[llvm] goldsteinn/sub non eq (PR #87704)
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Thu Apr 4 13:39:06 PDT 2024
https://github.com/goldsteinn created https://github.com/llvm/llvm-project/pull/87704
- **[ValueTracking] Add tests for `sub` in `isKnownNonEqual`; NFC**
- **[ValueTracking] Add support for `sub` in `isKnownNonEqual`**
>From 857ce4efb7da0470e7e6c4892000798536f2eef8 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Wed, 3 Apr 2024 21:41:37 -0500
Subject: [PATCH 1/2] [ValueTracking] Add tests for `sub` in `isKnownNonEqual`;
NFC
---
llvm/test/Transforms/InstSimplify/icmp.ll | 119 +++++++++++++++++++++-
1 file changed, 118 insertions(+), 1 deletion(-)
diff --git a/llvm/test/Transforms/InstSimplify/icmp.ll b/llvm/test/Transforms/InstSimplify/icmp.ll
index 3109768bdfe005..fd90987dda3d23 100644
--- a/llvm/test/Transforms/InstSimplify/icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/icmp.ll
@@ -270,7 +270,7 @@ define i1 @load_ptr(ptr %p) {
define i1 @load_ptr_null_valid(ptr %p) null_pointer_is_valid {
; CHECK-LABEL: @load_ptr_null_valid(
-; CHECK-NEXT: [[LOAD_P:%.*]] = load ptr, ptr [[P:%.*]], align 8, !dereferenceable !0
+; CHECK-NEXT: [[LOAD_P:%.*]] = load ptr, ptr [[P:%.*]], align 8, !dereferenceable [[META0:![0-9]+]]
; CHECK-NEXT: [[R:%.*]] = icmp ne ptr [[LOAD_P]], null
; CHECK-NEXT: ret i1 [[R]]
;
@@ -278,3 +278,120 @@ define i1 @load_ptr_null_valid(ptr %p) null_pointer_is_valid {
%r = icmp ne ptr %load_p, null
ret i1 %r
}
+
+define i1 @non_eq_sub_neg_case_nsw(i8 %x, i8 %yy) {
+; CHECK-LABEL: @non_eq_sub_neg_case_nsw(
+; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub nsw i8 0, [[Y]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = add nuw i8 %yy, 1
+ %lhs = add i8 %x, %y
+ %suby = sub nsw i8 0, %y
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub_neg_case_no_intmin(i8 %x, i8 %yy) {
+; CHECK-LABEL: @non_eq_sub_neg_case_no_intmin(
+; CHECK-NEXT: [[Y0:%.*]] = and i8 [[YY:%.*]], 63
+; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[Y0]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub i8 0, [[Y]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y0 = and i8 %yy, 63
+ %y = add nuw i8 %y0, 1
+ %lhs = add i8 %x, %y
+ %suby = sub i8 0, %y
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub_neg_case_no_intmin2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @non_eq_sub_neg_case_no_intmin2(
+; CHECK-NEXT: ret i1 false
+;
+ %y = or i8 %yy, -64
+ %lhs = add i8 %x, %y
+ %suby = sub i8 0, %y
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub_neg_case_fail(i8 %x, i8 %yy) {
+; CHECK-LABEL: @non_eq_sub_neg_case_fail(
+; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub i8 0, [[Y]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = add nuw i8 %yy, 1
+ %lhs = add i8 %x, %y
+ %suby = sub i8 0, %y
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub(i8 %x, i8 %yy, i8 %z) {
+; CHECK-LABEL: @non_eq_sub(
+; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub i8 [[Z]], [[Y]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = add nuw i8 %yy, 1
+ %lhs = add i8 %x, %z
+ %suby = sub i8 %z, %y
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub2(i8 %x, i8 %yy, i8 %z) {
+; CHECK-LABEL: @non_eq_sub2(
+; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub i8 [[Y]], [[Z]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = add nuw i8 %yy, 1
+ %lhs = add i8 %x, %z
+ %suby = sub i8 %y, %z
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
+define i1 @non_eq_sub2_fail(i8 %x, i8 %yy, i8 %z) {
+; CHECK-LABEL: @non_eq_sub2_fail(
+; CHECK-NEXT: [[Y:%.*]] = add nsw i8 [[YY:%.*]], 1
+; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[SUBY:%.*]] = sub i8 [[Y]], [[Z]]
+; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = add nsw i8 %yy, 1
+ %lhs = add i8 %x, %z
+ %suby = sub i8 %y, %z
+ %rhs = add i8 %x, %suby
+ %r = icmp eq i8 %lhs, %rhs
+ ret i1 %r
+}
+
>From 6022988afc1c3d6d7b0f4f40c545ecca86a5f6c6 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Wed, 3 Apr 2024 17:38:48 -0500
Subject: [PATCH 2/2] [ValueTracking] Add support for `sub` in
`isKnownNonEqual`
There are several cases we can handle.
