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veera-sivarajanveera-sivarajan
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[CVP] Infer nuw/nsw Flags for TruncInst
IPSCCP can do this transform but it does not help the motivating issue since it runs only once early in the optimization pipeline. Reimplementing this in CVP folds the motivating issue into a simple `icmp eq` instruction.
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6 files changed

+46
-15
lines changed

6 files changed

+46
-15
lines changed

‎llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp‎

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1212,6 +1212,34 @@ static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
12121212
return true;
12131213
}
12141214

1215+
static bool processTrunc(TruncInst *TI, LazyValueInfo *LVI) {
1216+
if (TI->hasNoSignedWrap() && TI->hasNoUnsignedWrap())
1217+
return false;
1218+
1219+
ConstantRange Range =
1220+
LVI->getConstantRangeAtUse(TI->getOperandUse(0), /*UndefAllowed=*/false);
1221+
uint64_t DestWidth = TI->getDestTy()->getScalarSizeInBits();
1222+
bool Changed = false;
1223+
1224+
if (!TI->hasNoUnsignedWrap()) {
1225+
if (Range.getActiveBits() <= DestWidth) {
1226+
TI->setHasNoUnsignedWrap(true);
1227+
++NumNUW;
1228+
Changed = true;
1229+
}
1230+
}
1231+
1232+
if (!TI->hasNoSignedWrap()) {
1233+
if (Range.getMinSignedBits() <= DestWidth) {
1234+
TI->setHasNoSignedWrap(true);
1235+
++NumNSW;
1236+
Changed = true;
1237+
}
1238+
}
1239+
1240+
return Changed;
1241+
}
1242+
12151243
static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
12161244
const SimplifyQuery &SQ) {
12171245
bool FnChanged = false;
@@ -1275,6 +1303,9 @@ static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
12751303
case Instruction::And:
12761304
BBChanged |= processAnd(cast<BinaryOperator>(&II), LVI);
12771305
break;
1306+
case Instruction::Trunc:
1307+
BBChanged |= processTrunc(cast<TruncInst>(&II), LVI);
1308+
break;
12781309
}
12791310
}
12801311

‎llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -339,7 +339,7 @@ define i1 @test12(i32 %x) {
339339
; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X:%.*]] to i64
340340
; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i64 [[ZEXT]], 7
341341
; CHECK-NEXT: [[SHR:%.*]] = lshr i64 [[MUL]], 32
342-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i64 [[SHR]] to i32
342+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i64 [[SHR]] to i32
343343
; CHECK-NEXT: ret i1 true
344344
;
345345
%zext = zext i32 %x to i64

‎llvm/test/Transforms/CorrelatedValuePropagation/range.ll‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -937,7 +937,7 @@ entry:
937937
define i1 @ctlz_with_range_metadata(i16 %x) {
938938
; CHECK-LABEL: @ctlz_with_range_metadata(
939939
; CHECK-NEXT: [[CTLZ:%.*]] = call i16 @llvm.ctlz.i16(i16 [[X:%.*]], i1 false), !range [[RNG5:![0-9]+]]
940-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[CTLZ]] to i8
940+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[CTLZ]] to i8
941941
; CHECK-NEXT: ret i1 true
942942
;
943943
%ctlz = call i16 @llvm.ctlz.i16(i16 %x, i1 false), !range !{i16 0, i16 8}
@@ -949,7 +949,7 @@ define i1 @ctlz_with_range_metadata(i16 %x) {
949949
define i1 @abs_with_range_metadata(i16 %x) {
950950
; CHECK-LABEL: @abs_with_range_metadata(
951951
; CHECK-NEXT: [[ABS:%.*]] = call i16 @llvm.abs.i16(i16 [[X:%.*]], i1 false), !range [[RNG5]]
952-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[ABS]] to i8
952+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[ABS]] to i8
953953
; CHECK-NEXT: ret i1 true
954954
;
955955
%abs = call i16 @llvm.abs.i16(i16 %x, i1 false), !range !{i16 0, i16 8}

‎llvm/test/Transforms/CorrelatedValuePropagation/sext.ll‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@ define void @test1(i32 %n) {
2020
; CHECK: for.body:
2121
; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext nneg i32 [[A]] to i64
2222
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
23-
; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE1]] to i32
23+
; CHECK-NEXT: [[EXT]] = trunc nuw nsw i64 [[EXT_WIDE1]] to i32
2424
; CHECK-NEXT: br label [[FOR_COND]]
2525
; CHECK: for.end:
2626
; CHECK-NEXT: ret void
@@ -55,7 +55,7 @@ define void @test2(i32 %n) {
5555
; CHECK: for.body:
5656
; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[A]] to i64
5757
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
58-
; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
58+
; CHECK-NEXT: [[EXT]] = trunc nsw i64 [[EXT_WIDE]] to i32
5959
; CHECK-NEXT: br label [[FOR_COND]]
6060
; CHECK: for.end:
6161
; CHECK-NEXT: ret void
@@ -87,7 +87,7 @@ define void @test3(i32 %n) {
8787
; CHECK: bb:
8888
; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext nneg i32 [[N]] to i64
8989
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
90-
; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE1]] to i32
90+
; CHECK-NEXT: [[EXT:%.*]] = trunc nuw nsw i64 [[EXT_WIDE1]] to i32
9191
; CHECK-NEXT: br label [[EXIT]]
9292
; CHECK: exit:
9393
; CHECK-NEXT: ret void
@@ -115,7 +115,7 @@ define void @test4(i32 %n) {
115115
; CHECK: bb:
116116
; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[N]] to i64
117117
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
118-
; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
118+
; CHECK-NEXT: [[EXT:%.*]] = trunc nsw i64 [[EXT_WIDE]] to i32
119119
; CHECK-NEXT: br label [[EXIT]]
120120
; CHECK: exit:
121121
; CHECK-NEXT: ret void

