[IR] Fix crashes caused by #85592

[elhewaty]

This patch fixes the crash caused by the pull request:
#85592

[llvmbot]

@llvm/pr-subscribers-llvm-ir

@llvm/pr-subscribers-llvm-transforms

Author: None (elhewaty)

Changes

This patch fixes the crash caused by pull request: https://github.com/llvm/llvm-project/pull/85592

---

Full diff: https://github.com/llvm/llvm-project/pull/87169.diff

2 Files Affected:

• (modified) llvm/lib/IR/Operator.cpp (+3-2)
• (modified) llvm/test/Transforms/FunctionAttrs/noundef.ll (+14)

diff --git a/llvm/lib/IR/Operator.cpp b/llvm/lib/IR/Operator.cpp
index 495769279e3363..7b4449cd825f9b 100644
--- a/llvm/lib/IR/Operator.cpp
+++ b/llvm/lib/IR/Operator.cpp
@@ -28,8 +28,9 @@ bool Operator::hasPoisonGeneratingFlags() const {
     return OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap();
   }
   case Instruction::Trunc: {
-    auto *TI = dyn_cast<TruncInst>(this);
-    return TI->hasNoUnsignedWrap() || TI->hasNoSignedWrap();
+    if (auto *TI = dyn_cast<TruncInst>(this))
+      return TI->hasNoUnsignedWrap() || TI->hasNoSignedWrap();
+    return false;
   }
   case Instruction::UDiv:
   case Instruction::SDiv:
diff --git a/llvm/test/Transforms/FunctionAttrs/noundef.ll b/llvm/test/Transforms/FunctionAttrs/noundef.ll
index 946b562f39553e..9ab37082a30329 100644
--- a/llvm/test/Transforms/FunctionAttrs/noundef.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noundef.ll
@@ -1,6 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
 ; RUN: opt < %s -passes='function-attrs' -S | FileCheck %s
 
+@g_var = external global [0 x i8]
+
 define i32 @test_ret_constant() {
 ; CHECK-LABEL: define noundef i32 @test_ret_constant(
 ; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
@@ -152,3 +154,15 @@ define i32 @test_ret_constant_msan() sanitize_memory {
 ;
   ret i32 0
 }
+
+define i64 @test_trunc_with_constexpr() {
+; CHECK-LABEL: define noundef i64 @test_trunc_with_constexpr(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT:    [[ADD:%.*]] = add i32 trunc (i64 sub (i64 0, i64 ptrtoint (ptr @g_var to i64)) to i32), 1
+; CHECK-NEXT:    [[CONV:%.*]] = sext i32 [[ADD]] to i64
+; CHECK-NEXT:    ret i64 [[CONV]]
+;
+  %add = add i32 trunc (i64 sub (i64 0, i64 ptrtoint (ptr @g_var to i64)) to i32), 1
+  %conv = sext i32 %add to i64
+  ret i64 %conv
+}

[elhewaty]

@dtcxzyw please review

[shiltian]

LG

[shiltian]

This style is really bad. Either use a cast directly w/o a check or check the result before use.

[ronlieb]

i applied your fix to our downstream builds that saw a similar issue ,and it resolved.
thanks will let someone else approve.

[dtcxzyw]

LGTM.

[elhewaty]

@dtcxzyw ping, I think this is ready to be merged, you and @shiltian approved.