1) `-X != X` if `X != 0 && X != INT_MIN`
2) `X - Y != X` if `Y != 0`
3) `Y - X != X` if `Y != 0`
Proofs: https://alive2.llvm.org/ce/z/Vi3_Bd
---
llvm/lib/Analysis/ValueTracking.cpp | 42 ++++++++++++++++++++---
llvm/test/Transforms/InstSimplify/icmp.ll | 33 +++---------------
2 files changed, 43 insertions(+), 32 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 5ad4da43bca7db..dc9490180997c7 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2456,10 +2456,11 @@ static bool isNonZeroAdd(const APInt &DemandedElts, unsigned Depth,
static bool isNonZeroSub(const APInt &DemandedElts, unsigned Depth,
const SimplifyQuery &Q, unsigned BitWidth, Value *X,
Value *Y) {
- // TODO: Move this case into isKnownNonEqual().
- if (auto *C = dyn_cast<Constant>(X))
- if (C->isNullValue() && isKnownNonZero(Y, DemandedElts, Depth, Q))
- return true;
+ // We duplicate this case with isKnownNonEqual because we have DemandedElts
+ // here but not in isKnownNonEqual.
+ // If we add support for DemandedElts in isKnownNonEqual, drop this case.
+ if (match(X, m_Zero()))
+ return isKnownNonZero(Y, DemandedElts, Depth, Q);
return ::isKnownNonEqual(X, Y, Depth, Q);
}
@@ -3134,6 +3135,36 @@ static bool isNonEqualShl(const Value *V1, const Value *V2, unsigned Depth,
return false;
}
+/// Return true if V1 == V2 - X or V1 == X - V2 implies V2 != V1
+static bool isNonEqualSub(const Value *V1, const Value *V2, unsigned Depth,
+ const SimplifyQuery &Q) {
+ const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
+ if (!BO || BO->getOpcode() != Instruction::Sub)
+ return false;
+
+ // -V2 != V2 iff V2 != 0 and V2 != INT_MIN
+ if (match(BO, m_Sub(m_Zero(), m_Specific(V2)))) {
+ const OverflowingBinaryOperator *OBO = cast<OverflowingBinaryOperator>(V1);
+ // nsw implies no INT_MIN case.
+ if (OBO->hasNoSignedWrap())
+ return isKnownNonZero(V2, Depth + 1, Q);
+ // Otherwise check for INT_MIN case directly.
+ KnownBits V2Known = computeKnownBits(V2, Depth + 1, Q);
+ if (V2Known.isNonNegative() ||
+ (!V2Known.One.isZero() && !V2Known.One.isMinSignedValue()))
+ return V2Known.isNonZero() || isKnownNonZero(V2, Depth + 1, Q);
+ }
+
+ // X - V2 != V2 if X != 0
+ if (V2 == BO->getOperand(0))
+ return isKnownNonZero(BO->getOperand(1), Depth + 1, Q);
+ if (V2 == BO->getOperand(1))
+ return isKnownNonZero(BO->getOperand(0), Depth + 1, Q);
+
+ return false;
+}
+
+
static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
unsigned Depth, const SimplifyQuery &Q) {
// Check two PHIs are in same block.
