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llvm-project/llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll
Florian Hahn f78150d2d4
Reapply "[SCEV] Fold (C1 * A /u C2) -> A /u (C2 /u C1), if C2 > C1." (#158328) 
This reverts commit fd58f235f8c5bd40d98acfd8e7fb11d41de301c7.

The recommit contains an extra check to make sure that D is a multiple of
C2, if C2 > C1. This fixes the issue causing the revert fd58f235f8c. Tests
have been added in 6a726e9a4d3d0.

Original message:
If C2 >u C1 and C1 >u 1, fold to A /u (C2 /u C1).

Depends on https://github.com/llvm/llvm-project/pull/157555.

Alive2 Proof: https://alive2.llvm.org/ce/z/BWvQYN

PR: https://github.com/llvm/llvm-project/pull/157656
2025-09-17 14:28:30 +01:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -loop-reduce %s | FileCheck %s
; REQUIRES: x86-registered-target
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i64 @test_duplicated_phis(i64 noundef %N) {
; CHECK-LABEL: define i64 @test_duplicated_phis(
; CHECK-SAME: i64 noundef [[N:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[MUL:%.*]] = shl i64 [[N]], 1
; CHECK-NEXT: [[CMP6_NOT:%.*]] = icmp eq i64 [[MUL]], 0
; CHECK-NEXT: br i1 [[CMP6_NOT]], label %[[FOR_END:.*]], label %[[FOR_BODY_PREHEADER:.*]]
; CHECK: [[FOR_BODY_PREHEADER]]:
; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i64 [[MUL]], 4
; CHECK-NEXT: br i1 [[TMP0]], label %[[FOR_END_LOOPEXIT_UNR_LCSSA:.*]], label %[[FOR_BODY_PREHEADER_NEW:.*]]
; CHECK: [[FOR_BODY_PREHEADER_NEW]]:
; CHECK-NEXT: [[UNROLL_ITER:%.*]] = and i64 [[MUL]], -4
; CHECK-NEXT: [[TMP4:%.*]] = add i64 [[UNROLL_ITER]], -4
; CHECK-NEXT: [[TMP3:%.*]] = lshr i64 [[TMP4]], 1
; CHECK-NEXT: [[LSR_IV_NEXT:%.*]] = sub i64 -3, [[TMP3]]
; CHECK-NEXT: br label %[[FOR_BODY:.*]]
; CHECK: [[FOR_BODY]]:
; CHECK-NEXT: [[I_07:%.*]] = phi i64 [ 0, %[[FOR_BODY_PREHEADER_NEW]] ], [ [[INC_3:%.*]], %[[FOR_BODY]] ]
; CHECK-NEXT: [[INC_3]] = add i64 [[I_07]], 4
; CHECK-NEXT: [[NITER_NCMP_3_NOT:%.*]] = icmp eq i64 [[UNROLL_ITER]], [[INC_3]]
; CHECK-NEXT: br i1 [[NITER_NCMP_3_NOT]], label %[[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT:.*]], label %[[FOR_BODY]]
; CHECK: [[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]]:
; CHECK-NEXT: [[TMP1:%.*]] = add i64 [[LSR_IV_NEXT]], 1
; CHECK-NEXT: br label %[[FOR_END_LOOPEXIT_UNR_LCSSA]]
; CHECK: [[FOR_END_LOOPEXIT_UNR_LCSSA]]:
; CHECK-NEXT: [[RES_1_LCSSA_PH:%.*]] = phi i64 [ undef, %[[FOR_BODY_PREHEADER]] ], [ [[TMP1]], %[[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]] ]
; CHECK-NEXT: [[RES_09_UNR:%.*]] = phi i64 [ -1, %[[FOR_BODY_PREHEADER]] ], [ [[LSR_IV_NEXT]], %[[FOR_END_LOOPEXIT_UNR_LCSSA_LOOPEXIT]] ]
; CHECK-NEXT: [[TMP2:%.*]] = and i64 [[N]], 1
; CHECK-NEXT: [[LCMP_MOD_NOT:%.*]] = icmp eq i64 [[TMP2]], 0
; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[LCMP_MOD_NOT]], i64 [[RES_1_LCSSA_PH]], i64 [[RES_09_UNR]]
; CHECK-NEXT: br label %[[FOR_END]]
; CHECK: [[FOR_END]]:
