Author: Reid Kleckner Date: 2025-09-12T09:42:19-07:00 New Revision: 67678c86a48bcae33bd28045fc0776436612319a
URL: https://github.com/llvm/llvm-project/commit/67678c86a48bcae33bd28045fc0776436612319a DIFF: https://github.com/llvm/llvm-project/commit/67678c86a48bcae33bd28045fc0776436612319a.diff LOG: Revert "[SCEV] Fold (C1 * A /u C2) -> A /u (C2 /u C1), if C2 > C1. (#157656)" This reverts commit 70012fda6312ba87bc0bf9009402e0869a816d1f. Added: Modified: llvm/lib/Analysis/ScalarEvolution.cpp llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll Removed: ################################################################################ diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 5bcafd96f1aa5..a1703a270952e 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -3217,26 +3217,18 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops, } // Try to fold (C1 * D /u C2) -> C1/C2 * D, if C1 and C2 are powers-of-2, - // D is a multiple of C2, and C1 is a multiple of C2. If C2 is a multiple - // of C1, fold to (D /u (C2 /u C1)). + // D is a multiple of C2, and C1 is a multiple of C2. const SCEV *D; APInt C1V = LHSC->getAPInt(); - // (C1 * D /u C2) == -1 * -C1 * D /u C2 when C1 != INT_MIN. Don't treat -1 - // as -1 * 1, as it won't enable additional folds. - if (C1V.isNegative() && !C1V.isMinSignedValue() && !C1V.isAllOnes()) + // (C1 * D /u C2) == -1 * -C1 * D /u C2 when C1 != INT_MIN. + if (C1V.isNegative() && !C1V.isMinSignedValue()) C1V = C1V.abs(); const SCEVConstant *C2; if (C1V.isPowerOf2() && match(Ops[1], m_scev_UDiv(m_SCEV(D), m_SCEVConstant(C2))) && - C2->getAPInt().isPowerOf2() && + C2->getAPInt().isPowerOf2() && C1V.uge(C2->getAPInt()) && C1V.logBase2() <= getMinTrailingZeros(D)) { - const SCEV *NewMul; - if (C1V.uge(C2->getAPInt())) { - NewMul = getMulExpr(getUDivExpr(getConstant(C1V), C2), D); - } else { - assert(C1V.ugt(1) && "C1 <= 1 should have been folded earlier"); - NewMul = getUDivExpr(D, getUDivExpr(C2, getConstant(C1V))); - } + const SCEV *NewMul = getMulExpr(getUDivExpr(getConstant(C1V), C2), D); return C1V == LHSC->getAPInt() ? NewMul : getNegativeSCEV(NewMul); } } diff --git a/llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll b/llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll index 1d34706baadeb..8dd8ec47e7090 100644 --- a/llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll +++ b/llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll @@ -21,7 +21,7 @@ define void @udiv4_and_udiv2(i1 %c, ptr %A) { ; CHECK-NEXT: %gep.8 = getelementptr i8, ptr %A, i64 %iv ; CHECK-NEXT: --> {(((zext i32 %start to i64) /u 4) + %A),+,1}<%loop> U: full-set S: full-set Exits: (((zext i32 %start to i64) /u 2) + %A) LoopDispositions: { %loop: Computable } ; CHECK-NEXT: %gep.16 = getelementptr i16, ptr %A, i64 %iv -; CHECK-NEXT: --> {(((zext i32 %start to i64) /u 2) + %A),+,2}<%loop> U: full-set S: full-set Exits: ((zext i32 %start to i64) + %A) LoopDispositions: { %loop: Computable } +; CHECK-NEXT: --> {((2 * ((zext i32 %start to i64) /u 4))<nuw><nsw> + %A),+,2}<%loop> U: full-set S: full-set Exits: ((zext i32 %start to i64) + %A) LoopDispositions: { %loop: Computable } ; CHECK-NEXT: %gep.32 = getelementptr i32, ptr %A, i64 %iv ; CHECK-NEXT: --> {((zext i32 %start to i64) + %A),+,4}<%loop> U: full-set S: full-set Exits: ((2 * (zext i32 %start to i64))<nuw><nsw> + %A) LoopDispositions: { %loop: Computable } ; CHECK-NEXT: %gep.40 = getelementptr <{ i32, i8 }>, ptr %A, i64 %iv diff --git a/llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll b/llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll index c59f7d9c2a41a..cee8c8abdb450 100644 --- a/llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll +++ b/llvm/test/Transforms/LoopStrengthReduce/duplicated-phis.ll @@ -18,7 +18,8 @@ define i64 @test_duplicated_phis(i64 noundef %N) { ; 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: [[TMP5:%.*]] = lshr i64 [[TMP4]], 2 +; CHECK-NEXT: [[TMP3:%.*]] = shl nuw nsw i64 [[TMP5]], 1 ; CHECK-NEXT: [[LSR_IV_NEXT:%.*]] = sub i64 -3, [[TMP3]] ; CHECK-NEXT: br label %[[FOR_BODY:.*]] ; CHECK: [[FOR_BODY]]: _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