@@ -3274,6 +3305,9 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
if (isNonEqualShl(V1, V2, Depth, Q) || isNonEqualShl(V2, V1, Depth, Q))
return true;
+ if (isNonEqualSub(V1, V2, Depth, Q) || isNonEqualSub(V2, V1, Depth, Q))
+ return true;
+
if (V1->getType()->isIntOrIntVectorTy()) {
// Are any known bits in V1 contradictory to known bits in V2? If V1
// has a known zero where V2 has a known one, they must not be equal.
diff --git a/llvm/test/Transforms/InstSimplify/icmp.ll b/llvm/test/Transforms/InstSimplify/icmp.ll
index fd90987dda3d23..699262b074e0d2 100644
--- a/llvm/test/Transforms/InstSimplify/icmp.ll
+++ b/llvm/test/Transforms/InstSimplify/icmp.ll
@@ -250,9 +250,7 @@ define <2 x i1> @sub_odd_poison(<2 x i8> %x) {
define i1 @sub_even(i8 %x) {
; CHECK-LABEL: @sub_even(
-; CHECK-NEXT: [[SUB:%.*]] = sub i8 2, [[X:%.*]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp ne i8 [[SUB]], [[X]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%sub = sub i8 2, %x
%cmp = icmp ne i8 %sub, %x
@@ -281,12 +279,7 @@ define i1 @load_ptr_null_valid(ptr %p) null_pointer_is_valid {
define i1 @non_eq_sub_neg_case_nsw(i8 %x, i8 %yy) {
; CHECK-LABEL: @non_eq_sub_neg_case_nsw(
-; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
-; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y]]
-; CHECK-NEXT: [[SUBY:%.*]] = sub nsw i8 0, [[Y]]
-; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %y
@@ -298,13 +291,7 @@ define i1 @non_eq_sub_neg_case_nsw(i8 %x, i8 %yy) {
define i1 @non_eq_sub_neg_case_no_intmin(i8 %x, i8 %yy) {
; CHECK-LABEL: @non_eq_sub_neg_case_no_intmin(
-; CHECK-NEXT: [[Y0:%.*]] = and i8 [[YY:%.*]], 63
-; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[Y0]], 1
-; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Y]]
-; CHECK-NEXT: [[SUBY:%.*]] = sub i8 0, [[Y]]
-; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%y0 = and i8 %yy, 63
%y = add nuw i8 %y0, 1
@@ -346,12 +333,7 @@ define i1 @non_eq_sub_neg_case_fail(i8 %x, i8 %yy) {
define i1 @non_eq_sub(i8 %x, i8 %yy, i8 %z) {
; CHECK-LABEL: @non_eq_sub(
-; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
-; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
-; CHECK-NEXT: [[SUBY:%.*]] = sub i8 [[Z]], [[Y]]
-; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %z
@@ -363,12 +345,7 @@ define i1 @non_eq_sub(i8 %x, i8 %yy, i8 %z) {
define i1 @non_eq_sub2(i8 %x, i8 %yy, i8 %z) {
; CHECK-LABEL: @non_eq_sub2(
-; CHECK-NEXT: [[Y:%.*]] = add nuw i8 [[YY:%.*]], 1
-; CHECK-NEXT: [[LHS:%.*]] = add i8 [[X:%.*]], [[Z:%.*]]
-; CHECK-NEXT: [[SUBY:%.*]] = sub i8 [[Y]], [[Z]]
-; CHECK-NEXT: [[RHS:%.*]] = add i8 [[X]], [[SUBY]]
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[LHS]], [[RHS]]
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%y = add nuw i8 %yy, 1
%lhs = add i8 %x, %z
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