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[InstCombine] Simplify and/or of icmp eq with op replacement
and/or in logical (select) form benefit from generic simplifications via simplifyWithOpReplaced(). However, the corresponding fold for plain and/or currently does not exist. Similar to selects, there are two general cases for this fold (illustrated with `and`, but there are `or` conjugates). The basic case is something like `(a == b) & c`, where the replacement of a with b or b with a inside c allows it to fold to true or false. Then the whole operation will fold to either false or `a == b`. The second case is something like `(a != b) & c`, where the replacement inside c allows it to fold to false. In that case, the operand can be replaced with c, because in the case where a == b (and thus the icmp is false), c itself will already be false. As the test diffs show, this catches quite a lot of patterns in existing test coverage. I believe this also obsoletes quite a few existing special-case and/or of icmp special case folds we have, but I haven't removed anything as part of this patch in the interest of risk mitigation.
1 parent ea1909f commit 8a1d0a6

14 files changed

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lines changed

‎llvm/lib/Analysis/InstructionSimplify.cpp

Lines changed: 60 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2025,6 +2025,52 @@ static Value *simplifyAndOrOfCmps(const SimplifyQuery &Q, Value *Op0,
20252025
return nullptr;
20262026
}
20272027

2028+
static Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
2029+
const SimplifyQuery &Q,
2030+
bool AllowRefinement,
2031+
SmallVectorImpl<Instruction *> *DropFlags,
2032+
unsigned MaxRecurse);
2033+
2034+
static Value *simplifyAndOrWithICmpEq(unsigned Opcode, Value *Op0, Value *Op1,
2035+
const SimplifyQuery &Q,
2036+
unsigned MaxRecurse) {
2037+
assert((Opcode == Instruction::And || Opcode == Instruction::Or) &&
2038+
"Must be and/or");
2039+
ICmpInst::Predicate Pred;
2040+
Value *A, *B;
2041+
if (!match(Op0, m_ICmp(Pred, m_Value(A), m_Value(B))) ||
2042+
!ICmpInst::isEquality(Pred) || !MaxRecurse--)
2043+
return nullptr;
2044+
2045+
auto Simplify = [&](Value *Res) -> Value * {
2046+
// and (icmp eq a, b), x implies (a==b) inside x.
2047+
// or (icmp ne a, b), x implies (a==b) inside x.
2048+
// If x simplifies to true/false, we can simplify the and/or.
2049+
if (Pred ==
2050+
(Opcode == Instruction::And ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE))
2051+
return simplifyBinOp(Opcode, Op0, Res, Q, MaxRecurse);
2052+
// If we have and (icmp ne a, b), x and for a==b we can simplify x to false,
2053+
// then we can drop the icmp, as x will already be false in the case where
2054+
// the icmp is false. Similar for or and true.
2055+
if (Res == ConstantExpr::getBinOpAbsorber(Opcode, Res->getType()))
2056+
return Op1;
2057+
return nullptr;
2058+
};
2059+
2060+
// Increment MaxRecurse again, because simplifyWithOpReplaced() does its own
2061+
// decrement.
2062+
if (Value *Res =
2063+
simplifyWithOpReplaced(Op1, A, B, Q, /* AllowRefinement */ true,
2064+
/* DropFlags */ nullptr, MaxRecurse + 1))
2065+
return Simplify(Res);
2066+
if (Value *Res =
2067+
simplifyWithOpReplaced(Op1, B, A, Q, /* AllowRefinement */ true,
2068+
/* DropFlags */ nullptr, MaxRecurse + 1))
2069+
return Simplify(Res);
2070+
2071+
return nullptr;
2072+
}
2073+
20282074
/// Given a bitwise logic op, check if the operands are add/sub with a common
20292075
/// source value and inverted constant (identity: C - X -> ~(X + ~C)).
20302076
static Value *simplifyLogicOfAddSub(Value *Op0, Value *Op1,
@@ -2159,6 +2205,13 @@ static Value *simplifyAndInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
21592205
isKnownToBeAPowerOfTwo(Op0, Q.DL, /*OrZero*/ true, 0, Q.AC, Q.CxtI, Q.DT))
21602206
return Constant::getNullValue(Op0->getType());
21612207

