[llvm] goldsteinn/cmp eq p2 neg p2 (PR #94867)
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Sat Jun 8 12:34:04 PDT 2024
https://github.com/goldsteinn created https://github.com/llvm/llvm-project/pull/94867
- **[InstCombine] Add tests for combining `(icmp eq/ne (and X, P2), (and X, -P2))`; NFC**
- **[InstCombine] Add combines for `(icmp eq/ne (and X, P2), (and X, -P2))`**
>From d8d186e6a892baa912ee7c27c9307dc373182229 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Sat, 8 Jun 2024 14:22:35 -0500
Subject: [PATCH 1/2] [InstCombine] Add tests for combining `(icmp eq/ne (and
X, P2), (and X, -P2))`; NFC
---
.../Transforms/InstCombine/and-compare.ll | 157 ++++++++++++++++++
1 file changed, 157 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/and-compare.ll b/llvm/test/Transforms/InstCombine/and-compare.ll
index 14379ebf3a905..e7b24bb0fc3f1 100644
--- a/llvm/test/Transforms/InstCombine/and-compare.ll
+++ b/llvm/test/Transforms/InstCombine/and-compare.ll
@@ -4,6 +4,8 @@
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
+declare void @use.i8(i8)
+
; Should be optimized to one and.
define i1 @test1(i32 %a, i32 %b) {
; CHECK-LABEL: @test1(
@@ -75,3 +77,158 @@ define <2 x i1> @test3vec(<2 x i64> %A) {
ret <2 x i1> %cmp
}
+define i1 @test_eq_p2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_eq_p2(
+; CHECK-NEXT: [[Y:%.*]] = shl nuw nsw i8 1, [[YY:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = add nsw i8 [[Y]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = shl nsw i8 1, %yy
+ %neg_y = sub i8 0, %y
+ %and_x_neg_y = and i8 %x, %neg_y
+ %and_x_y = and i8 %x, %y
+
+ %r = icmp eq i8 %and_x_y, %and_x_neg_y
+ ret i1 %r
+}
+
+define i1 @test_eq_p2_2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_eq_p2_2(
+; CHECK-NEXT: [[Y:%.*]] = shl nuw nsw i8 1, [[YY:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = add nsw i8 [[Y]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = shl nsw i8 1, %yy
+ %neg_y = sub i8 0, %y
+ %and_x_neg_y = and i8 %x, %neg_y
+ %and_x_y = and i8 %x, %y
+
+ %r = icmp eq i8 %and_x_neg_y, %and_x_y
+ ret i1 %r
+}
+
+define i1 @test_eq_p2_fail_maybe_zero(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_eq_p2_fail_maybe_zero(
+; CHECK-NEXT: [[Y:%.*]] = shl i8 2, [[YY:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %yyy = shl nsw i8 1, %yy
+ %y = add i8 %yyy, %yyy
+ %neg_y = sub nsw i8 0, %y
+ %and_x_neg_y = and i8 %x, %neg_y
+ %and_x_y = and i8 %x, %y
+
+ %r = icmp eq i8 %and_x_neg_y, %and_x_y
+ ret i1 %r
+}
+
+define i1 @test_eq_p2_fail_maybe_int_min(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_eq_p2_fail_maybe_int_min(
+; CHECK-NEXT: [[Y:%.*]] = shl nuw i8 1, [[YY:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[Y]], -1
+; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
+; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = shl i8 1, %yy
+ %neg_y = sub i8 0, %y
+ %and_x_neg_y = and i8 %x, %neg_y
+ %and_x_y = and i8 %x, %y
+
+ %r = icmp eq i8 %and_x_y, %and_x_neg_y
+ ret i1 %r
+}
+
+define i1 @test_eq_p2_fail_multiuse(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_eq_p2_fail_multiuse(
+; CHECK-NEXT: [[Y:%.*]] = shl nuw nsw i8 1, [[YY:%.*]]
+; CHECK-NEXT: [[NEG_Y:%.*]] = sub nsw i8 0, [[Y]]
