[ConstProp] Don't fallthorugh for poison constants on vctp and active_lane_mask.

Given a poison constant as input, the dyn_cast to a ConstantInt would
fail so we would fall through to the generic code that attempts to fold
each element of the input vectors. The inputs to these intrinsics are
not vectors though, leading to a compile time crash. Instead bail out
properly for poison values by returning nullptr. This doesn't try to
define what poison means for these intrinsics.

Fixes #56945

3 files changed, 18 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index f8d05eb688e3..38fb50347c30 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -3120,7 +3120,7 @@ static Constant *ConstantFoldFixedVectorCall(
       }
       return ConstantVector::get(NCs);
     }
-    break;
+    return nullptr;
   }
   case Intrinsic::get_active_lane_mask: {
     auto *Op0 = dyn_cast<ConstantInt>(Operands[0]);
@@ -3139,7 +3139,7 @@ static Constant *ConstantFoldFixedVectorCall(
       }
       return ConstantVector::get(NCs);
     }
-    break;
+    return nullptr;
   }
   default:
     break;
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/ARM/mve-vctp.ll b/llvm/test/Transforms/InstSimplify/ConstProp/ARM/mve-vctp.ll
index 34aea14b594c..979fb2e84ba9 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/ARM/mve-vctp.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/ARM/mve-vctp.ll
@@ -259,7 +259,14 @@ entry:
   ret <2 x i1> %int
 }
 
-
+define <4 x float> @poisonc(<4 x float> %a) {
+entry:
+  %new0 = shl i1 0, 1
+  %last = zext i1 %new0 to i32
+  %var27 = call <4 x i1> @llvm.arm.mve.vctp32(i32 %last)
+  %var33 = select <4 x i1> %var27, <4 x float> %a, <4 x float> zeroinitializer
+  ret <4 x float> %var33
+}
 
 declare <2 x i1> @llvm.arm.mve.vctp64(i32)
 declare <4 x i1> @llvm.arm.mve.vctp32(i32)
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/active-lane-mask.ll b/llvm/test/Transforms/InstSimplify/ConstProp/active-lane-mask.ll
index 726038122289..4a879e837f83 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/active-lane-mask.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/active-lane-mask.ll
@@ -292,8 +292,14 @@ entry:
 }
 
 
-
-
+define <4 x float> @poisonc(<4 x float> %a, i32 %n) {
+entry:
+  %new0 = shl i1 0, 1
+  %last = zext i1 %new0 to i32
+  %var27 = call <4 x i1> @llvm.get.active.lane.mask.v4i1.i32(i32 %last, i32 1024)
+  %var33 = select <4 x i1> %var27, <4 x float> %a, <4 x float> zeroinitializer
+  ret <4 x float> %var33
+}
 
 declare <4 x i1> @llvm.get.active.lane.mask.v4i1.i32(i32, i32)
 declare <8 x i1> @llvm.get.active.lane.mask.v8i1.i32(i32, i32)