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[SCCP] Remove masking operations #142736

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Merged
dtcxzyw merged 4 commits into from
Jun 4, 2025
Merged

[SCCP] Remove masking operations #142736

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b2fd3c7
[SCCP] Remove masking operations
dtcxzyw Jun 2, 2025
39c7b9e
[SCCP] Update tests. NFC.
dtcxzyw Jun 4, 2025
175612e
[SCCP] Move the logic out of `refineInstruction`. NFC.
dtcxzyw Jun 4, 2025
96a2a17
[SCCP] Simplify code. NFC.
dtcxzyw Jun 4, 2025
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19 changes: 17 additions & 2 deletions llvm/lib/Transforms/Utils/SCCPSolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#include "llvm/Analysis/ValueLatticeUtils.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
Expand All @@ -30,6 +31,7 @@
#include <vector>

using namespace llvm;
using namespace PatternMatch;

#define DEBUG_TYPE "sccp"

Expand Down Expand Up @@ -86,7 +88,7 @@ bool SCCPSolver::tryToReplaceWithConstant(Value *V) {
/// Try to use \p Inst's value range from \p Solver to infer the NUW flag.
static bool refineInstruction(SCCPSolver &Solver,
const SmallPtrSetImpl<Value *> &InsertedValues,
Instruction &Inst) {
Instruction &Inst, Statistic &InstRemovedStat) {
bool Changed = false;
auto GetRange = [&Solver, &InsertedValues](Value *Op) {
if (auto *Const = dyn_cast<Constant>(Op))
Expand All @@ -99,6 +101,9 @@ static bool refineInstruction(SCCPSolver &Solver,
Op->getType(), /*UndefAllowed=*/false);
};

Value *X;
const APInt *RHSC;

if (isa<OverflowingBinaryOperator>(Inst)) {
if (Inst.hasNoSignedWrap() && Inst.hasNoUnsignedWrap())
return false;
Expand Down Expand Up @@ -157,6 +162,15 @@ static bool refineInstruction(SCCPSolver &Solver,
GEPNoWrapFlags::noUnsignedWrap());
Changed = true;
}
} else if (match(&Inst, m_And(m_Value(X), m_LowBitMask(RHSC)))) {
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@nikic nikic Jun 4, 2025

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Could try generalizing this away from LowBitMask in a followup. For CVP this reduces compile-time, but for IPSCCP it shouldn't matter.

ConstantRange LRange = GetRange(Inst.getOperand(0));
if (!LRange.getUnsignedMax().ule(*RHSC))
return false;

Inst.replaceAllUsesWith(X);
Inst.eraseFromParent();
++InstRemovedStat;
Changed = true;
}

return Changed;
Expand Down Expand Up @@ -249,7 +263,8 @@ bool SCCPSolver::simplifyInstsInBlock(BasicBlock &BB,
} else if (replaceSignedInst(*this, InsertedValues, Inst)) {
MadeChanges = true;
++InstReplacedStat;
} else if (refineInstruction(*this, InsertedValues, Inst)) {
} else if (refineInstruction(*this, InsertedValues, Inst,
InstRemovedStat)) {
MadeChanges = true;
}
}
Expand Down
9 changes: 3 additions & 6 deletions llvm/test/Transforms/SCCP/conditions-ranges-with-undef.ll
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Expand Up @@ -46,8 +46,7 @@ define void @val_undef_range() {
; CHECK-NEXT: br i1 [[BC_1]], label [[TRUE:%.*]], label [[FALSE:%.*]]
; CHECK: true:
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[A_127:%.*]] = and i32 [[A]], 127
; CHECK-NEXT: call void @use.i32(i32 [[A_127]])
; CHECK-NEXT: call void @use.i32(i32 [[A]])
; CHECK-NEXT: ret void
; CHECK: false:
; CHECK-NEXT: ret void
Expand Down Expand Up @@ -82,8 +81,7 @@ define void @val_singlecrfromundef_range(i1 %cond) {
; CHECK-NEXT: br label [[TRUE:%.*]]
; CHECK: true:
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[P_127:%.*]] = and i32 10, 127
; CHECK-NEXT: call void @use.i32(i32 [[P_127]])
; CHECK-NEXT: call void @use.i32(i32 10)
; CHECK-NEXT: ret void
;
entry:
Expand Down Expand Up @@ -131,8 +129,7 @@ define void @val_undef_to_cr_to_overdef_range(i32 %a, i1 %cond) {
; CHECK-NEXT: br i1 [[BC_1]], label [[TRUE:%.*]], label [[FALSE:%.*]]
; CHECK: true:
; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[P_127:%.*]] = and i32 [[P]], 127
; CHECK-NEXT: call void @use.i32(i32 [[P_127]])
; CHECK-NEXT: call void @use.i32(i32 [[P]])
; CHECK-NEXT: ret void
; CHECK: false:
; CHECK-NEXT: ret void
Expand Down
5 changes: 2 additions & 3 deletions llvm/test/Transforms/SCCP/range-and.ll
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@@ -1,4 +1,4 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --verbose
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -passes=sccp %s | FileCheck %s

declare void @use(i1)
Expand Down Expand Up @@ -140,9 +140,8 @@ define i64 @constant_range_and_255_100(i1 %cond, i64 %a) {
; CHECK-NEXT: br label [[BB3]]
; CHECK: bb3:
; CHECK-NEXT: [[P:%.*]] = phi i64 [ [[R_1]], [[BB1]] ], [ [[R_2]], [[BB2]] ]
; CHECK-NEXT: [[P_AND:%.*]] = and i64 [[P]], 255
; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: ret i64 [[P_AND]]
; CHECK-NEXT: ret i64 [[P]]
;
entry:
br i1 %cond, label %bb1, label %bb2
Expand Down
3 changes: 1 addition & 2 deletions llvm/test/Transforms/SCCP/range-with-undef.ll
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Expand Up @@ -12,8 +12,7 @@ define i8 @test_binop(i1 %cond, i8 %a) {
; CHECK-NEXT: [[A_EXT:%.*]] = zext i8 [[A]] to i16
; CHECK-NEXT: br label %[[JOIN]]
; CHECK: [[JOIN]]:
; CHECK-NEXT: [[PHI:%.*]] = phi i16 [ undef, %[[ENTRY]] ], [ [[A_EXT]], %[[IF]] ]
; CHECK-NEXT: [[AND:%.*]] = and i16 [[PHI]], -1
; CHECK-NEXT: [[AND:%.*]] = phi i16 [ undef, %[[ENTRY]] ], [ [[A_EXT]], %[[IF]] ]
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[AND]] to i8
; CHECK-NEXT: ret i8 [[TRUNC]]
;
Expand Down
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