[ValueTracking] Improve knownbits from conditions where Val is used by and/or.
#86059
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@llvm/pr-subscribers-llvm-analysis @llvm/pr-subscribers-llvm-transforms Author: None (goldsteinn) Changes
Full diff: https://github.com/llvm/llvm-project/pull/86059.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 797665cf06c875..ade8fef385ec15 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -698,13 +698,26 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
break;
}
default:
- const APInt *Offset = nullptr;
- if (match(LHS, m_CombineOr(m_V, m_Add(m_V, m_APInt(Offset)))) &&
- match(RHS, m_APInt(C))) {
- ConstantRange LHSRange = ConstantRange::makeAllowedICmpRegion(Pred, *C);
- if (Offset)
- LHSRange = LHSRange.sub(*Offset);
- Known = Known.unionWith(LHSRange.toKnownBits());
+ if (match(RHS, m_APInt(C))) {
+ const APInt *Offset = nullptr;
+ if (match(LHS, m_CombineOr(m_V, m_AddLike(m_V, m_APInt(Offset))))) {
+ ConstantRange LHSRange = ConstantRange::makeAllowedICmpRegion(Pred, *C);
+ if (Offset)
+ LHSRange = LHSRange.sub(*Offset);
+ Known = Known.unionWith(LHSRange.toKnownBits());
+ }
+ // X & Y u> C -> X u> C && Y u> C
+ if ((Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) &&
+ match(LHS, m_c_And(m_V, m_Value()))) {
+ Known.One.setHighBits(
+ (*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
+ }
+ // X | Y u< C -> X u< C && Y u< C
+ if ((Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) &&
+ match(LHS, m_c_Or(m_V, m_Value()))) {
+ Known.Zero.setHighBits(
+ (*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
+ }
}
break;
}
@@ -9283,11 +9296,22 @@ void llvm::findValuesAffectedByCondition(
AddAffected(X);
}
} else {
- // Handle (A + C1) u< C2, which is the canonical form of
- // A > C3 && A < C4.
- if (match(A, m_Add(m_Value(X), m_ConstantInt())) &&
- match(B, m_ConstantInt()))
- AddAffected(X);
+ if (match(B, m_ConstantInt())) {
+ // Handle (A + C1) u< C2, which is the canonical form of
+ // A > C3 && A < C4.
+ if (match(A, m_AddLike(m_Value(X), m_ConstantInt())))
+ AddAffected(X);
+
+ Value *Y;
+ // X & Y u> C -> X >u C && Y >u C
+ // X | Y u< C -> X u< C && Y u< C
+ if (ICmpInst::isUnsigned(Pred) &&
+ (match(A, m_And(m_Value(X), m_Value(Y))) ||
+ match(A, m_Or(m_Value(X), m_Value(Y))))) {
+ AddAffected(X);
+ AddAffected(Y);
+ }
+ }
// Handle icmp slt/sgt (bitcast X to int), 0/-1, which is supported
// by computeKnownFPClass().