2208+
if (Value *V =
2209+
simplifyAndOrWithICmpEq(Instruction::And, Op0, Op1, Q, MaxRecurse))
2210+
return V;
2211+
if (Value *V =
2212+
simplifyAndOrWithICmpEq(Instruction::And, Op1, Op0, Q, MaxRecurse))
2213+
return V;
2214+
21622215
if (Value *V = simplifyAndOrOfCmps(Q, Op0, Op1, true))
21632216
return V;
21642217

@@ -2435,6 +2488,13 @@ static Value *simplifyOrInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
24352488
match(Op0, m_LShr(m_Specific(X), m_Specific(Y))))
24362489
return Op1;
24372490

2491+
if (Value *V =
2492+
simplifyAndOrWithICmpEq(Instruction::Or, Op0, Op1, Q, MaxRecurse))
2493+
return V;
2494+
if (Value *V =
2495+
simplifyAndOrWithICmpEq(Instruction::Or, Op1, Op0, Q, MaxRecurse))
2496+
return V;
2497+
24382498
if (Value *V = simplifyAndOrOfCmps(Q, Op0, Op1, false))
24392499
return V;
24402500

‎llvm/test/CodeGen/PowerPC/pr45448.ll

Lines changed: 3 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -20,20 +20,16 @@ define hidden void @julia_tryparse_internal_45896() #0 {
2020
; CHECK-NEXT: .LBB0_6: # %fail194
2121
; CHECK-NEXT: .LBB0_7: # %L670
2222
; CHECK-NEXT: li r5, -3
23-
; CHECK-NEXT: cmpdi r3, 0
2423
; CHECK-NEXT: sradi r4, r3, 63
2524
; CHECK-NEXT: rldic r5, r5, 4, 32
26-
; CHECK-NEXT: crnot 4*cr5+lt, eq
2725
; CHECK-NEXT: mulhdu r3, r3, r5
2826
; CHECK-NEXT: maddld r6, r4, r5, r3
2927
; CHECK-NEXT: cmpld cr1, r6, r3
3028
; CHECK-NEXT: mulhdu. r3, r4, r5
31-
; CHECK-NEXT: bc 4, 4*cr5+lt, .LBB0_10
32-
; CHECK-NEXT: # %bb.8: # %L670
3329
; CHECK-NEXT: crorc 4*cr5+lt, 4*cr1+lt, eq
34-
; CHECK-NEXT: bc 4, 4*cr5+lt, .LBB0_10
35-
; CHECK-NEXT: # %bb.9: # %L917
36-
; CHECK-NEXT: .LBB0_10: # %L994
30+
; CHECK-NEXT: bc 4, 4*cr5+lt, .LBB0_9
31+
; CHECK-NEXT: # %bb.8: # %L917
32+
; CHECK-NEXT: .LBB0_9: # %L994
3733
top:
3834
%0 = load i64, ptr undef, align 8
3935
%1 = icmp ne i64 %0, 0

‎llvm/test/Transforms/InstCombine/div-by-0-guard-before-smul_ov.ll

Lines changed: 2 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -47,11 +47,7 @@ define i1 @n2_wrong_size(i4 %size0, i4 %size1, i4 %nmemb) {
4747

4848
define i1 @n3_wrong_pred(i4 %size, i4 %nmemb) {
4949
; CHECK-LABEL: @n3_wrong_pred(
50-
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i4 [[SIZE:%.*]], 0
51-
; CHECK-NEXT: [[SMUL:%.*]] = tail call { i4, i1 } @llvm.smul.with.overflow.i4(i4 [[SIZE]], i4 [[NMEMB:%.*]])
52-
; CHECK-NEXT: [[SMUL_OV:%.*]] = extractvalue { i4, i1 } [[SMUL]], 1
53-
; CHECK-NEXT: [[AND:%.*]] = and i1 [[SMUL_OV]], [[CMP]]
54-
; CHECK-NEXT: ret i1 [[AND]]
50+
; CHECK-NEXT: ret i1 false
5551
;
5652
%cmp = icmp eq i4 %size, 0 ; not 'ne'
5753
%smul = tail call { i4, i1 } @llvm.smul.with.overflow.i4(i4 %size, i4 %nmemb)
@@ -63,10 +59,7 @@ define i1 @n3_wrong_pred(i4 %size, i4 %nmemb) {
6359
define i1 @n4_not_and(i4 %size, i4 %nmemb) {
6460
; CHECK-LABEL: @n4_not_and(
6561
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i4 [[SIZE:%.*]], 0
66-
; CHECK-NEXT: [[SMUL:%.*]] = tail call { i4, i1 } @llvm.smul.with.overflow.i4(i4 [[SIZE]], i4 [[NMEMB:%.*]])
67-
; CHECK-NEXT: [[SMUL_OV:%.*]] = extractvalue { i4, i1 } [[SMUL]], 1
68-
; CHECK-NEXT: [[AND:%.*]] = or i1 [[SMUL_OV]], [[CMP]]
69-
; CHECK-NEXT: ret i1 [[AND]]
62+
; CHECK-NEXT: ret i1 [[CMP]]
7063
;
7164
%cmp = icmp ne i4 %size, 0
7265
%smul = tail call { i4, i1 } @llvm.smul.with.overflow.i4(i4 %size, i4 %nmemb)

