[llvm] perf/goldsteinn/improve smax (PR #88170)
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Tue Apr 9 10:57:08 PDT 2024
https://github.com/goldsteinn created https://github.com/llvm/llvm-project/pull/88170
- **[ValueTracking] Expand `isKnown{Negative,Positive}` APIs; NFC**
- **[ValueTracking] Add tests for improving `isKnownNonZero` of `smax`; NFC**
- **[ValueTracking] improve `isKnownNonZero` precision for `smax`**
>From 2bbbf152d862ac0ab3e29abe924e7acd2ce884dd Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Tue, 9 Apr 2024 11:54:22 -0500
Subject: [PATCH 1/3] [ValueTracking] Expand `isKnown{Negative,Positive}` APIs;
NFC
1) Add support for `DemandedElts`.
2) Add private API that also returns the already computed KnownBits.
---
llvm/include/llvm/Analysis/ValueTracking.h | 10 ++++++
llvm/lib/Analysis/ValueTracking.cpp | 41 +++++++++++++++++++---
2 files changed, 46 insertions(+), 5 deletions(-)
diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h
index 3970efba18cc8c..7287a8fb122bbb 100644
--- a/llvm/include/llvm/Analysis/ValueTracking.h
+++ b/llvm/include/llvm/Analysis/ValueTracking.h
@@ -145,11 +145,21 @@ bool isKnownNonNegative(const Value *V, const SimplifyQuery &SQ,
bool isKnownPositive(const Value *V, const SimplifyQuery &SQ,
unsigned Depth = 0);
+/// Returns true if the given value is known be positive (i.e. non-negative
+/// and non-zero) for DemandedElts.
+bool isKnownPositive(const Value *V, const APInt &DemandedElts,
+ const SimplifyQuery &SQ, unsigned Depth = 0);
+
/// Returns true if the given value is known be negative (i.e. non-positive
/// and non-zero).
bool isKnownNegative(const Value *V, const SimplifyQuery &DL,
unsigned Depth = 0);
+/// Returns true if the given value is known be negative (i.e. non-positive
+/// and non-zero) for DemandedElts.
+bool isKnownNegative(const Value *V, const APInt &DemandedElts,
+ const SimplifyQuery &DL, unsigned Depth = 0);
+
/// Return true if the given values are known to be non-equal when defined.
/// Supports scalar integer types only.
bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL,
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index ca48cfe7738154..3bc5d9ee193f79 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -289,21 +289,52 @@ bool llvm::isKnownNonNegative(const Value *V, const SimplifyQuery &SQ,
return computeKnownBits(V, Depth, SQ).isNonNegative();
}
-bool llvm::isKnownPositive(const Value *V, const SimplifyQuery &SQ,
- unsigned Depth) {
+static bool isKnownPositive(const Value *V, const APInt &DemandedElts,
+ KnownBits &Known, const SimplifyQuery &SQ,
+ unsigned Depth) {
if (auto *CI = dyn_cast<ConstantInt>(V))
return CI->getValue().isStrictlyPositive();
// If `isKnownNonNegative` ever becomes more sophisticated, make sure to keep
// this updated.
- KnownBits Known = computeKnownBits(V, Depth, SQ);
+ Known = computeKnownBits(V, DemandedElts, Depth, SQ);
return Known.isNonNegative() &&
- (Known.isNonZero() || ::isKnownNonZero(V, Depth, SQ));
+ (Known.isNonZero() || ::isKnownNonZero(V, DemandedElts, Depth, SQ));
+}
+
+bool llvm::isKnownPositive(const Value *V, const APInt &DemandedElts,
+ const SimplifyQuery &SQ, unsigned Depth) {
+ KnownBits Known(getBitWidth(V->getType(), SQ.DL));
+ return ::isKnownPositive(V, DemandedElts, Known, SQ, Depth);
+}
+
+bool llvm::isKnownPositive(const Value *V, const SimplifyQuery &SQ,
+ unsigned Depth) {
+ auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
+ APInt DemandedElts =
+ FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
+ return isKnownPositive(V, DemandedElts, SQ, Depth);
+}
+
+static bool isKnownNegative(const Value *V, const APInt &DemandedElts,
+ KnownBits &Known, const SimplifyQuery &SQ,
+ unsigned Depth) {
+ Known = computeKnownBits(V, DemandedElts, Depth, SQ);
+ return Known.isNegative();
+}
+
+bool llvm::isKnownNegative(const Value *V, const APInt &DemandedElts,
+ const SimplifyQuery &SQ, unsigned Depth) {
+ KnownBits Known(getBitWidth(V->getType(), SQ.DL));
+ return ::isKnownNegative(V, DemandedElts, Known, SQ, Depth);
}
bool llvm::isKnownNegative(const Value *V, const SimplifyQuery &SQ,
