Ptrtoint / inttoptr issues?

[Chobbes]

This test program returns 0 in vellvm (which is what I expect), and 144 with clang:

define  i8 @main() {
b0:
    %v0 = alloca i32
    store i32 0, i32* %v0, align 1
    %v1 = ptrtoint i32* %v0 to i64
    %v2 = inttoptr i64 %v1 to <{<3 x i8>, [0 x double], i8}>*
    br label %b1

b1:
    %v3 = load <{<3 x i8>, [0 x double], i8}>, <{<3 x i8>, [0 x double], i8}>* %v2, align 1
    %v4 = extractvalue <{<3 x i8>, [0 x double], i8}> %v3, 2
    ret i8 %v4
}

Not sure what clang is doing. The issue persists even without the size 0 memory of the structure:

define  i8 @main() {
b0:
    %v0 = alloca i32
    store i32 0, i32* %v0, align 1
    %v1 = ptrtoint i32* %v0 to i64
    %v2 = inttoptr i64 %v1 to <{<3 x i8>, i8}>*
    br label %b1

b1:
    %v3 = load <{<3 x i8>, i8}>, <{<3 x i8>, i8}>* %v2, align 1
    %v4 = extractvalue <{<3 x i8>, i8}> %v3, 2
    ret i8 %v4
}

However, the issue disappears when directly allocating a packed structure, instead of using ptoi / itop to cast to a packed structure.

[Chobbes]

I've tried a couple of different combinations of types instead of <3 x i8>, and I don't understand the results:

• i24: Issue persists, 144 is returned.
• [3 x i8]: 0 is returned (expected result).
• <{i8, i8, i8}>: 0 is returned.

Interestingly the assembly language for the i24 and <3 x i8> cases is different, but returns the same bogus value. both seem to copy a 32-bit dword value of 0 to the stack, and then read the fifth byte ([rax + 4]) into al. I believe this should be the fourth byte instead ([rax + 3]). Though the registers end up being different, in the array and packed structure cases (which produce identical assembly) this is the case.

<3 x i8> assembly:

	.text
	.intel_syntax noprefix
	.file	"temporary_vellvm.ll"
	.globl	main                            # -- Begin function main
	.p2align	4, 0x90
	.type	main,@function
main:                                   # @main
	.cfi_startproc
# %bb.0:                                # %b0
	mov	dword ptr [rsp - 4], 0
	lea	rax, [rsp - 4]
	mov	qword ptr [rsp - 32], rax       # 8-byte Spill
# %bb.1:                                # %b1
	mov	rax, qword ptr [rsp - 32]       # 8-byte Reload
	movzx	ecx, word ptr [rax]
	movd	xmm0, ecx
	movaps	xmmword ptr [rsp - 24], xmm0
	mov	cl, byte ptr [rax + 2]
	mov	al, byte ptr [rax + 4]
	mov	cl, byte ptr [rsp - 24]
	mov	cl, byte ptr [rsp - 23]
	ret
.Lfunc_end0:
	.size	main, .Lfunc_end0-main
	.cfi_endproc
                                        # -- End function
	.section	".note.GNU-stack","",@progbits
	.addrsig

i24 assembly:

	.text
	.intel_syntax noprefix
	.file	"temporary_vellvm.ll"
	.globl	main                            # -- Begin function main
	.p2align	4, 0x90
	.type	main,@function
main:                                   # @main
	.cfi_startproc
# %bb.0:                                # %b0
	mov	dword ptr [rsp - 4], 0
	lea	rax, [rsp - 4]
	mov	qword ptr [rsp - 16], rax       # 8-byte Spill
# %bb.1:                                # %b1
	mov	rax, qword ptr [rsp - 16]       # 8-byte Reload
	movzx	ecx, word ptr [rax]
	movzx	edx, byte ptr [rax + 2]
	shl	edx, 16
	or	ecx, edx
	mov	al, byte ptr [rax + 4]
	ret
.Lfunc_end0:
	.size	main, .Lfunc_end0-main
	.cfi_endproc
                                        # -- End function
	.section	".note.GNU-stack","",@progbits
	.addrsig

<{i8, i8, i8}> / [3 x i8] assembly:

	.text
	.intel_syntax noprefix
	.file	"temporary_vellvm.ll"
	.globl	main                            # -- Begin function main
	.p2align	4, 0x90
	.type	main,@function
main:                                   # @main
	.cfi_startproc
# %bb.0:                                # %b0
	mov	dword ptr [rsp - 4], 0
	lea	rax, [rsp - 4]
	mov	qword ptr [rsp - 16], rax       # 8-byte Spill
# %bb.1:                                # %b1
	mov	rcx, qword ptr [rsp - 16]       # 8-byte Reload
	mov	al, byte ptr [rcx + 3]
	mov	dl, byte ptr [rcx + 2]
	mov	dl, byte ptr [rcx]
	mov	cl, byte ptr [rcx + 1]
	ret
.Lfunc_end0:
	.size	main, .Lfunc_end0-main
	.cfi_endproc
                                        # -- End function
	.section	".note.GNU-stack","",@progbits
	.addrsig

Is this a bug in LLVM with how i24 and vector members of packed structs are handled with extractvalue? Are the pointer / integer casts illegal?