[clang] 5073b5f - [CVP] Infer `nuw`/`nsw` flags for TruncInst (#130504)
via cfe-commits
cfe-commits at lists.llvm.org
Wed Mar 12 05:25:29 PDT 2025
Author: Veera
Date: 2025-03-12T08:25:24-04:00
New Revision: 5073b5fdfaf90f5d94640cf9031c73d27a91e394
URL: https://github.com/llvm/llvm-project/commit/5073b5fdfaf90f5d94640cf9031c73d27a91e394
DIFF: https://github.com/llvm/llvm-project/commit/5073b5fdfaf90f5d94640cf9031c73d27a91e394.diff
LOG: [CVP] Infer `nuw`/`nsw` flags for TruncInst (#130504)
Proof: https://alive2.llvm.org/ce/z/U-G7yV
Helps: https://github.com/rust-lang/rust/issues/72646 and
https://github.com/rust-lang/rust/issues/122734
Rust compiler's current output: https://godbolt.org/z/7E3fET6Md
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.
Fixes #130100
Added:
llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll
Modified:
clang/test/CodeGen/attr-counted-by.c
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
llvm/test/Transforms/CorrelatedValuePropagation/range.ll
llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
llvm/test/Transforms/CorrelatedValuePropagation/zext.ll
Removed:
################################################################################
diff --git a/clang/test/CodeGen/attr-counted-by.c b/clang/test/CodeGen/attr-counted-by.c
index e85f3db1121af..dfdf06587f0e2 100644
--- a/clang/test/CodeGen/attr-counted-by.c
+++ b/clang/test/CodeGen/attr-counted-by.c
@@ -333,7 +333,7 @@ size_t test3_bdos(struct annotated *p) {
// SANITIZE-WITH-ATTR-NEXT: [[COUNT50:%.*]] = sext i32 [[DOTCOUNTED_BY_LOAD44]] to i64
// SANITIZE-WITH-ATTR-NEXT: [[TMP10:%.*]] = sub nsw i64 [[COUNT50]], [[IDXPROM42]]
// SANITIZE-WITH-ATTR-NEXT: [[TMP11:%.*]] = tail call i64 @llvm.smax.i64(i64 [[TMP10]], i64 0)
-// SANITIZE-WITH-ATTR-NEXT: [[DOTTR:%.*]] = trunc nuw i64 [[TMP11]] to i32
+// SANITIZE-WITH-ATTR-NEXT: [[DOTTR:%.*]] = trunc nuw nsw i64 [[TMP11]] to i32
// SANITIZE-WITH-ATTR-NEXT: [[CONV54:%.*]] = shl i32 [[DOTTR]], 2
// SANITIZE-WITH-ATTR-NEXT: [[CONV55:%.*]] = and i32 [[CONV54]], 252
// SANITIZE-WITH-ATTR-NEXT: store i32 [[CONV55]], ptr [[ARRAYIDX65]], align 4, !tbaa [[TBAA4]]
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 8e74b8645fad9..314a5d15f0f88 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -1212,6 +1212,34 @@ static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
return true;
}
+static bool processTrunc(TruncInst *TI, LazyValueInfo *LVI) {
+ if (TI->hasNoSignedWrap() && TI->hasNoUnsignedWrap())
+ return false;
+
+ ConstantRange Range =
+ LVI->getConstantRangeAtUse(TI->getOperandUse(0), /*UndefAllowed=*/false);
+ uint64_t DestWidth = TI->getDestTy()->getScalarSizeInBits();
+ bool Changed = false;
+
+ if (!TI->hasNoUnsignedWrap()) {
+ if (Range.getActiveBits() <= DestWidth) {
+ TI->setHasNoUnsignedWrap(true);
+ ++NumNUW;
+ Changed = true;
+ }
+ }
+
+ if (!TI->hasNoSignedWrap()) {
+ if (Range.getMinSignedBits() <= DestWidth) {
+ TI->setHasNoSignedWrap(true);
+ ++NumNSW;
+ Changed = true;
+ }
+ }
+
+ return Changed;
+}
+
static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
const SimplifyQuery &SQ) {
bool FnChanged = false;
@@ -1275,6 +1303,9 @@ static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
case Instruction::And:
BBChanged |= processAnd(cast<BinaryOperator>(&II), LVI);
break;
+ case Instruction::Trunc:
+ BBChanged |= processTrunc(cast<TruncInst>(&II), LVI);
+ break;
}
}
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
index 5fa8f4e1b9f29..7fb1e0718795d 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -339,7 +339,7 @@ define i1 @test12(i32 %x) {
; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X:%.*]] to i64
; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i64 [[ZEXT]], 7
; CHECK-NEXT: [[SHR:%.*]] = lshr i64 [[MUL]], 32
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc i64 [[SHR]] to i32
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i64 [[SHR]] to i32
