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[SCEV] Allow adds of constants in tryToReuseLCSSAPhi. #150693

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Merged
merged 2 commits into from
Jul 31, 2025
Merged

[SCEV] Allow adds of constants in tryToReuseLCSSAPhi. #150693

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52a4a5f
[SCEV] Allow adds of constants in tryToReuseLCSSAPhi.
fhahn Jul 25, 2025
f0eb073
!fixup Diff -> Op.
fhahn Jul 31, 2025
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3 changes: 2 additions & 1 deletion llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1249,7 +1249,8 @@ Value *SCEVExpander::tryToReuseLCSSAPhi(const SCEVAddRecExpr *S) {
// offset, if the offset is simpler.
const SCEV *Diff = SE.getMinusSCEV(S, ExitSCEV);
const SCEV *Op = Diff;
match(Diff, m_scev_Mul(m_scev_AllOnes(), m_SCEV(Op)));
match(Op, m_scev_Add(m_SCEVConstant(), m_SCEV(Op)));
match(Op, m_scev_Mul(m_scev_AllOnes(), m_SCEV(Op)));
match(Op, m_scev_PtrToInt(m_SCEV(Op)));
if (!isa<SCEVConstant, SCEVUnknown>(Op))
continue;
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5 changes: 2 additions & 3 deletions llvm/test/Transforms/LoopIdiom/reuse-lcssa-phi-scev-expansion.ll
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Expand Up @@ -33,11 +33,10 @@ define void @scev_expand_ptrtoint(i8 %x, ptr %start) {
; CHECK: [[LOOP_3_PREHEADER]]:
; CHECK-NEXT: [[INDVAR_LCSSA:%.*]] = phi i64 [ [[INDVAR]], %[[LOOP_2_HEADER]] ], [ [[INDVAR]], %[[LOOP_2_HEADER]] ]
; CHECK-NEXT: [[PTR_IV_2_LCSSA:%.*]] = phi ptr [ [[PTR_IV_2]], %[[LOOP_2_HEADER]] ], [ [[PTR_IV_2]], %[[LOOP_2_HEADER]] ]
; CHECK-NEXT: [[TMP0:%.*]] = sub i64 0, [[START1]]
; CHECK-NEXT: [[TMP0:%.*]] = sub i64 1, [[START1]]
; CHECK-NEXT: [[TMP1:%.*]] = ptrtoint ptr [[PTR_IV_1_LCSSA]] to i64
; CHECK-NEXT: [[TMP2:%.*]] = add i64 [[TMP1]], [[TMP0]]
; CHECK-NEXT: [[TMP3:%.*]] = add i64 [[TMP2]], 1
; CHECK-NEXT: [[TMP4:%.*]] = add i64 [[CMP_EXT]], [[TMP3]]
; CHECK-NEXT: [[TMP4:%.*]] = add i64 [[CMP_EXT]], [[TMP2]]
; CHECK-NEXT: [[TMP5:%.*]] = add i64 [[INDVAR_LCSSA]], [[TMP4]]
; CHECK-NEXT: [[SCEVGEP:%.*]] = getelementptr i8, ptr [[START]], i64 [[TMP5]]
; CHECK-NEXT: [[STRLEN:%.*]] = call i64 @strlen(ptr [[SCEVGEP]])
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12 changes: 4 additions & 8 deletions llvm/test/Transforms/LoopVectorize/reuse-lcssa-phi-scev-expansion.ll
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Expand Up @@ -389,22 +389,18 @@ define void @scev_exp_reuse_const_add(ptr %dst, ptr %src) {
; CHECK-SAME: ptr [[DST:%.*]], ptr [[SRC:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: [[SRC2:%.*]] = ptrtoint ptr [[SRC]] to i64