‎llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@ define i1 @infer_nuw(i8 range(i8 0, 2) %A, i8 range(i8 0, 2) %B) {
66
; CHECK-LABEL: define i1 @infer_nuw(
77
; CHECK-SAME: i8 range(i8 0, 2) [[A:%.*]], i8 range(i8 0, 2) [[B:%.*]]) {
88
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[B]], [[A]]
9-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[XOR]] to i1
9+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[XOR]] to i1
1010
; CHECK-NEXT: [[RESULT:%.*]] = xor i1 [[TRUNC]], true
1111
; CHECK-NEXT: ret i1 [[RESULT]]
1212
;
@@ -21,7 +21,7 @@ define i4 @infer_nsw(i8 %A) {
2121
; CHECK-LABEL: define range(i4 -4, 4) i4 @infer_nsw(
2222
; CHECK-SAME: i8 [[A:%.*]]) {
2323
; CHECK-NEXT: [[ASHR:%.*]] = ashr i8 [[A]], 5
24-
; CHECK-NEXT: [[B:%.*]] = trunc i8 [[ASHR]] to i4
24+
; CHECK-NEXT: [[B:%.*]] = trunc nsw i8 [[ASHR]] to i4
2525
; CHECK-NEXT: ret i4 [[B]]
2626
;
2727
%ashr = ashr i8 %A, 5
@@ -34,7 +34,7 @@ define i8 @infer_nuw_nsw(i16 range(i16 -5, -3) %A, i16 range(i16 -5, -3) %B) {
3434
; CHECK-LABEL: define range(i8 0, 8) i8 @infer_nuw_nsw(
3535
; CHECK-SAME: i16 range(i16 -5, -3) [[A:%.*]], i16 range(i16 -5, -3) [[B:%.*]]) {
3636
; CHECK-NEXT: [[XOR:%.*]] = xor i16 [[B]], [[A]]
37-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[XOR]] to i8
37+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[XOR]] to i8
3838
; CHECK-NEXT: [[XOR2:%.*]] = xor i8 [[TRUNC]], 1
3939
; CHECK-NEXT: ret i8 [[XOR2]]
4040
;
@@ -59,7 +59,7 @@ define i1 @rust_issue_122734(i8 range(i8 0, 3) %A, i8 range(i8 0, 3) %B) {
5959
; CHECK-NEXT: ret i1 [[PHI]]
6060
; CHECK: [[IFFALSE]]:
6161
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[A]], [[B]]
62-
; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[XOR]] to i1
62+
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[XOR]] to i1
6363
; CHECK-NEXT: [[XOR2]] = xor i1 [[TRUNC]], true
6464
; CHECK-NEXT: br label %[[IFTRUE]]
6565
;

‎llvm/test/Transforms/CorrelatedValuePropagation/zext.ll‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@ define void @test1(i32 %n) {
1414
; CHECK: for.body:
1515
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext nneg i32 [[A]] to i64
1616
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
17-
; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
17+
; CHECK-NEXT: [[EXT]] = trunc nuw nsw i64 [[EXT_WIDE]] to i32
1818
; CHECK-NEXT: br label [[FOR_COND]]
1919
; CHECK: for.end:
2020
; CHECK-NEXT: ret void
@@ -49,7 +49,7 @@ define void @test2(i32 %n) {
4949
; CHECK: for.body:
5050
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext i32 [[A]] to i64
5151
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
52-
; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
52+
; CHECK-NEXT: [[EXT]] = trunc nuw i64 [[EXT_WIDE]] to i32
5353
; CHECK-NEXT: br label [[FOR_COND]]
5454
; CHECK: for.end:
5555
; CHECK-NEXT: ret void
@@ -81,7 +81,7 @@ define void @test3(i32 %n) {
8181
; CHECK: bb:
8282
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext nneg i32 [[N]] to i64
8383
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
84-
; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
84+
; CHECK-NEXT: [[EXT:%.*]] = trunc nuw nsw i64 [[EXT_WIDE]] to i32
8585
; CHECK-NEXT: br label [[EXIT]]
8686
; CHECK: exit:
8787
; CHECK-NEXT: ret void
@@ -109,7 +109,7 @@ define void @test4(i32 %n) {
109109
; CHECK: bb:
110110
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext i32 [[N]] to i64
111111
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
112-
; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
112+
; CHECK-NEXT: [[EXT:%.*]] = trunc nuw i64 [[EXT_WIDE]] to i32
113113
; CHECK-NEXT: br label [[EXIT]]
114114
; CHECK: exit:
115115
; CHECK-NEXT: ret void

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