+; CHECK-NEXT: [[AND_X_NEG_Y:%.*]] = and i8 [[NEG_Y]], [[X:%.*]]
+; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[Y]], [[X]]
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[AND_X_Y]], [[AND_X_NEG_Y]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %y = shl nsw i8 1, %yy
+ %neg_y = sub i8 0, %y
+ %and_x_neg_y = and i8 %x, %neg_y
+ %and_x_y = and i8 %x, %y
+ call void @use.i8(i8 %and_x_y)
+ %r = icmp eq i8 %and_x_y, %and_x_neg_y
+ ret i1 %r
+}
+
+define i1 @test_ne_cp2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_ne_cp2(
+; CHECK-NEXT: [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -16
+; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 16
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_NEG_Y]], [[AND_X_Y]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %and_x_neg_y = and i8 %x, -16
+ %and_x_y = and i8 %x, 16
+ call void @use.i8(i8 %and_x_neg_y)
+ call void @use.i8(i8 %and_x_y)
+ %r = icmp ne i8 %and_x_neg_y, %and_x_y
+ ret i1 %r
+}
+
+define i1 @test_ne_cp2_2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_ne_cp2_2(
+; CHECK-NEXT: [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -4
+; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 4
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_Y]], [[AND_X_NEG_Y]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %and_x_neg_y = and i8 %x, -4
+ %and_x_y = and i8 %x, 4
+ call void @use.i8(i8 %and_x_neg_y)
+ call void @use.i8(i8 %and_x_y)
+ %r = icmp ne i8 %and_x_y, %and_x_neg_y
+ ret i1 %r
+}
+
+define i1 @test_ne_cp2_other_fail(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_ne_cp2_other_fail(
+; CHECK-NEXT: [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -17
+; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 16
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_NEG_Y]], [[AND_X_Y]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %and_x_neg_y = and i8 %x, -17
+ %and_x_y = and i8 %x, 16
+ call void @use.i8(i8 %and_x_neg_y)
+ call void @use.i8(i8 %and_x_y)
+ %r = icmp ne i8 %and_x_neg_y, %and_x_y
+ ret i1 %r
+}
+
+define i1 @test_ne_cp2_other_fail2(i8 %x, i8 %yy) {
+; CHECK-LABEL: @test_ne_cp2_other_fail2(
+; CHECK-NEXT: [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -16
+; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 17
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
+; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_NEG_Y]], [[AND_X_Y]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %and_x_neg_y = and i8 %x, -16
+ %and_x_y = and i8 %x, 17
+ call void @use.i8(i8 %and_x_neg_y)
+ call void @use.i8(i8 %and_x_y)
+ %r = icmp ne i8 %and_x_neg_y, %and_x_y
+ ret i1 %r
+}
>From 970c0d69e8ebd55d2b21cd5ec215ee9c63c5495f Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Sat, 8 Jun 2024 14:22:37 -0500
Subject: [PATCH 2/2] [InstCombine] Add combines for `(icmp eq/ne (and X, P2),
(and X, -P2))`
`(icmp eq/ne (and X, P2), (and X, -P2))`
-> `(icmp ult/uge X, P2 * 2)`
If `P2` is constant, we can perform this fold profitably even if the
`and` ops are multi-use.
If `P2` is not constant, then we only perform the fold if the `and`
ops are multi-use. This, however, saves an instruction compared to the
`xor` + `and` variant.