; CHECK-NEXT: [[DST1:%.*]] = ptrtoint ptr [[DST]] to i64
; CHECK-NEXT: br label %[[LOOP_1:.*]]
; CHECK: [[LOOP_1]]:
; CHECK-NEXT: [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], %[[LOOP_1]] ], [ 0, %[[ENTRY]] ]
; CHECK-NEXT: [[PTR_IV_1:%.*]] = phi ptr [ [[DST]], %[[ENTRY]] ], [ [[PTR_IV_1_NEXT:%.*]], %[[LOOP_1]] ]
; CHECK-NEXT: [[PTR_IV_1_NEXT]] = getelementptr i8, ptr [[PTR_IV_1]], i64 2
; CHECK-NEXT: [[C:%.*]] = call i1 @cond()
; CHECK-NEXT: [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
; CHECK-NEXT: br i1 [[C]], label %[[LOOP_2_PH:.*]], label %[[LOOP_1]]
; CHECK: [[LOOP_2_PH]]:
; CHECK-NEXT: [[INDVAR_LCSSA:%.*]] = phi i64 [ [[INDVAR]], %[[LOOP_1]] ]
; CHECK-NEXT: [[PTR_IV_1_NEXT_LCSSA:%.*]] = phi ptr [ [[PTR_IV_1_NEXT]], %[[LOOP_1]] ]
; CHECK-NEXT: br i1 false, label %[[SCALAR_PH:.*]], label %[[VECTOR_MEMCHECK:.*]]
; CHECK: [[VECTOR_MEMCHECK]]:
; CHECK-NEXT: [[TMP0:%.*]] = sub i64 [[DST1]], [[SRC2]]
; CHECK-NEXT: [[TMP1:%.*]] = shl i64 [[INDVAR_LCSSA]], 1
; CHECK-NEXT: [[TMP0:%.*]] = sub i64 -2, [[SRC2]]
; CHECK-NEXT: [[TMP1:%.*]] = ptrtoint ptr [[PTR_IV_1_NEXT_LCSSA]] to i64
; CHECK-NEXT: [[TMP2:%.*]] = add i64 [[TMP1]], [[TMP0]]
; CHECK-NEXT: [[DIFF_CHECK:%.*]] = icmp ult i64 [[TMP2]], 4
; CHECK-NEXT: br i1 [[DIFF_CHECK]], label %[[SCALAR_PH]], label %[[VECTOR_PH:.*]]
Expand All @@ -426,11 +422,11 @@ define void @scev_exp_reuse_const_add(ptr %dst, ptr %src) {
; CHECK-NEXT: br label %[[SCALAR_PH]]
; CHECK: [[SCALAR_PH]]:
; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ 40, %[[MIDDLE_BLOCK]] ], [ 0, %[[LOOP_2_PH]] ], [ 0, %[[VECTOR_MEMCHECK]] ]
; CHECK-NEXT: [[BC_RESUME_VAL3:%.*]] = phi ptr [ [[TMP3]], %[[MIDDLE_BLOCK]] ], [ [[PTR_IV_1_NEXT_LCSSA]], %[[LOOP_2_PH]] ], [ [[PTR_IV_1_NEXT_LCSSA]], %[[VECTOR_MEMCHECK]] ]
; CHECK-NEXT: [[BC_RESUME_VAL2:%.*]] = phi ptr [ [[TMP3]], %[[MIDDLE_BLOCK]] ], [ [[PTR_IV_1_NEXT_LCSSA]], %[[LOOP_2_PH]] ], [ [[PTR_IV_1_NEXT_LCSSA]], %[[VECTOR_MEMCHECK]] ]
; CHECK-NEXT: br label %[[LOOP_2:.*]]
; CHECK: [[LOOP_2]]:
; CHECK-NEXT: [[IV_1:%.*]] = phi i64 [ [[BC_RESUME_VAL]], %[[SCALAR_PH]] ], [ [[IV_2_NEXT:%.*]], %[[LOOP_2]] ]
; CHECK-NEXT: [[PTR_IV_2:%.*]] = phi ptr [ [[BC_RESUME_VAL3]], %[[SCALAR_PH]] ], [ [[PTR_IV_2_NEXT:%.*]], %[[LOOP_2]] ]
; CHECK-NEXT: [[PTR_IV_2:%.*]] = phi ptr [ [[BC_RESUME_VAL2]], %[[SCALAR_PH]] ], [ [[PTR_IV_2_NEXT:%.*]], %[[LOOP_2]] ]
; CHECK-NEXT: [[IV_2_NEXT]] = add i64 [[IV_1]], 1
; CHECK-NEXT: [[GEP_SRC_1:%.*]] = getelementptr i16, ptr [[SRC]], i64 [[IV_2_NEXT]]
; CHECK-NEXT: [[L:%.*]] = load i16, ptr [[GEP_SRC_1]], align 2
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