From e89632a96870e48f7dc26d19c0546a3bb9f747cf Mon Sep 17 00:00:00 2001 From: Florian Hahn Date: Mon, 22 Sep 2025 11:46:30 +0100 Subject: [PATCH] [SCEV] Collect guard info for ICMP NE w/o constants. When collecting information from loop guards, use UMax(1, %b - %a) for ICMP NE %a, %b, if neither are constant. This improves results in some cases, and will be even more useful together with * https://github.com/llvm/llvm-project/pull/160012 * https://github.com/llvm/llvm-project/pull/159942 https://alive2.llvm.org/ce/z/YyBvoT --- llvm/lib/Analysis/ScalarEvolution.cpp | 10 ++++++++++ llvm/test/Analysis/ScalarEvolution/ptrtoint.ll | 10 +++++----- .../Transforms/IndVarSimplify/pointer-loop-guards.ll | 2 +- llvm/test/Transforms/LoopUnroll/scevunroll.ll | 3 +-- 4 files changed, 17 insertions(+), 8 deletions(-) diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 63e1b1462d007..7df867cd4de44 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -15873,6 +15873,16 @@ void ScalarEvolution::LoopGuards::collectFromBlock( const SCEV *OneAlignedUp = DividesBy ? GetNextSCEVDividesByDivisor(One, DividesBy) : One; To = SE.getUMaxExpr(FromRewritten, OneAlignedUp); + } else { + if (LHS->getType()->isPointerTy()) { + LHS = SE.getLosslessPtrToIntExpr(LHS); + RHS = SE.getLosslessPtrToIntExpr(RHS); + if (isa(LHS) || isa(RHS)) + break; + } + From = SE.getMinusSCEV(RHS, LHS); + FromRewritten = From; + To = SE.getUMaxExpr(FromRewritten, SE.getOne(From->getType())); } break; default: diff --git a/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll b/llvm/test/Analysis/ScalarEvolution/ptrtoint.ll index e784d25385980..6db2f21352c49 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}<%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}<%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}<%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}<%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}<%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: <> LoopDispositions: { %bb6: Variant } ; X32-NEXT: %i9 = ptrtoint ptr %i7 to i64 -; X32-NEXT: --> {(zext i32 (ptrtoint ptr %arg to i32) to i64),+,1}<%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}<%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}<%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}<%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}<%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 ; 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]]