http://llvm.org/bugs/show_bug.cgi?id=17764
Bug ID: 17764
Summary: llc generates wrong asm at AVX2 from instructions
trunc + select
Product: tools
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: llc
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Reproducer for this issue:
; ModuleID = 'a.s'
target datalayout =
"e-p:64:64:64-S128-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f16:16:16-f32:32:32-f64:64:64-f128:128:128-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: nounwind
define <16 x i16> @foo() {
allocas:
%mask_1 = alloca <16 x i32>
%second = alloca <16 x i16>
%first = alloca <16 x i16>
store <16 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32
-1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1>, <16 x
i32>* %mask_1
store <16 x i16> <i16 2, i16 2, i16 2, i16 2, i16 2, i16 2, i16 2, i16 2, i16
2, i16 2, i16 2, i16 2, i16 2, i16 2, i16 2, i16 2>, <16 x i16>* %first
store <16 x i16> <i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16
7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7, i16 7>, <16 x i16>* %second
%first_load = load <16 x i16>* %first
%second_load = load <16 x i16>* %second
%mask_2 = load <16 x i32>* %mask_1
%mask_3 = trunc <16 x i32> %mask_2 to <16 x i1>
%result = select <16 x i1> %mask_3, <16 x i16> %first_load, <16 x i16>
%second_load
ret <16 x i16> %result
}
At AVX2 llc generates asm code which ends in instuction:
vpblendvb %ymm2, %ymm0, %ymm1, %ymm0
where ymm2 = 16 x -1, ymm0 = 16 x 7, and ymm1 = 16 x 2.
This instruction makes ymm0 = 16 x 7 and it is wrong because LLVM instrunction
select <16 x i1> %mask_3, <16 x i16> %first_load, <16 x i16> %second_load
should return first_load which is 16 x 2.
So function returns 16 x 7 instead of 16 x 2
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