; CHECK-NEXT: [[RES_0_LCSSA:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[SPEC_SELECT]], %[[FOR_END_LOOPEXIT_UNR_LCSSA]] ]
; CHECK-NEXT: ret i64 [[RES_0_LCSSA]]
;
entry:
%mul = shl i64 %N, 1
%cmp6.not = icmp eq i64 %mul, 0
br i1 %cmp6.not, label %for.end, label %for.body.preheader
for.body.preheader:
%0 = icmp ult i64 %mul, 4
br i1 %0, label %for.end.loopexit.unr-lcssa, label %for.body.preheader.new
for.body.preheader.new:
%unroll_iter = and i64 %mul, -4
br label %for.body
for.body:
%res.09 = phi i64 [ 0, %for.body.preheader.new ], [ %res.1.3, %for.body ]
%i.07 = phi i64 [ 0, %for.body.preheader.new ], [ %inc.3, %for.body ]
%niter = phi i64 [ 0, %for.body.preheader.new ], [ %niter.next.3, %for.body ]
%res.1.1 = add i64 %res.09, -1
%inc.1 = or disjoint i64 %i.07, 2
%res.1.2 = add i64 %inc.1, %res.1.1
%reass.sub = sub i64 %res.1.2, %i.07
%res.1.3 = add i64 %reass.sub, -3
%inc.3 = add nuw i64 %i.07, 4
%niter.next.3 = add i64 %niter, 4
%niter.ncmp.3.not = icmp eq i64 %niter.next.3, %unroll_iter
br i1 %niter.ncmp.3.not, label %for.end.loopexit.unr-lcssa.loopexit, label %for.body
for.end.loopexit.unr-lcssa.loopexit:
%1 = add i64 %reass.sub, -4
br label %for.end.loopexit.unr-lcssa
for.end.loopexit.unr-lcssa:
%res.1.lcssa.ph = phi i64 [ undef, %for.body.preheader ], [ %res.1.3, %for.end.loopexit.unr-lcssa.loopexit ]
%res.09.unr = phi i64 [ -1, %for.body.preheader ], [ %1, %for.end.loopexit.unr-lcssa.loopexit ]
%2 = and i64 %N, 1
%lcmp.mod.not = icmp eq i64 %2, 0
%spec.select = select i1 %lcmp.mod.not, i64 %res.1.lcssa.ph, i64 %res.09.unr
br label %for.end
for.end:
%res.0.lcssa = phi i64 [ 0, %entry ], [ %spec.select, %for.end.loopexit.unr-lcssa ]
ret i64 %res.0.lcssa
}
define i64 @duplicated_phis_compare_uses_mul_udiv(i64 %x) {
; CHECK-LABEL: define i64 @duplicated_phis_compare_uses_mul_udiv(
; CHECK-SAME: i64 [[X:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[MUL_2:%.*]] = shl i64 [[X]], 1
; CHECK-NEXT: [[DIV_16:%.*]] = lshr i64 [[MUL_2]], 4
; CHECK-NEXT: [[MASKED:%.*]] = and i64 [[DIV_16]], 1152921504606846974
; CHECK-NEXT: br label %[[LOOP:.*]]
; CHECK: [[LOOP]]:
; CHECK-NEXT: [[IV_1:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[IV_1_NEXT:%.*]], %[[LOOP]] ]
; CHECK-NEXT: call void @clobber()
; CHECK-NEXT: [[IV_1_NEXT]] = add i64 [[IV_1]], 2
; CHECK-NEXT: [[EC:%.*]] = icmp eq i64 [[MASKED]], [[IV_1_NEXT]]
; CHECK-NEXT: br i1 [[EC]], label %[[EXIT:.*]], label %[[LOOP]]
; CHECK: [[EXIT]]:
; CHECK-NEXT: ret i64 [[IV_1_NEXT]]
;
entry:
%mul.2 = shl i64 %x, 1
%div.16 = lshr exact i64 %mul.2, 4
%masked = and i64 %div.16, 1152921504606846974
br label %loop
loop:
%iv.1 = phi i64 [ 0, %entry ], [ %iv.1.next, %loop ]
%iv.2 = phi i64 [ 0, %entry ], [ %iv.2.next, %loop ]
call void @clobber()
%iv.1.next = add i64 %iv.1, 2
%iv.2.next = add i64 %iv.2, 2
%ec = icmp eq i64 %iv.2.next, %masked
br i1 %ec, label %exit, label %loop
exit:
ret i64 %iv.1.next
}
declare void @clobber()
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