diff --git a/llvm/test/Transforms/InstCombine/known-bits.ll b/llvm/test/Transforms/InstCombine/known-bits.ll
index 58c283815cf910..ad0c2c06eea91d 100644
--- a/llvm/test/Transforms/InstCombine/known-bits.ll
+++ b/llvm/test/Transforms/InstCombine/known-bits.ll
@@ -483,5 +483,251 @@ if.else:
ret i64 13
}
+define i1 @test_icmp_or_distjoint(i8 %n, i1 %other) {
+; CHECK-LABEL: @test_icmp_or_distjoint(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or disjoint i8 [[N:%.*]], 16
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_OR]], -111
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i1 true
+; CHECK: if.else:
+; CHECK-NEXT: ret i1 [[OTHER:%.*]]
+;
+entry:
+ %n_or = or disjoint i8 %n, 16
+ %cmp = icmp ugt i8 %n_or, 145
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = icmp slt i8 %n, 0
+ ret i1 %r
+
+if.else:
+ ret i1 %other
+}
+
+define i1 @test_icmp_or_fail_missing_disjoint(i8 %n, i1 %other) {
+; CHECK-LABEL: @test_icmp_or_fail_missing_disjoint(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or i8 [[N:%.*]], 16
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_OR]], -111
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[R:%.*]] = icmp slt i8 [[N]], 0
+; CHECK-NEXT: ret i1 [[R]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i1 [[OTHER:%.*]]
+;
+entry:
+ %n_or = or i8 %n, 16
+ %cmp = icmp ugt i8 %n_or, 145
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = icmp slt i8 %n, 0
+ ret i1 %r
+
+if.else:
+ ret i1 %other
+}
+
+define i8 @test_icmp_or(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_or(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_OR]], 32
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i8 0
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_or = or i8 %n, %n2
+ %cmp = icmp ult i8 %n_or, 32
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+define i8 @test_icmp_or2(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_or2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_OR]], 14
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 0
+;
+entry:
+ %n_or = or i8 %n, %n2
+ %cmp = icmp uge i8 %n_or, 15
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ ret i8 %other
+if.else:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+}
+
+define i8 @test_icmp_or_fail_bad_range(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_or_fail_bad_range(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_OR]], 33
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
+; CHECK-NEXT: ret i8 [[R]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_or = or i8 %n, %n2
+ %cmp = icmp ule i8 %n_or, 32
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+define i8 @test_icmp_or_fail_bad_pred(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_or_fail_bad_pred(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_OR:%.*]] = or i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_OR]], 32
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
+; CHECK-NEXT: ret i8 [[R]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_or = or i8 %n, %n2
+ %cmp = icmp ugt i8 %n_or, 32
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+define i8 @test_icmp_and(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_and(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_AND:%.*]] = and i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_AND]], -33
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i8 32
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_and = and i8 %n, %n2
+ %cmp = icmp ugt i8 %n_and, 223
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+define i8 @test_icmp_and2(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_and2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_AND:%.*]] = and i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_AND]], -31
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 32
+;
+entry:
+ %n_and = and i8 %n, %n2
+ %cmp = icmp ule i8 %n_and, 224
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ ret i8 %other
+if.else:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+}
+
+define i8 @test_icmp_and_fail_bad_range(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_and_fail_bad_range(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_AND:%.*]] = and i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_AND]], -34
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
+; CHECK-NEXT: ret i8 [[R]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_and = and i8 %n, %n2
+ %cmp = icmp uge i8 %n_and, 223
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+define i8 @test_icmp_and_fail_bad_pred(i8 %n, i8 %n2, i8 %other) {
+; CHECK-LABEL: @test_icmp_and_fail_bad_pred(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[N_AND:%.*]] = and i8 [[N:%.*]], [[N2:%.*]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[N_AND]], 32
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
+; CHECK-NEXT: ret i8 [[R]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i8 [[OTHER:%.*]]
+;
+entry:
+ %n_and = and i8 %n, %n2
+ %cmp = icmp eq i8 %n_and, 32
+ br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+ %r = and i8 %n, 32
+ ret i8 %r
+
+if.else:
+ ret i8 %other
+}
+
+
declare void @use(i1)
declare void @sink(i8)
|
goldsteinn
changed the title
Val is used by and/or.
I would like to file a separate PR for the above commits :) |
dtcxzyw
reviewed
Mar 22, 2024
Done, see: #86302 Once that gets in ill rebase this one (merge conflicts otherwise). |
dtcxzyw
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ping |
… (and/or X, Y))`; NFC
…; NFC `(icmp uge/ugt (and X, Y), C)` implies both `(icmp uge/ugt X, C)` and `(icmp uge/ugt Y, C)`. We can use this to deduce leading ones in `X`. `(icmp ule/ult (or X, Y), C)` implies both `(icmp ule/ult X, C)` and `(icmp ule/ult Y, C)`. We can use this to deduce leading zeros in `X`.
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Yeah I guess an empty diff isn't really all that exciting. For my money, if there is no-compile time impact, its better to have it covered than not, especially since I think there will end up being minimal code complexity added since the |
dtcxzyw
approved these changes
Apr 10, 2024
|
@nikic, going to push this unless you have any objections. |
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(icmp upred X (and/or X, Y)); NFC(icmp upred X (and/or X, Y)); NFCProofs: https://alive2.llvm.org/ce/z/K4vFn-