[Verifier] Remove invalid verifier check

[skatkov]

Summary

According to LangRef for unordered atomic memory transfer intrinsics
"The first three arguments are the same as they are in the @llvm.memcpy intrinsic, with the added constraint that len is required to be a positive integer multiple of the element_size. If len is not a positive integer multiple of element_size, then the behaviour of the intrinsic is undefined."

So the len is not multiple of element size is just an undefined behavior and verifier should not complain about that
as undefined behavior is allowed in LLVM IR.

This change removes the verifier check for this condition

[reames]

LGTM

Also, you should add an instcombine which converts a UB length into an unreachable idiom. That would help simplify your example you shared privately. (Context: Switch case leading to dead code contains this construct.)

llvm/test/Verifier/element-wise-atomic-memory-intrinsics.ll

11–12

Please remove the check line, being overly specific to a message which no longer exists doesn't add any value.

37–38

Same

63–64

Same

llvm/lib/IR/Verifier.cpp

case Intrinsic::memset_element_unordered_atomic: {
     ConstantInt *ElementSizeCI =
         cast<ConstantInt>(AMI->getRawElementSizeInBytes());
     const APInt &ElementSizeVal = ElementSizeCI->getValue();
     Assert(ElementSizeVal.isPowerOf2(),
            "element size of the element-wise atomic memory intrinsic "
            "must be a power of 2",
            Call);
 
-    if (auto *LengthCI = dyn_cast<ConstantInt>(AMI->getLength())) {
-      uint64_t Length = LengthCI->getZExtValue();
-      uint64_t ElementSize = AMI->getElementSizeInBytes();
-      Assert((Length % ElementSize) == 0,
-             "constant length must be a multiple of the element size in the "
-             "element-wise atomic memory intrinsic",
-             Call);
-    }
-
     auto IsValidAlignment = [&](uint64_t Alignment) {
       return isPowerOf2_64(Alignment) && ElementSizeVal.ule(Alignment);
     };
     uint64_t DstAlignment = AMI->getDestAlignment();
     Assert(IsValidAlignment(DstAlignment),
            "incorrect alignment of the destination argument", Call);
     if (const auto *AMT = dyn_cast<AtomicMemTransferInst>(AMI)) {
       uint64_t SrcAlignment = AMT->getSourceAlignment();

llvm/test/Verifier/element-wise-atomic-memory-intrinsics.ll

 ; RUN: not opt -verify < %s 2>&1 | FileCheck %s
 
 define void @test_memcpy(i8* %P, i8* %Q, i32 %A, i32 %E) {
   ; CHECK: immarg operand has non-immediate parameter
   ; CHECK: i32 %E
   ; CHECK-NEXT: call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 %E)
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 %E)
 
   ; CHECK: element size of the element-wise atomic memory intrinsic must be a power of 2
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 3)
 
-  ; CHECK: constant length must be a multiple of the element size in the element-wise atomic memory intrinsic
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 7, i32 4)
 
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* %P, i8* align 4 %Q, i32 1, i32 1)
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 1 %P, i8* align 4 %Q, i32 4, i32 4)
 
   ; CHECK: incorrect alignment of the source argument
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* %Q, i32 1, i32 1)
   ; CHECK: incorrect alignment of the source argument
   call void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 1 %Q, i32 4, i32 4)
 
   ret void
 }
 
 declare void @llvm.memcpy.element.unordered.atomic.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
 
 define void @test_memmove(i8* %P, i8* %Q, i32 %A, i32 %E) {
   ; CHECK: immarg operand has non-immediate parameter
   ; CHECK-NEXT: i32 %E
   ; CHECK-NEXT: call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 %E)
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 %E)
 
   ; CHECK: element size of the element-wise atomic memory intrinsic must be a power of 2
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 1, i32 3)
 
-  ; CHECK: constant length must be a multiple of the element size in the element-wise atomic memory intrinsic
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 4 %Q, i32 7, i32 4)
 
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* %P, i8* align 4 %Q, i32 1, i32 1)
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 1 %P, i8* align 4 %Q, i32 4, i32 4)
 
   ; CHECK: incorrect alignment of the source argument
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* %Q, i32 1, i32 1)
   ; CHECK: incorrect alignment of the source argument
   call void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* align 4 %P, i8* align 1 %Q, i32 4, i32 4)
 
   ret void
 }
 
 declare void @llvm.memmove.element.unordered.atomic.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
 
 define void @test_memset(i8* %P, i8 %V, i32 %A, i32 %E) {
   ; CHECK: immarg operand has non-immediate parameter
   ; CHECK: i32 %E
   ; CHECK: call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* align 4 %P, i8 %V, i32 1, i32 %E)
   call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* align 4 %P, i8 %V, i32 1, i32 %E)
 
   ; CHECK: element size of the element-wise atomic memory intrinsic must be a power of 2
   call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* align 4 %P, i8 %V, i32 1, i32 3)
 
-  ; CHECK: constant length must be a multiple of the element size in the element-wise atomic memory intrinsic
   call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* align 4 %P, i8 %V, i32 7, i32 4)
 
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* %P, i8 %V, i32 1, i32 1)
   ; CHECK: incorrect alignment of the destination argument
   call void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* align 1 %P, i8 %V, i32 4, i32 4)
 
   ret void
 }
 declare void @llvm.memset.element.unordered.atomic.p0i8.i32(i8* nocapture, i8, i32, i32) nounwind
 
 ; CHECK: input module is broken!