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llvm-project/llvm/test/Transforms/IndVarSimplify/shift-range-checks.ll
Philip Reames c752bb9203
[IndVars] Strengthen inference of samesign flags (#170363) 
When reviewing another change, I noticed that we were failing to infer
samsign for two cases: 1) an unsigned comparison, and 2) when both
arguments were known negative.

Using CVP and InstCombine as a reference, we need to be careful to not
allow eq/ne comparisons. I'm a bit unclear on the why of that, and for
now am going with the low risk change. I may return to investigate that
in a follow up.

Compile time results look like noise to me, see:
https://llvm-compile-time-tracker.com/compare.php?from=49a978712893fcf9e5f40ac488315d029cf15d3d&to=2ddb263604fd7d538e09dc1f805ebc30eb3ffab0&stat=instructions:u
2025-12-03 16:16:22 +00:00

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7.0 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S < %s -passes=indvars | FileCheck %s
declare i1 @cond()
declare void @exit(i32 %code)
define void @test_01(ptr %p, i32 %shift) {
; CHECK-LABEL: @test_01(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0:![0-9]+]]
; CHECK-NEXT: [[X_SHIFTED:%.*]] = lshr i32 [[X]], [[SHIFT:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: [[LESS_THAN_SHIFTED:%.*]] = icmp samesign ult i32 [[IV]], [[X_SHIFTED]]
; CHECK-NEXT: br i1 [[LESS_THAN_SHIFTED]], label [[GUARDED:%.*]], label [[FAILURE:%.*]]
; CHECK: guarded:
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[NEVER_HAPPENS:%.*]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[LOOP_COND:%.*]] = call i1 @cond()
; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
; CHECK: done:
; CHECK-NEXT: ret void
; CHECK: failure:
; CHECK-NEXT: call void @exit(i32 1)
; CHECK-NEXT: unreachable
; CHECK: never_happens:
; CHECK-NEXT: call void @exit(i32 0)
; CHECK-NEXT: unreachable
;
entry:
%x = load i32, ptr %p, !range !0
%x.shifted = lshr i32 %x, %shift
br label %loop
loop:
%iv = phi i32 [0, %entry], [%iv.next, %backedge]
%less.than.shifted = icmp slt i32 %iv, %x.shifted
br i1 %less.than.shifted, label %guarded, label %failure
guarded:
%less.than.x = icmp slt i32 %iv, %x
br i1 %less.than.x, label %backedge, label %never_happens
backedge:
%iv.next = add nuw nsw i32 %iv, 1
%loop.cond = call i1 @cond()
br i1 %loop.cond, label %loop, label %done
done:
ret void
failure:
call void @exit(i32 1)
unreachable
never_happens:
call void @exit(i32 0)
unreachable
}
define void @test_02(ptr %p, i32 %shift) {
; CHECK-LABEL: @test_02(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
; CHECK-NEXT: [[X_SHIFTED:%.*]] = lshr i32 [[X]], [[SHIFT:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: [[LESS_THAN_SHIFTED:%.*]] = icmp samesign ugt i32 [[X_SHIFTED]], [[IV]]
; CHECK-NEXT: br i1 [[LESS_THAN_SHIFTED]], label [[GUARDED:%.*]], label [[FAILURE:%.*]]
; CHECK: guarded:
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[NEVER_HAPPENS:%.*]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[LOOP_COND:%.*]] = call i1 @cond()
; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
; CHECK: done:
; CHECK-NEXT: ret void
; CHECK: failure:
; CHECK-NEXT: call void @exit(i32 1)
; CHECK-NEXT: unreachable
; CHECK: never_happens:
; CHECK-NEXT: call void @exit(i32 0)
; CHECK-NEXT: unreachable
;
entry:
%x = load i32, ptr %p, !range !0
%x.shifted = lshr i32 %x, %shift
br label %loop
loop:
