[llvm] 402dfa3 - [ValueTracking] Support vscale in computeConstantRange()
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 17 02:05:30 PDT 2023
Author: Nikita Popov
Date: 2023-03-17T10:03:24+01:00
New Revision: 402dfa389e136c75ac7f341ea85ff4c854aa0e93
URL: https://github.com/llvm/llvm-project/commit/402dfa389e136c75ac7f341ea85ff4c854aa0e93
DIFF: https://github.com/llvm/llvm-project/commit/402dfa389e136c75ac7f341ea85ff4c854aa0e93.diff
LOG: [ValueTracking] Support vscale in computeConstantRange()
Add support for vscale in computeConstantRange(), based on
vscale_range attributes. This allows simplifying based on the
precise range, rather than a KnownBits approximation (which will
be off by a factor of two for the usual case of a power of two
upper bound).
Differential Revision: https://reviews.llvm.org/D146217
Added:
Modified:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Transforms/InstCombine/icmp-vscale.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index cfa9b1b0fc6b7..6cc2fb2ebcc24 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1152,6 +1152,25 @@ KnownBits llvm::analyzeKnownBitsFromAndXorOr(
Query(DL, AC, safeCxtI(I, CxtI), DT, UseInstrInfo, ORE));
}
+static ConstantRange getVScaleRange(const Function *F, unsigned BitWidth) {
+ Attribute Attr = F->getFnAttribute(Attribute::VScaleRange);
+ // Without vscale_range, we only know that vscale is non-zero.
+ if (!Attr.isValid())
+ return ConstantRange(APInt(BitWidth, 1), APInt::getZero(BitWidth));
+
+ unsigned AttrMin = Attr.getVScaleRangeMin();
+ // Minimum is larger than vscale width, result is always poison.
+ if ((unsigned)llvm::bit_width(AttrMin) > BitWidth)
+ return ConstantRange::getEmpty(BitWidth);
+
+ APInt Min(BitWidth, AttrMin);
+ std::optional<unsigned> AttrMax = Attr.getVScaleRangeMax();
+ if (!AttrMax || (unsigned)llvm::bit_width(*AttrMax) > BitWidth)
+ return ConstantRange(Min, APInt::getZero(BitWidth));
+
+ return ConstantRange(Min, APInt(BitWidth, *AttrMax) + 1);
+}
+
static void computeKnownBitsFromOperator(const Operator *I,
const APInt &DemandedElts,
KnownBits &Known, unsigned Depth,
@@ -1820,31 +1839,10 @@ static void computeKnownBitsFromOperator(const Operator *I,
Known.Zero.setBitsFrom(17);
break;
case Intrinsic::vscale: {
- if (!II->getParent() || !II->getFunction() ||
- !II->getFunction()->hasFnAttribute(Attribute::VScaleRange))
- break;
-
- auto Attr = II->getFunction()->getFnAttribute(Attribute::VScaleRange);
- std::optional<unsigned> VScaleMax = Attr.getVScaleRangeMax();
-
- if (!VScaleMax)
+ if (!II->getParent() || !II->getFunction())
break;
- unsigned VScaleMin = Attr.getVScaleRangeMin();
-
- // If vscale min = max then we know the exact value at compile time
- // and hence we know the exact bits.
- if (VScaleMin == VScaleMax) {
- Known.One = VScaleMin;
- Known.Zero = VScaleMin;
- Known.Zero.flipAllBits();
- break;
- }
-
- unsigned FirstZeroHighBit = llvm::bit_width(*VScaleMax);
- if (FirstZeroHighBit < BitWidth)
- Known.Zero.setBitsFrom(FirstZeroHighBit);
-
+ Known = getVScaleRange(II->getFunction(), BitWidth).toKnownBits();
break;
}
}
@@ -7773,6 +7771,10 @@ static ConstantRange getRangeForIntrinsic(const IntrinsicInst &II) {
return ConstantRange(APInt::getZero(Width),
APInt::getSignedMinValue(Width) + 1);
+ case Intrinsic::vscale:
+ if (!II.getParent() || !II.getFunction())
+ break;
+ return getVScaleRange(II.getFunction(), Width);
default:
break;
}
diff --git a/llvm/test/Transforms/InstCombine/icmp-vscale.ll b/llvm/test/Transforms/InstCombine/icmp-vscale.ll
index 83264ccd3c762..baac5ce495985 100644
--- a/llvm/test/Transforms/InstCombine/icmp-vscale.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-vscale.ll
@@ -84,9 +84,7 @@ entry:
define i1 @vscale_ule_max() vscale_range(5,10) {
; CHECK-LABEL: @vscale_ule_max(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i16 @llvm.vscale.i16()
-; CHECK-NEXT: [[RES:%.*]] = icmp ult i16 [[VSCALE]], 11
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i16 @llvm.vscale.i16()
%res = icmp ule i16 %vscale, 10
@@ -106,9 +104,7 @@ define i1 @vscale_ult_max() vscale_range(5,10) {
define i1 @vscale_uge_min() vscale_range(5,10) {
; CHECK-LABEL: @vscale_uge_min(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i16 @llvm.vscale.i16()
-; CHECK-NEXT: [[RES:%.*]] = icmp ugt i16 [[VSCALE]], 4
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i16 @llvm.vscale.i16()
%res = icmp uge i16 %vscale, 5
@@ -146,9 +142,7 @@ define i1 @vscale_ugt_no_max() vscale_range(5) {
define i1 @vscale_uge_max_overflow() vscale_range(5,256) {
; CHECK-LABEL: @vscale_uge_max_overflow(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i8 @llvm.vscale.i8()
-; CHECK-NEXT: [[RES:%.*]] = icmp ugt i8 [[VSCALE]], 4
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i8 @llvm.vscale.i8()
%res = icmp uge i8 %vscale, 5
@@ -168,9 +162,7 @@ define i1 @vscale_ugt_max_overflow() vscale_range(5,256) {
define i1 @vscale_eq_min_overflow() vscale_range(256,300) {
; CHECK-LABEL: @vscale_eq_min_overflow(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i8 @llvm.vscale.i8()
-; CHECK-NEXT: [[RES:%.*]] = icmp eq i8 [[VSCALE]], 42
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i8 @llvm.vscale.i8()
%res = icmp eq i8 %vscale, 42
@@ -179,9 +171,7 @@ define i1 @vscale_eq_min_overflow() vscale_range(256,300) {
define i1 @vscale_ult_min_overflow() vscale_range(256,300) {
; CHECK-LABEL: @vscale_ult_min_overflow(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i8 @llvm.vscale.i8()
-; CHECK-NEXT: [[RES:%.*]] = icmp ult i8 [[VSCALE]], 42
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i8 @llvm.vscale.i8()
%res = icmp ult i8 %vscale, 42
@@ -190,12 +180,10 @@ define i1 @vscale_ult_min_overflow() vscale_range(256,300) {
define i1 @vscale_ugt_min_overflow() vscale_range(256,300) {
; CHECK-LABEL: @vscale_ugt_min_overflow(
-; CHECK-NEXT: [[VSCALE:%.*]] = call i8 @llvm.vscale.i8()
-; CHECK-NEXT: [[RES:%.*]] = icmp ult i8 [[VSCALE]], 42
-; CHECK-NEXT: ret i1 [[RES]]
+; CHECK-NEXT: ret i1 true
;
%vscale = call i8 @llvm.vscale.i8()
- %res = icmp ult i8 %vscale, 42
+ %res = icmp ugt i8 %vscale, 42
ret i1 %res
}
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