[SCEV] Preserve divisor info when adding guard info for ICMP_NE via Sub. #163250
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llvmbot added llvm:analysis 
| @llvm/pr-subscribers-llvm-analysis @llvm/pr-subscribers-llvm-transforms Author: Florian Hahn (fhahn) ChangesFollow-up to #160500 to Full diff: https://github.com/llvm/llvm-project/pull/163250.diff 5 Files Affected:
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 00c3dbbf3e800..3d99f4cadf3c2 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -15827,6 +15827,22 @@ void ScalarEvolution::LoopGuards::collectFromBlock( const SCEV *OneAlignedUp = GetNextSCEVDividesByDivisor(One, DividesBy); To = SE.getUMaxExpr(FromRewritten, OneAlignedUp); + } else { + if (LHS->getType()->isPointerTy()) { + LHS = SE.getLosslessPtrToIntExpr(LHS); + RHS = SE.getLosslessPtrToIntExpr(RHS); + if (isa<SCEVCouldNotCompute>(LHS) || isa<SCEVCouldNotCompute>(RHS)) + break; + } + auto AddSubRewrite = [&](const SCEV *A, const SCEV *B) { + const SCEV *Sub = SE.getMinusSCEV(A, B); + const SCEV *OneAlignedUp = GetNextSCEVDividesByDivisor( + SE.getOne(From->getType()), SE.getConstantMultiple(Sub)); + AddRewrite(Sub, Sub, SE.getUMaxExpr(Sub, OneAlignedUp)); + }; + AddSubRewrite(LHS, RHS); + AddSubRewrite(RHS, LHS); + continue; } break; default: diff --git a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll index 4024c986dd11d..d5a2181e9bc5e 100644 --- a/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll +++ b/llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll @@ -1431,7 +1431,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_load(ptr %a, ptr %b, pt ; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count. ; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) -; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951 +; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950 ; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) ; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) @@ -1470,7 +1470,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_arguments(ptr align 8 % ; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count. ; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8) -; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951 +; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950 ; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8) ; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8) @@ -1511,7 +1511,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_1(ptr %a, ptr %b, pt ; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count. ; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) -; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951 +; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950 ; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) ; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) @@ -1556,7 +1556,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_2(ptr %a, ptr %b, pt ; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count. ; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) -; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693951 +; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i64 2305843009213693950 ; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) ; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE*** ; CHECK-NEXT: symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8) diff --git a/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll b/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll index acac2c98ad174..0c1f37bf58601 100644 --- a/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll +++ b/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll @@ -382,7 +382,7 @@ define void @pr46786_c26_char(ptr %arg, ptr %arg1, ptr %arg2) { ; X64-NEXT: %i9 = ptrtoint ptr %i7 to i64 ; X64-NEXT: --> {(ptrtoint ptr %arg to i64),+,1}<nuw><%bb6> U: full-set S: full-set Exits: (-1 + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i10 = sub i64 %i9, %i4 -; X64-NEXT: --> {0,+,1}<nuw><%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } +; X64-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,-1) S: [0,-1) Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i11 = getelementptr inbounds i8, ptr %arg2, i64 %i10 ; X64-NEXT: --> {%arg2,+,1}<nw><%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64) + %arg2) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i12 = load i8, ptr %i11, align 1 @@ -393,7 +393,7 @@ define void @pr46786_c26_char(ptr %arg, ptr %arg1, ptr %arg2) { ; X64-NEXT: --> {(1 + %arg),+,1}<nuw><%bb6> U: full-set S: full-set Exits: ((-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64) + %arg) LoopDispositions: { %bb6: Computable } ; X64-NEXT: Determining loop execution counts for: @pr46786_c26_char ; X64-NEXT: Loop %bb6: backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) -; X64-NEXT: Loop %bb6: constant max backedge-taken count is i64 -1 +; X64-NEXT: Loop %bb6: constant max backedge-taken count is i64 -2 ; X64-NEXT: Loop %bb6: symbolic max backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) ; X64-NEXT: Loop %bb6: Trip multiple is 1 ; @@ -406,9 +406,9 @@ define void @pr46786_c26_char(ptr %arg, ptr %arg1, ptr %arg2) { ; X32-NEXT: %i8 = load i8, ptr %i7, align 1 ; X32-NEXT: --> %i8 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb6: Variant } ; X32-NEXT: %i9 = ptrtoint ptr %i7 to i64 -; X32-NEXT: --> {(zext i32 (ptrtoint ptr %arg to i32) to i64),+,1}<nuw><%bb6> U: [0,8589934591) S: [0,8589934591) Exits: ((zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) + (zext i32 (ptrtoint ptr %arg to i32) to i64)) LoopDispositions: { %bb6: Computable } +; X32-NEXT: --> {(zext i32 (ptrtoint ptr %arg to i32) to i64),+,1}<nuw><%bb6> U: [0,8589934590) S: [0,8589934590) Exits: ((zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) + (zext i32 (ptrtoint ptr %arg to i32) to i64)) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i10 = sub i64 %i9, %i4 -; X32-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,4294967296) S: [0,4294967296) Exits: (zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) LoopDispositions: { %bb6: Computable } +; X32-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,4294967295) S: [0,4294967295) Exits: (zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i11 = getelementptr inbounds i8, ptr %arg2, i64 %i10 ; X32-NEXT: --> {%arg2,+,1}<%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32) + %arg2) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i12 = load i8, ptr %i11, align 1 @@ -419,7 +419,7 @@ define void @pr46786_c26_char(ptr %arg, ptr %arg1, ptr %arg2) { ; X32-NEXT: --> {(1 + %arg),+,1}<nuw><%bb6> U: full-set S: full-set Exits: ((-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32) + %arg) LoopDispositions: { %bb6: Computable } ; X32-NEXT: Determining loop execution counts for: @pr46786_c26_char ; X32-NEXT: Loop %bb6: backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) -; X32-NEXT: Loop %bb6: constant max backedge-taken count is i32 -1 +; X32-NEXT: Loop %bb6: constant max backedge-taken count is i32 -2 ; X32-NEXT: Loop %bb6: symbolic max backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) ; X32-NEXT: Loop %bb6: Trip multiple is 1 ; @@ -459,7 +459,7 @@ define void @pr46786_c26_char_cmp_ops_swapped(ptr %arg, ptr %arg1, ptr %arg2) { ; X64-NEXT: %i9 = ptrtoint ptr %i7 to i64 ; X64-NEXT: --> {(ptrtoint ptr %arg to i64),+,1}<nuw><%bb6> U: full-set S: full-set Exits: (-1 + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i10 = sub i64 %i9, %i4 -; X64-NEXT: --> {0,+,1}<nuw><%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } +; X64-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,-1) S: [0,-1) Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i11 = getelementptr inbounds i8, ptr %arg2, i64 %i10 ; X64-NEXT: --> {%arg2,+,1}<nw><%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64) + %arg2) LoopDispositions: { %bb6: Computable } ; X64-NEXT: %i12 = load i8, ptr %i11, align 1 @@ -470,7 +470,7 @@ define void @pr46786_c26_char_cmp_ops_swapped(ptr %arg, ptr %arg1, ptr %arg2) { ; X64-NEXT: --> {(1 + %arg),+,1}<nuw><%bb6> U: full-set S: full-set Exits: ((-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64) + %arg) LoopDispositions: { %bb6: Computable } ; X64-NEXT: Determining loop execution counts for: @pr46786_c26_char_cmp_ops_swapped ; X64-NEXT: Loop %bb6: backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) -; X64-NEXT: Loop %bb6: constant max backedge-taken count is i64 -1 +; X64-NEXT: Loop %bb6: constant max backedge-taken count is i64 -2 ; X64-NEXT: Loop %bb6: symbolic max backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i64)) + (ptrtoint ptr %arg1 to i64)) ; X64-NEXT: Loop %bb6: Trip multiple is 1 ; @@ -483,9 +483,9 @@ define void @pr46786_c26_char_cmp_ops_swapped(ptr %arg, ptr %arg1, ptr %arg2) { ; X32-NEXT: %i8 = load i8, ptr %i7, align 1 ; X32-NEXT: --> %i8 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb6: Variant } ; X32-NEXT: %i9 = ptrtoint ptr %i7 to i64 -; X32-NEXT: --> {(zext i32 (ptrtoint ptr %arg to i32) to i64),+,1}<nuw><%bb6> U: [0,8589934591) S: [0,8589934591) Exits: ((zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) + (zext i32 (ptrtoint ptr %arg to i32) to i64)) LoopDispositions: { %bb6: Computable } +; X32-NEXT: --> {(zext i32 (ptrtoint ptr %arg to i32) to i64),+,1}<nuw><%bb6> U: [0,8589934590) S: [0,8589934590) Exits: ((zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) + (zext i32 (ptrtoint ptr %arg to i32) to i64)) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i10 = sub i64 %i9, %i4 -; X32-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,4294967296) S: [0,4294967296) Exits: (zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) LoopDispositions: { %bb6: Computable } +; X32-NEXT: --> {0,+,1}<nuw><%bb6> U: [0,4294967295) S: [0,4294967295) Exits: (zext i32 (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) to i64) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i11 = getelementptr inbounds i8, ptr %arg2, i64 %i10 ; X32-NEXT: --> {%arg2,+,1}<%bb6> U: full-set S: full-set Exits: (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32) + %arg2) LoopDispositions: { %bb6: Computable } ; X32-NEXT: %i12 = load i8, ptr %i11, align 1 @@ -496,7 +496,7 @@ define void @pr46786_c26_char_cmp_ops_swapped(ptr %arg, ptr %arg1, ptr %arg2) { ; X32-NEXT: --> {(1 + %arg),+,1}<nuw><%bb6> U: full-set S: full-set Exits: ((-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32) + %arg) LoopDispositions: { %bb6: Computable } ; X32-NEXT: Determining loop execution counts for: @pr46786_c26_char_cmp_ops_swapped ; X32-NEXT: Loop %bb6: backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) -; X32-NEXT: Loop %bb6: constant max backedge-taken count is i32 -1 +; X32-NEXT: Loop %bb6: constant max backedge-taken count is i32 -2 ; X32-NEXT: Loop %bb6: symbolic max backedge-taken count is (-1 + (-1 * (ptrtoint ptr %arg to i32)) + (ptrtoint ptr %arg1 to i32)) ; X32-NEXT: Loop %bb6: Trip multiple is 1 ; diff --git a/llvm/test/Transforms/IndVarSimplify/pointer-loop-guards.ll b/llvm/test/Transforms/IndVarSimplify/pointer-loop-guards.ll index 89b132e981899..9371fe24be05d 100644 --- a/llvm/test/Transforms/IndVarSimplify/pointer-loop-guards.ll +++ b/llvm/test/Transforms/IndVarSimplify/pointer-loop-guards.ll @@ -18,7 +18,7 @@ define i64 @test_ptr_compare_guard(ptr %start, ptr %end) { ; CHECK-NEXT: br i1 [[C_1]], label %[[LOOP_LATCH]], label %[[EXIT_LOOPEXIT:.*]] ; CHECK: [[LOOP_LATCH]]: ; CHECK-NEXT: [[PTR_IV_NEXT]] = getelementptr i8, ptr [[PTR_IV]], i64 1 -; CHECK-NEXT: [[I64_IV_NEXT]] = add i64 [[I64_IV]], 1 +; CHECK-NEXT: [[I64_IV_NEXT]] = add nuw i64 [[I64_IV]], 1 ; CHECK-NEXT: [[C_2:%.*]] = icmp eq ptr [[PTR_IV_NEXT]], [[END]] ; CHECK-NEXT: br i1 [[C_2]], label %[[EXIT_LOOPEXIT]], label %[[LOOP_HEADER]] ; CHECK: [[EXIT_LOOPEXIT]]: diff --git a/llvm/test/Transforms/LoopUnroll/scevunroll.ll b/llvm/test/Transforms/LoopUnroll/scevunroll.ll index fa55eab062198..bc63f79296a30 100644 --- a/llvm/test/Transforms/LoopUnroll/scevunroll.ll +++ b/llvm/test/Transforms/LoopUnroll/scevunroll.ll @@ -465,8 +465,7 @@ define void @peel_int_eq_condition(i32 %start) { ; CHECK-NEXT: br label [[LOOP:%.*]] ; CHECK: loop: ; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[IV_NEXT_PEEL]], [[ENTRY_PEEL_NEWPH]] ], [ [[IV_NEXT:%.*]], [[LOOP_LATCH:%.*]] ] -; CHECK-NEXT: [[C_0:%.*]] = icmp eq i32 [[IV]], [[START]] -; CHECK-NEXT: br i1 [[C_0]], label [[IF_THEN:%.*]], label [[LOOP_LATCH]] +; CHECK-NEXT: br i1 false, label [[IF_THEN:%.*]], label [[LOOP_LATCH]] ; CHECK: if.then: ; CHECK-NEXT: call void @fn(i32 [[IV]]) ; CHECK-NEXT: br label [[LOOP_LATCH]] |
This was referenced Oct 13, 2025
| There's no impact on llvm-opt-benchmarks (dtcxzyw/llvm-opt-benchmark#2925) over #160500 (dtcxzyw/llvm-opt-benchmark#2859), but it will help together with #163260 & #159942 |
Follow-up to llvm#160500 to preserve divisibiltiy info when creating the UMax.
fhahn force-pushed the scev-guard-ne-preserve-divisor branch from b0ccf0c to 3e424b4 Compare 
| ✅ With the latest revision this PR passed the C/C++ code formatter. |
llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this pull request Oct 20, 2025
…MP_NE via Sub. (#163250) Follow-up to llvm/llvm-project#160500 to preserve divisibiltiy info when creating the UMax. PR: llvm/llvm-project#163250
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Follow-up to #160500 to
preserve divisibiltiy info when creating the UMax.