%iv = phi i32 [0, %entry], [%iv.next, %backedge]
%less.than.shifted = icmp sgt i32 %x.shifted, %iv
br i1 %less.than.shifted, label %guarded, label %failure
guarded:
%less.than.x = icmp sgt i32 %x, %iv
br i1 %less.than.x, label %backedge, label %never_happens
backedge:
%iv.next = add nuw nsw i32 %iv, 1
%loop.cond = call i1 @cond()
br i1 %loop.cond, label %loop, label %done
done:
ret void
failure:
call void @exit(i32 1)
unreachable
never_happens:
call void @exit(i32 0)
unreachable
}
define void @test_03(ptr %p, i32 %shift) {
; CHECK-LABEL: @test_03(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
; CHECK-NEXT: [[X_SHIFTED:%.*]] = lshr i32 [[X]], [[SHIFT:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: [[LESS_THAN_SHIFTED:%.*]] = icmp samesign ult i32 [[IV]], [[X_SHIFTED]]
; CHECK-NEXT: br i1 [[LESS_THAN_SHIFTED]], label [[GUARDED:%.*]], label [[FAILURE:%.*]]
; CHECK: guarded:
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[NEVER_HAPPENS:%.*]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[LOOP_COND:%.*]] = call i1 @cond()
; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
; CHECK: done:
; CHECK-NEXT: ret void
; CHECK: failure:
; CHECK-NEXT: call void @exit(i32 1)
; CHECK-NEXT: unreachable
; CHECK: never_happens:
; CHECK-NEXT: call void @exit(i32 0)
; CHECK-NEXT: unreachable
;
entry:
%x = load i32, ptr %p, !range !0
%x.shifted = lshr i32 %x, %shift
br label %loop
loop:
%iv = phi i32 [0, %entry], [%iv.next, %backedge]
%less.than.shifted = icmp ult i32 %iv, %x.shifted
br i1 %less.than.shifted, label %guarded, label %failure
guarded:
%less.than.x = icmp ult i32 %iv, %x
br i1 %less.than.x, label %backedge, label %never_happens
backedge:
%iv.next = add nuw nsw i32 %iv, 1
%loop.cond = call i1 @cond()
br i1 %loop.cond, label %loop, label %done
done:
ret void
failure:
call void @exit(i32 1)
unreachable
never_happens:
call void @exit(i32 0)
unreachable
}
define void @test_04(ptr %p, i32 %shift) {
; CHECK-LABEL: @test_04(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
; CHECK-NEXT: [[X_SHIFTED:%.*]] = lshr i32 [[X]], [[SHIFT:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: [[LESS_THAN_SHIFTED:%.*]] = icmp samesign ugt i32 [[X_SHIFTED]], [[IV]]
; CHECK-NEXT: br i1 [[LESS_THAN_SHIFTED]], label [[GUARDED:%.*]], label [[FAILURE:%.*]]
; CHECK: guarded:
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[NEVER_HAPPENS:%.*]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[LOOP_COND:%.*]] = call i1 @cond()
; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]]
; CHECK: done:
; CHECK-NEXT: ret void
; CHECK: failure:
; CHECK-NEXT: call void @exit(i32 1)
; CHECK-NEXT: unreachable
; CHECK: never_happens:
; CHECK-NEXT: call void @exit(i32 0)
; CHECK-NEXT: unreachable
;
entry:
%x = load i32, ptr %p, !range !0
%x.shifted = lshr i32 %x, %shift
br label %loop
loop:
%iv = phi i32 [0, %entry], [%iv.next, %backedge]
%less.than.shifted = icmp ugt i32 %x.shifted, %iv
br i1 %less.than.shifted, label %guarded, label %failure
guarded:
%less.than.x = icmp ugt i32 %x, %iv
br i1 %less.than.x, label %backedge, label %never_happens
backedge:
%iv.next = add nuw nsw i32 %iv, 1
%loop.cond = call i1 @cond()
br i1 %loop.cond, label %loop, label %done
done:
ret void
failure:
call void @exit(i32 1)
unreachable
never_happens:
call void @exit(i32 0)
unreachable
}
!0 = !{i32 0, i32 2147483647}
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