NB: This came up in some of the diffs resulting from #94648
Proofs: https://alive2.llvm.org/ce/z/mfd3G9
---
.../InstCombine/InstCombineCompares.cpp | 38 ++++++++++++++++---
.../Transforms/InstCombine/and-compare.ll | 16 +++-----
2 files changed, 38 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 4203147bc6a54..e79913500f320 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5548,8 +5548,8 @@ Instruction *InstCombinerImpl::foldICmpEquality(ICmpInst &I) {
}
// (X&Z) == (Y&Z) -> (X^Y) & Z == 0
- if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
- match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
+ if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+ match(Op1, m_And(m_Value(C), m_Value(D)))) {
Value *X = nullptr, *Y = nullptr, *Z = nullptr;
if (A == C) {
@@ -5570,10 +5570,36 @@ Instruction *InstCombinerImpl::foldICmpEquality(ICmpInst &I) {
Z = B;
}
- if (X) { // Build (X^Y) & Z
- Op1 = Builder.CreateXor(X, Y);
- Op1 = Builder.CreateAnd(Op1, Z);
- return new ICmpInst(Pred, Op1, Constant::getNullValue(Op1->getType()));
+ if (X) {
+ // (X&P2) == (X&-P2)
+ // -> X u< P2*2
+ // (X&P2) != (X&-P2)
+ // -> X u>= P2*2
+ // iff P2 is not INT_MIN
+ const APInt *CP2;
+ ICmpInst::Predicate P2Pred =
+ Pred == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_UGE;
+ if (match(X, m_APInt(CP2)) && match(Y, m_SpecificInt(-*CP2)) &&
+ (CP2->isPowerOf2() || CP2->isNegatedPowerOf2()) &&
+ !CP2->isMinSignedValue()) {
+ APInt CMask = CP2->isPowerOf2() ? *CP2 : -*CP2;
+ return new ICmpInst(P2Pred, Z,
+ ConstantInt::get(Z->getType(), CMask + CMask));
+ }
+
+ if (Op0->hasOneUse() && Op1->hasOneUse()) {
+ // nsw neg precludes INT_MIN
+ if (match(X, m_NSWNeg(m_Specific(Y))))
+ std::swap(X, Y);
+ if (match(Y, m_NSWNeg(m_Specific(X))) &&
+ isKnownToBeAPowerOfTwo(X, /*OrZero=*/false, 0, &I))
+ return new ICmpInst(P2Pred, Z, Builder.CreateAdd(X, X));
+
+ // Build (X^Y) & Z
+ Op1 = Builder.CreateXor(X, Y);
+ Op1 = Builder.CreateAnd(Op1, Z);
+ return new ICmpInst(Pred, Op1, Constant::getNullValue(Op1->getType()));
+ }
}
}
diff --git a/llvm/test/Transforms/InstCombine/and-compare.ll b/llvm/test/Transforms/InstCombine/and-compare.ll
index e7b24bb0fc3f1..daadbf36d7577 100644
--- a/llvm/test/Transforms/InstCombine/and-compare.ll
+++ b/llvm/test/Transforms/InstCombine/and-compare.ll
@@ -79,10 +79,8 @@ define <2 x i1> @test3vec(<2 x i64> %A) {
define i1 @test_eq_p2(i8 %x, i8 %yy) {
; CHECK-LABEL: @test_eq_p2(
-; CHECK-NEXT: [[Y:%.*]] = shl nuw nsw i8 1, [[YY:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = add nsw i8 [[Y]], -1
-; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = shl i8 2, [[YY:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = shl nsw i8 1, %yy
@@ -96,10 +94,8 @@ define i1 @test_eq_p2(i8 %x, i8 %yy) {
define i1 @test_eq_p2_2(i8 %x, i8 %yy) {
; CHECK-LABEL: @test_eq_p2_2(
-; CHECK-NEXT: [[Y:%.*]] = shl nuw nsw i8 1, [[YY:%.*]]
-; CHECK-NEXT: [[TMP1:%.*]] = add nsw i8 [[Y]], -1
-; CHECK-NEXT: [[TMP2:%.*]] = xor i8 [[Y]], [[TMP1]]
-; CHECK-NEXT: [[R:%.*]] = icmp uge i8 [[TMP2]], [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = shl i8 2, [[YY:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[TMP1]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[R]]
;
%y = shl nsw i8 1, %yy
@@ -171,7 +167,7 @@ define i1 @test_ne_cp2(i8 %x, i8 %yy) {
; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 16
; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
-; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_NEG_Y]], [[AND_X_Y]]
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[X]], 31
; CHECK-NEXT: ret i1 [[R]]
;
%and_x_neg_y = and i8 %x, -16
@@ -188,7 +184,7 @@ define i1 @test_ne_cp2_2(i8 %x, i8 %yy) {
; CHECK-NEXT: [[AND_X_Y:%.*]] = and i8 [[X]], 4
; CHECK-NEXT: call void @use.i8(i8 [[AND_X_NEG_Y]])
; CHECK-NEXT: call void @use.i8(i8 [[AND_X_Y]])
-; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[AND_X_Y]], [[AND_X_NEG_Y]]
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[X]], 7
; CHECK-NEXT: ret i1 [[R]]
;
%and_x_neg_y = and i8 %x, -4
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