; CHECK-NEXT: ret i1 true
;
%zext = zext i32 %x to i64
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/range.ll b/llvm/test/Transforms/CorrelatedValuePropagation/range.ll
index 03d71fa9b5277..caf1156d79229 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/range.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/range.ll
@@ -937,7 +937,7 @@ entry:
define i1 @ctlz_with_range_metadata(i16 %x) {
; CHECK-LABEL: @ctlz_with_range_metadata(
; CHECK-NEXT: [[CTLZ:%.*]] = call i16 @llvm.ctlz.i16(i16 [[X:%.*]], i1 false), !range [[RNG5:![0-9]+]]
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[CTLZ]] to i8
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[CTLZ]] to i8
; CHECK-NEXT: ret i1 true
;
%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) {
define i1 @abs_with_range_metadata(i16 %x) {
; CHECK-LABEL: @abs_with_range_metadata(
; CHECK-NEXT: [[ABS:%.*]] = call i16 @llvm.abs.i16(i16 [[X:%.*]], i1 false), !range [[RNG5]]
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc i16 [[ABS]] to i8
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[ABS]] to i8
; CHECK-NEXT: ret i1 true
;
%abs = call i16 @llvm.abs.i16(i16 %x, i1 false), !range !{i16 0, i16 8}
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/sext.ll b/llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
index 0db520bfc68a2..648ef0864bf17 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/sext.ll
@@ -20,7 +20,7 @@ define void @test1(i32 %n) {
; CHECK: for.body:
; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext nneg i32 [[A]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
-; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE1]] to i32
+; CHECK-NEXT: [[EXT]] = trunc nuw nsw i64 [[EXT_WIDE1]] to i32
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@@ -55,7 +55,7 @@ define void @test2(i32 %n) {
; CHECK: for.body:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[A]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT]] = trunc nsw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@@ -87,7 +87,7 @@ define void @test3(i32 %n) {
; CHECK: bb:
; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext nneg i32 [[N]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
-; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE1]] to i32
+; CHECK-NEXT: [[EXT:%.*]] = trunc nuw nsw i64 [[EXT_WIDE1]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
@@ -115,7 +115,7 @@ define void @test4(i32 %n) {
; CHECK: bb:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[N]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT:%.*]] = trunc nsw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll b/llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll
new file mode 100644
index 0000000000000..9b6604298840d
--- /dev/null
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/trunc.ll
@@ -0,0 +1,108 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
+
+
+define i1 @infer_nuw(i8 range(i8 0, 2) %A, i8 range(i8 0, 2) %B) {
+; CHECK-LABEL: define i1 @infer_nuw(
+; CHECK-SAME: i8 range(i8 0, 2) [[A:%.*]], i8 range(i8 0, 2) [[B:%.*]]) {
+; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[B]], [[A]]
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[XOR]] to i1
+; CHECK-NEXT: ret i1 [[TRUNC]]
+;
+ %xor = xor i8 %B, %A
+ %trunc = trunc i8 %xor to i1
+ ret i1 %trunc
+}
+
+
+define i4 @infer_nsw(i8 %A) {
+; CHECK-LABEL: define range(i4 -4, 4) i4 @infer_nsw(
+; CHECK-SAME: i8 [[A:%.*]]) {
+; CHECK-NEXT: [[ASHR:%.*]] = ashr i8 [[A]], 5
+; CHECK-NEXT: [[B:%.*]] = trunc nsw i8 [[ASHR]] to i4
+; CHECK-NEXT: ret i4 [[B]]
+;
+ %ashr = ashr i8 %A, 5
+ %result = trunc i8 %ashr to i4
+ ret i4 %result
+}
+
+
+define i8 @infer_nuw_nsw(i16 range(i16 -5, -3) %A, i16 range(i16 -5, -3) %B) {
+; CHECK-LABEL: define range(i8 0, 8) i8 @infer_nuw_nsw(
+; CHECK-SAME: i16 range(i16 -5, -3) [[A:%.*]], i16 range(i16 -5, -3) [[B:%.*]]) {