unsigned Depth) {
- return computeKnownBits(V, Depth, SQ).isNegative();
+ auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
+ APInt DemandedElts =
+ FVTy ? APInt::getAllOnes(FVTy->getNumElements()) : APInt(1, 1);
+ return isKnownNegative(V, DemandedElts, SQ, Depth);
}
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
>From 0b65ee4774678681340f3e4dc7d57179840008f2 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Tue, 9 Apr 2024 12:36:03 -0500
Subject: [PATCH 2/3] [ValueTracking] Add tests for improving `isKnownNonZero`
of `smax`; NFC
---
.../Transforms/InstSimplify/known-non-zero.ll | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/llvm/test/Transforms/InstSimplify/known-non-zero.ll b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
index b647f11af4461d..6ebc4e0f31a9cf 100644
--- a/llvm/test/Transforms/InstSimplify/known-non-zero.ll
+++ b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
@@ -166,3 +166,18 @@ A:
B:
ret i1 0
}
+
+define i1 @smax_non_zero(i8 %xx, i8 %y) {
+; CHECK-LABEL: @smax_non_zero(
+; CHECK-NEXT: [[X0:%.*]] = and i8 [[XX:%.*]], 63
+; CHECK-NEXT: [[X:%.*]] = add i8 [[X0]], 1
+; CHECK-NEXT: [[V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 [[Y:%.*]])
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[V]], 0
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %x0 = and i8 %xx, 63
+ %x = add i8 %x0, 1
+ %v = call i8 @llvm.smax.i8(i8 %x, i8 %y)
+ %r = icmp eq i8 %v, 0
+ ret i1 %r
+}
>From 346e682ad4dbebd1483511467291796f585d0a14 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n at gmail.com>
Date: Tue, 9 Apr 2024 11:58:03 -0500
Subject: [PATCH 3/3] [ValueTracking] improve `isKnownNonZero` precision for
`smax`
Instead of relying on known-bits for strictly positive, use the
`isKnownPositive` API. This will use `isKnownNonZero` which is more
accurate.
---
llvm/lib/Analysis/ValueTracking.cpp | 25 ++++++++-----------
.../Transforms/InstSimplify/known-non-zero.ll | 6 +----
2 files changed, 12 insertions(+), 19 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 3bc5d9ee193f79..187d781c59e072 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2861,21 +2861,18 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
isKnownNonZero(II->getArgOperand(0), DemandedElts, Depth, Q);
case Intrinsic::smin:
case Intrinsic::smax: {
- auto KnownOpImpliesNonZero = [&](const KnownBits &K) {
- return II->getIntrinsicID() == Intrinsic::smin
- ? K.isNegative()
- : K.isStrictlyPositive();
+ bool AllNonZero = true;
+ auto KnownOpImpliesNonZero = [&](const Value *Op) {
+ KnownBits TmpKnown(getBitWidth(Op->getType(), Q.DL));
+ bool Ret =
+ II->getIntrinsicID() == Intrinsic::smin
+ ? ::isKnownNegative(Op, DemandedElts, TmpKnown, Q, Depth)
+ : ::isKnownPositive(Op, DemandedElts, TmpKnown, Q, Depth);
+ AllNonZero &= TmpKnown.isNonZero();
+ return Ret;
};
- KnownBits XKnown =
- computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q);
- if (KnownOpImpliesNonZero(XKnown))
- return true;
- KnownBits YKnown =
- computeKnownBits(II->getArgOperand(1), DemandedElts, Depth, Q);
- if (KnownOpImpliesNonZero(YKnown))
- return true;
-
- if (XKnown.isNonZero() && YKnown.isNonZero())
+ if (KnownOpImpliesNonZero(II->getArgOperand(0)) ||
+ KnownOpImpliesNonZero(II->getArgOperand(1)) || AllNonZero)
return true;
}
[[fallthrough]];
diff --git a/llvm/test/Transforms/InstSimplify/known-non-zero.ll b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
index 6ebc4e0f31a9cf..51f80f62c2f34c 100644
--- a/llvm/test/Transforms/InstSimplify/known-non-zero.ll
+++ b/llvm/test/Transforms/InstSimplify/known-non-zero.ll
@@ -169,11 +169,7 @@ B:
define i1 @smax_non_zero(i8 %xx, i8 %y) {
; CHECK-LABEL: @smax_non_zero(
-; CHECK-NEXT: [[X0:%.*]] = and i8 [[XX:%.*]], 63
-; CHECK-NEXT: [[X:%.*]] = add i8 [[X0]], 1
-; CHECK-NEXT: [[V:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 [[Y:%.*]])
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[V]], 0
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%x0 = and i8 %xx, 63
%x = add i8 %x0, 1
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