‎llvm/test/Transforms/InstCombine/div-by-0-guard-before-umul_ov.ll

Lines changed: 2 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -47,11 +47,7 @@ define i1 @n2_wrong_size(i4 %size0, i4 %size1, i4 %nmemb) {
4747

4848
define i1 @n3_wrong_pred(i4 %size, i4 %nmemb) {
4949
; CHECK-LABEL: @n3_wrong_pred(
50-
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i4 [[SIZE:%.*]], 0
51-
; CHECK-NEXT: [[UMUL:%.*]] = tail call { i4, i1 } @llvm.umul.with.overflow.i4(i4 [[SIZE]], i4 [[NMEMB:%.*]])
52-
; CHECK-NEXT: [[UMUL_OV:%.*]] = extractvalue { i4, i1 } [[UMUL]], 1
53-
; CHECK-NEXT: [[AND:%.*]] = and i1 [[UMUL_OV]], [[CMP]]
54-
; CHECK-NEXT: ret i1 [[AND]]
50+
; CHECK-NEXT: ret i1 false
5551
;
5652
%cmp = icmp eq i4 %size, 0 ; not 'ne'
5753
%umul = tail call { i4, i1 } @llvm.umul.with.overflow.i4(i4 %size, i4 %nmemb)
@@ -63,10 +59,7 @@ define i1 @n3_wrong_pred(i4 %size, i4 %nmemb) {
6359
define i1 @n4_not_and(i4 %size, i4 %nmemb) {
6460
; CHECK-LABEL: @n4_not_and(
6561
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i4 [[SIZE:%.*]], 0
66-
; CHECK-NEXT: [[UMUL:%.*]] = tail call { i4, i1 } @llvm.umul.with.overflow.i4(i4 [[SIZE]], i4 [[NMEMB:%.*]])
67-
; CHECK-NEXT: [[UMUL_OV:%.*]] = extractvalue { i4, i1 } [[UMUL]], 1
68-
; CHECK-NEXT: [[AND:%.*]] = or i1 [[UMUL_OV]], [[CMP]]
69-
; CHECK-NEXT: ret i1 [[AND]]
62+
; CHECK-NEXT: ret i1 [[CMP]]
7063
;
7164
%cmp = icmp ne i4 %size, 0
7265
%umul = tail call { i4, i1 } @llvm.umul.with.overflow.i4(i4 %size, i4 %nmemb)

‎llvm/test/Transforms/InstCombine/ispow2.ll

Lines changed: 5 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -392,9 +392,7 @@ define i1 @is_pow2_ctpop_wrong_pred1(i32 %x) {
392392
; CHECK-LABEL: @is_pow2_ctpop_wrong_pred1(
393393
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range [[RNG0]]
394394
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[T0]], 2
395-
; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne i32 [[X]], 0
396-
; CHECK-NEXT: [[R:%.*]] = and i1 [[NOTZERO]], [[CMP]]
397-
; CHECK-NEXT: ret i1 [[R]]
395+
; CHECK-NEXT: ret i1 [[CMP]]
398396
;
399397
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
400398
%cmp = icmp ugt i32 %t0, 2
@@ -946,9 +944,7 @@ define i1 @is_pow2or0_ctpop_wrong_pred1(i32 %x) {
946944
; CHECK-LABEL: @is_pow2or0_ctpop_wrong_pred1(
947945
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range [[RNG0]]
948946
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[T0]], 1
949-
; CHECK-NEXT: [[ISZERO:%.*]] = icmp eq i32 [[X]], 0
950-
; CHECK-NEXT: [[R:%.*]] = or i1 [[ISZERO]], [[CMP]]
951-
; CHECK-NEXT: ret i1 [[R]]
947+
; CHECK-NEXT: ret i1 [[CMP]]
952948
;
953949
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
954950
%cmp = icmp ne i32 %t0, 1
@@ -959,11 +955,7 @@ define i1 @is_pow2or0_ctpop_wrong_pred1(i32 %x) {
959955

