From b8a512b6c40f1b188b8a299dc2d20088e7426183 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403@hotmail.com>
Date: Mon, 11 Aug 2025 12:31:33 +0200
Subject: [PATCH 1/2] [SCCP] Add test for trunc nuw range (NFC).

---
 .../test/Transforms/SCCP/conditions-ranges.ll | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/llvm/test/Transforms/SCCP/conditions-ranges.ll b/llvm/test/Transforms/SCCP/conditions-ranges.ll
index 7a64778b60789..6d88a2a1639b3 100644
--- a/llvm/test/Transforms/SCCP/conditions-ranges.ll
+++ b/llvm/test/Transforms/SCCP/conditions-ranges.ll
@@ -1436,6 +1436,48 @@ if.end:
   ret i32 0
 }
 
+define void @trunc_nuw_i1_dominating_icmp_ne_0(i8 %x) {
+; CHECK-LABEL: @trunc_nuw_i1_dominating_icmp_ne_0(
+; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i8 [[X:%.*]], 0
+; CHECK-NEXT:    br i1 [[ICMP]], label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[C1:%.*]] = trunc nuw i8 [[X]] to i1
+; CHECK-NEXT:    call void @use(i1 [[C1]])
+; CHECK-NEXT:    ret void
+; CHECK:       bb2:
+; CHECK-NEXT:    ret void
+;
+  %icmp = icmp ne i8 %x, 0
+  br i1 %icmp, label %bb1, label %bb2
+bb1:
+  %c1 = trunc nuw i8 %x to i1
+  call void @use(i1 %c1)
+  ret void
+bb2:
+  ret void
+}
+
+define void @neg_trunc_i1_dominating_icmp_ne_0(i8 %x) {
+; CHECK-LABEL: @neg_trunc_i1_dominating_icmp_ne_0(
+; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i8 [[X:%.*]], 0
+; CHECK-NEXT:    br i1 [[ICMP]], label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[C1:%.*]] = trunc i8 [[X]] to i1
+; CHECK-NEXT:    call void @use(i1 [[C1]])
+; CHECK-NEXT:    ret void
+; CHECK:       bb2:
+; CHECK-NEXT:    ret void
+;
+  %icmp = icmp ne i8 %x, 0
+  br i1 %icmp, label %bb1, label %bb2
+bb1:
+  %c1 = trunc i8 %x to i1
+  call void @use(i1 %c1)
+  ret void
+bb2:
+  ret void
+}
+
 define i1 @ptr_icmp_data_layout() {
 ; CHECK-LABEL: @ptr_icmp_data_layout(
 ; CHECK-NEXT:    ret i1 false

From d5cd785aaa31108747fa6debb03b6da7eb74612a Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403@hotmail.com>
Date: Mon, 11 Aug 2025 12:32:53 +0200
Subject: [PATCH 2/2] [SCCP] Add support for trunc nuw range.

---
 llvm/lib/Transforms/Utils/SCCPSolver.cpp       | 8 ++++++--
 llvm/test/Transforms/SCCP/conditions-ranges.ll | 3 +--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index acb9911e8a522..84485176ad4ff 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -1442,8 +1442,12 @@ void SCCPInstVisitor::visitCastInst(CastInst &I) {
         OpSt.asConstantRange(I.getSrcTy(), /*UndefAllowed=*/false);
 
     Type *DestTy = I.getDestTy();
-    ConstantRange Res =
-        OpRange.castOp(I.getOpcode(), DestTy->getScalarSizeInBits());
+    ConstantRange Res = ConstantRange::getEmpty(DestTy->getScalarSizeInBits());
+    if (auto *Trunc = dyn_cast<TruncInst>(&I))
+      Res = OpRange.truncate(DestTy->getScalarSizeInBits(),
+                             Trunc->getNoWrapKind());
+    else
+      Res = OpRange.castOp(I.getOpcode(), DestTy->getScalarSizeInBits());
     mergeInValue(LV, &I, ValueLatticeElement::getRange(Res));
   } else
     markOverdefined(&I);
diff --git a/llvm/test/Transforms/SCCP/conditions-ranges.ll b/llvm/test/Transforms/SCCP/conditions-ranges.ll
index 6d88a2a1639b3..a3cf23bd3ae9a 100644
--- a/llvm/test/Transforms/SCCP/conditions-ranges.ll
+++ b/llvm/test/Transforms/SCCP/conditions-ranges.ll
@@ -1441,8 +1441,7 @@ define void @trunc_nuw_i1_dominating_icmp_ne_0(i8 %x) {
 ; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i8 [[X:%.*]], 0
 ; CHECK-NEXT:    br i1 [[ICMP]], label [[BB1:%.*]], label [[BB2:%.*]]
 ; CHECK:       bb1:
-; CHECK-NEXT:    [[C1:%.*]] = trunc nuw i8 [[X]] to i1
-; CHECK-NEXT:    call void @use(i1 [[C1]])
+; CHECK-NEXT:    call void @use(i1 true)
 ; CHECK-NEXT:    ret void
 ; CHECK:       bb2:
 ; CHECK-NEXT:    ret void