECK: deopt:
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
; CHECK-NEXT: unreachable
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ]
%iv.next = add i32 %iv, 1
%loop.cond = icmp slt i32 %iv.next, %N
br i1 %loop.cond, label %loop, label %exit
exit:
ret void
}
define void @test_conditional_guards(i1 %cond, i32 %N) {
; CHECK-LABEL: @test_conditional_guards(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[FROZEN:%.+]] = freeze i1 [[COND:%.*]]
; CHECK-NEXT: br i1 [[FROZEN]], label [[ENTRY_SPLIT_US:%.*]], label [[ENTRY_SPLIT:%.*]]
; CHECK: entry.split.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: guard.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: 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: guard:
; 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:%.*]]
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
%condition = icmp eq i32 %iv, 123
br i1 %condition, label %guard, label %backedge
guard:
call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
br label %backedge
backedge:
%iv.next = add i32 %iv, 1
%loop.cond = icmp slt i32 %iv.next, %N
br i1 %loop.cond, label %loop, label %exit
exit:
ret void
}
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: entry.split:
; CHECK-NEXT: br i1 %arg, label %entry.split.split.us, label %entry.split.split
; CHECK: entry.split.split.us:
; CHECK-NEXT: br label %outer_loop.us
; CHECK: outer_loop.us:
; CHECK-NEXT: br label %outer_loop.split.us.us
; CHECK: outer_backedge.us:
; CHECK-NEXT: br label %outer_loop.us
; CHECK: outer_loop.split.us.us:
; CHECK-NEXT: br label %loop.us.us
; CHECK: loop.us.us:
; CHECK-NEXT: %iv.us.us = phi i32 [ 0, %outer_loop.split.us.us ], [ %iv.next.us.us, %guarded.us.us ]
; CHECK-NEXT: br label %guarded.us.us
; CHECK: guarded.us.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 %outer_backedge.split.us.us
; CHECK: outer_backedge.split.us.us:
; CHECK-NEXT: br label %outer_backedge.us
; CHECK: entry.split.split:
; CHECK-NEXT: br label %outer_loop
; CHECK: outer_loop:
; CHECK-NEXT: br label %outer_loop.split.us
; CHECK: outer_loop.split.us:
; CHECK-NEXT: br label %loop.us
; CHECK: loop.us:
; CHECK-NEXT: %iv.us = phi i32 [ 0, %outer_loop.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 %outer_backedge.split.us
; CHECK: outer_backedge.split.us:
; CHECK-NEXT: br label %outer_backedge
; CHECK: outer_loop.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: outer_backedge:
; CHECK-NEXT: br label %exit
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %outer_loop
outer_loop:
br label %loop
loop:
%iv = phi i32 [ 0, %outer_loop ], [ %iv.next, %loop ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
%iv.next = add i32 %iv, 1
%loop.cond = icmp slt i32 %iv.next, %N
br i1 %loop.cond, label %loop, label %outer_backedge
outer_backedge:
br i1 %arg, label %outer_loop, label %exit
exit:
ret void
}
define void @test_sibling_loops(i1 %cond1, i1 %cond2, i32 %N) {
; CHECK-LABEL: @test_sibling_loops(
; 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: 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-NEXT: unreachable
;
entry:
br label %loop1
loop1:
%iv1 = phi i32 [ 0, %entry ], [ %iv1.next, %loop1 ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
%iv1.next = add i32 %iv1, 1
%loop1.cond = icmp slt i32 %iv1.next, %N
br i1 %loop1.cond, label %loop1, label %between
between:
br label %loop2
loop2:
%iv2 = phi i32 [ 0, %between ], [ %iv2.next, %loop2 ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ]
%iv2.next = add i32 %iv2, 1
%loop2.cond = icmp slt i32 %iv2.next, %N
br i1 %loop2.cond, label %loop2, label %exit
exit:
ret void
}
; 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 {
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
%iv.next = add i32 %iv, 1
invoke void @may_throw(i32 %iv) to label %loop unwind label %exit
exit:
%cp = cleanuppad within none []
cleanupret from %cp unwind to caller
}
declare void @may_throw(i32 %i)
declare i32 @__CxxFrameHandler3(...)
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