960956
define i1 @is_pow2or0_ctpop_wrong_pred2(i32 %x) {
961957
; CHECK-LABEL: @is_pow2or0_ctpop_wrong_pred2(
962-
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range [[RNG0]]
963-
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[T0]], 1
964-
; CHECK-NEXT: [[ISZERO:%.*]] = icmp ne i32 [[X]], 0
965-
; CHECK-NEXT: [[R:%.*]] = or i1 [[ISZERO]], [[CMP]]
966-
; CHECK-NEXT: ret i1 [[R]]
958+
; CHECK-NEXT: ret i1 true
967959
;
968960
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
969961
%cmp = icmp ne i32 %t0, 1
@@ -1149,9 +1141,7 @@ define i1 @isnot_pow2nor0_ctpop_wrong_pred1(i32 %x) {
11491141
; CHECK-LABEL: @isnot_pow2nor0_ctpop_wrong_pred1(
11501142
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range [[RNG0]]
11511143
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[T0]], 1
1152-
; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne i32 [[X]], 0
1153-
; CHECK-NEXT: [[R:%.*]] = and i1 [[NOTZERO]], [[CMP]]
1154-
; CHECK-NEXT: ret i1 [[R]]
1144+
; CHECK-NEXT: ret i1 [[CMP]]
11551145
;
11561146
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
11571147
%cmp = icmp eq i32 %t0, 1
@@ -1162,11 +1152,7 @@ define i1 @isnot_pow2nor0_ctpop_wrong_pred1(i32 %x) {
11621152

11631153
define i1 @isnot_pow2nor0_ctpop_wrong_pred2(i32 %x) {
11641154
; CHECK-LABEL: @isnot_pow2nor0_ctpop_wrong_pred2(
1165-
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]]), !range [[RNG0]]
1166-
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[T0]], 1
1167-
; CHECK-NEXT: [[NOTZERO:%.*]] = icmp eq i32 [[X]], 0
1168-
; CHECK-NEXT: [[R:%.*]] = and i1 [[NOTZERO]], [[CMP]]
1169-
; CHECK-NEXT: ret i1 [[R]]
1155+
; CHECK-NEXT: ret i1 false
11701156
;
11711157
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
11721158
%cmp = icmp eq i32 %t0, 1

‎llvm/test/Transforms/InstSimplify/and-or-icmp-ctpop.ll

Lines changed: 2 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -40,11 +40,7 @@ define <2 x i1> @eq_or_non_0_commute(<2 x i32> %x) {
4040

4141
define i1 @eq_or_non_0_wrong_pred1(i32 %x) {
4242
; CHECK-LABEL: @eq_or_non_0_wrong_pred1(
43-
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]])
44-
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[T0]], 10
45-
; CHECK-NEXT: [[NOTZERO:%.*]] = icmp ne i32 [[X]], 0
46-
; CHECK-NEXT: [[R:%.*]] = or i1 [[NOTZERO]], [[CMP]]
47-
; CHECK-NEXT: ret i1 [[R]]
43+
; CHECK-NEXT: ret i1 true
4844
;
4945
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
5046
%cmp = icmp ne i32 %t0, 10
@@ -90,9 +86,7 @@ define i1 @ne_and_is_0_wrong_pred1(i32 %x) {
9086
; CHECK-LABEL: @ne_and_is_0_wrong_pred1(
9187
; CHECK-NEXT: [[T0:%.*]] = tail call i32 @llvm.ctpop.i32(i32 [[X:%.*]])
9288
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[T0]], 10
93-
; CHECK-NEXT: [[ISZERO:%.*]] = icmp eq i32 [[X]], 0
94-
; CHECK-NEXT: [[R:%.*]] = or i1 [[ISZERO]], [[CMP]]
95-
; CHECK-NEXT: ret i1 [[R]]
89+
; CHECK-NEXT: ret i1 [[CMP]]
9690
;
9791
%t0 = tail call i32 @llvm.ctpop.i32(i32 %x)
9892
%cmp = icmp ne i32 %t0, 10

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