Add nuw flag when possible

Author: YanWQ-monad

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

@@ -310,6 +310,15 @@ static bool processEqualityICmp(ICmpInst *Cmp, LazyValueInfo *LVI) {
   if ((*RHSC)[0] == ShouldBeOdd) {
     IRBuilder<> B{Cmp};
     Value *Trunc = B.CreateTrunc(Op0, Cmp->getType());
+    if (auto *I = dyn_cast<TruncInst>(Trunc)) {
+      // if Range == [0, 1], i.e. the value is already valid boolean
+      if (Range.getLower() == 0)
+        I->setHasNoUnsignedWrap(true);
+      // if Range == [-1, 0]
+      if (Range.getUpper() == 1)
+        I->setHasNoSignedWrap(true);
+    }
+
     Cmp->replaceAllUsesWith(Trunc);
     Cmp->eraseFromParent();
     return true;

llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll

@@ -614,7 +614,7 @@ define void @test_cmp_phi(i8 %a) {
 ; CHECK-NEXT:    br i1 [[C0]], label [[LOOP:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[P:%.*]] = phi i8 [ [[A]], [[ENTRY:%.*]] ], [ [[B:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[TMP0:%.*]] = trunc i8 [[P]] to i1
+; CHECK-NEXT:    [[TMP0:%.*]] = trunc nuw i8 [[P]] to i1
 ; CHECK-NEXT:    [[C4:%.*]] = call i1 @get_bool()
 ; CHECK-NEXT:    [[B]] = zext i1 [[C4]] to i8
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[LOOP]], label [[EXIT]]
@@ -1484,7 +1484,7 @@ define i1 @test_icmp_eq_on_valid_bool_range(i8 %x) {
 ; CHECK-NEXT:    [[TMP2:%.*]] = tail call i1 @get_bool()
 ; CHECK-NEXT:    br label [[BB3:%.*]]
 ; CHECK:       bb1:
-; CHECK-NEXT:    [[TMP3:%.*]] = trunc i8 [[X]] to i1
+; CHECK-NEXT:    [[TMP3:%.*]] = trunc nuw i8 [[X]] to i1
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[TMP4:%.*]] = phi i1 [ [[TMP3]], [[BB1]] ], [ [[TMP2]], [[BB2]] ]
@@ -1514,7 +1514,7 @@ define i1 @test_icmp_ne_on_valid_bool_range(i8 %x) {
 ; CHECK-NEXT:    [[TMP2:%.*]] = tail call i1 @get_bool()
 ; CHECK-NEXT:    br label [[BB3:%.*]]
 ; CHECK:       bb1:
-; CHECK-NEXT:    [[TMP3:%.*]] = trunc i8 [[X]] to i1
+; CHECK-NEXT:    [[TMP3:%.*]] = trunc nuw i8 [[X]] to i1
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[TMP4:%.*]] = phi i1 [ [[TMP3]], [[BB1]] ], [ [[TMP2]], [[BB2]] ]
@@ -1580,7 +1580,7 @@ define i1 @test_icmp_ne_on_nsw(i8 %x) {
 ; CHECK-NEXT:    [[TMP4:%.*]] = tail call i1 @get_bool()
 ; CHECK-NEXT:    br label [[BB3:%.*]]
 ; CHECK:       bb1:
-; CHECK-NEXT:    [[TMP5:%.*]] = trunc i8 [[X]] to i1
+; CHECK-NEXT:    [[TMP5:%.*]] = trunc nsw i8 [[X]] to i1
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[TMP6:%.*]] = phi i1 [ [[TMP5]], [[BB1]] ], [ [[TMP4]], [[BB2]] ]

llvm/test/Transforms/JumpThreading/pr33917.ll

@@ -23,7 +23,7 @@ define void @patatino() personality ptr @rust_eh_personality {
 ; CHECK:       good:
 ; CHECK-NEXT:    [[T11:%.*]] = icmp ne ptr [[T9]], null
 ; CHECK-NEXT:    [[T12:%.*]] = zext i1 [[T11]] to i64
-; CHECK-NEXT:    [[TMP0:%.*]] = trunc i64 [[T12]] to i1
+; CHECK-NEXT:    [[TMP0:%.*]] = trunc nuw i64 [[T12]] to i1
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[IF_TRUE:%.*]], label [[DONE:%.*]]
 ; CHECK:       if_true:
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[T11]])