[ValueTracking] do not try to peek through bitcasts in computeKnownBitsFromAssume()

There are no tests for this case, and I'm not sure how it could ever work,
so I'm just removing this option from the matcher. This should fix PR40940:
https://bugs.llvm.org/show_bug.cgi?id=40940

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355292 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index b4473f8..64250f6 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -617,9 +617,7 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
       continue;
 
     Value *A, *B;
-    auto m_V = m_CombineOr(m_Specific(V),
-                           m_CombineOr(m_PtrToInt(m_Specific(V)),
-                           m_BitCast(m_Specific(V))));
+    auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
 
     CmpInst::Predicate Pred;
     uint64_t C;

diff --git a/test/Transforms/InstCombine/assume.ll b/test/Transforms/InstCombine/assume.ll
index f861741..ec345b2 100644 (file)
--- a/test/Transforms/InstCombine/assume.ll
+++ b/test/Transforms/InstCombine/assume.ll
@@ -320,6 +320,24 @@ define void @debug_interference(i8 %x) {
   ret void
 }
 
+; This would crash.
+; Does it ever make sense to peek through a bitcast of the icmp operand?
+
+define i32 @PR40940(<4 x i8> %x) {
+; CHECK-LABEL: @PR40940(
+; CHECK-NEXT:    [[SHUF:%.*]] = shufflevector <4 x i8> [[X:%.*]], <4 x i8> undef, <4 x i32> <i32 1, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    [[T2:%.*]] = bitcast <4 x i8> [[SHUF]] to i32
+; CHECK-NEXT:    [[T3:%.*]] = icmp ult i32 [[T2]], 65536
+; CHECK-NEXT:    call void @llvm.assume(i1 [[T3]])
+; CHECK-NEXT:    ret i32 [[T2]]
+;
+  %shuf = shufflevector <4 x i8> %x, <4 x i8> undef, <4 x i32> <i32 1, i32 1, i32 2, i32 3>
+  %t2 = bitcast <4 x i8> %shuf to i32
+  %t3 = icmp ult i32 %t2, 65536
+  call void @llvm.assume(i1 %t3)
+  ret i32 %t2
+}
+
 declare void @llvm.dbg.value(metadata, metadata, metadata)
 
 !llvm.dbg.cu = !{!0}