+; CHECK-NEXT: [[XOR:%.*]] = xor i16 [[B]], [[A]]
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw nsw i16 [[XOR]] to i8
+; CHECK-NEXT: ret i8 [[TRUNC]]
+;
+ %xor = xor i16 %B, %A
+ %trunc = trunc i16 %xor to i8
+ ret i8 %trunc
+}
+
+
+define i8 @infer_nsw_from_assume(i16 %x) {
+; CHECK-LABEL: define i8 @infer_nsw_from_assume(
+; CHECK-SAME: i16 [[X:%.*]]) {
+; CHECK-NEXT: [[ADD:%.*]] = add i16 [[X]], 128
+; CHECK-NEXT: [[OR_COND_I:%.*]] = icmp ult i16 [[ADD]], 256
+; CHECK-NEXT: tail call void @llvm.assume(i1 [[OR_COND_I]])
+; CHECK-NEXT: [[CONV1:%.*]] = trunc nsw i16 [[X]] to i8
+; CHECK-NEXT: ret i8 [[CONV1]]
+;
+ %add = add i16 %x, 128
+ %or.cond.i = icmp ult i16 %add, 256
+ tail call void @llvm.assume(i1 %or.cond.i)
+ %conv1 = trunc i16 %x to i8
+ ret i8 %conv1
+}
+
+
+define i1 @rust_issue_122734(i8 range(i8 0, 3) %A, i8 range(i8 0, 3) %B) {
+; CHECK-LABEL: define i1 @rust_issue_122734(
+; CHECK-SAME: i8 range(i8 0, 3) [[A:%.*]], i8 range(i8 0, 3) [[B:%.*]]) {
+; CHECK-NEXT: [[START:.*]]:
+; CHECK-NEXT: [[LHS:%.*]] = icmp eq i8 [[A]], 2
+; CHECK-NEXT: [[RHS:%.*]] = icmp eq i8 [[B]], 2
+; CHECK-NEXT: [[OR:%.*]] = or i1 [[LHS]], [[RHS]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[LHS]], [[RHS]]
+; CHECK-NEXT: br i1 [[OR]], label %[[IFTRUE:.*]], label %[[IFFALSE:.*]]
+; CHECK: [[IFTRUE]]:
+; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[XOR2:%.*]], %[[IFFALSE]] ], [ [[AND]], %[[START]] ]
+; CHECK-NEXT: ret i1 [[PHI]]
+; CHECK: [[IFFALSE]]:
+; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[A]], [[B]]
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[XOR]] to i1
+; CHECK-NEXT: [[XOR2]] = xor i1 [[TRUNC]], true
+; CHECK-NEXT: br label %[[IFTRUE]]
+;
+start:
+ %lhs = icmp eq i8 %A, 2
+ %rhs = icmp eq i8 %B, 2
+ %or = or i1 %lhs, %rhs
+ %and = and i1 %lhs, %rhs
+ br i1 %or, label %iftrue, label %iffalse
+
+iftrue:
+ %phi = phi i1 [ %xor2, %iffalse], [ %and, %start ]
+ ret i1 %phi
+
+iffalse:
+ %xor = xor i8 %A, %B
+ %trunc = trunc i8 %xor to i1
+ %xor2 = xor i1 %trunc, true
+ br label %iftrue
+}
+
+
+define i1 @overdefined_range_negative(i8 %A, i8 %B) {
+; CHECK-LABEL: define i1 @overdefined_range_negative(
+; CHECK-SAME: i8 [[A:%.*]], i8 [[B:%.*]]) {
+; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[A]], [[B]]
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[XOR]] to i1
+; CHECK-NEXT: ret i1 [[TRUNC]]
+;
+ %xor = xor i8 %A, %B
+ %trunc = trunc i8 %xor to i1
+ ret i1 %trunc
+}
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/zext.ll b/llvm/test/Transforms/CorrelatedValuePropagation/zext.ll
index 44434c696fe37..8e43244a8eb62 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/zext.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/zext.ll
@@ -14,7 +14,7 @@ define void @test1(i32 %n) {
; CHECK: for.body:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext nneg i32 [[A]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT]] = trunc nuw nsw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@@ -49,7 +49,7 @@ define void @test2(i32 %n) {
; CHECK: for.body:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext i32 [[A]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT]] = trunc nuw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@@ -81,7 +81,7 @@ define void @test3(i32 %n) {
; CHECK: bb:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext nneg i32 [[N]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT:%.*]] = trunc nuw nsw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
@@ -109,7 +109,7 @@ define void @test4(i32 %n) {
; CHECK: bb:
; CHECK-NEXT: [[EXT_WIDE:%.*]] = zext i32 [[N]] to i64
; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
-; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT: [[EXT:%.*]] = trunc nuw i64 [[EXT_WIDE]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
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