[LLVMbugs] [Bug 18014] New: llc handles "sext" instruction with constants incorrect

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18014

            Bug ID: 18014
           Summary: llc handles "sext" instruction with constants
                    incorrect
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: llc
          Assignee: unassignedbugs at nondot.org
          Reporter: ili.filippov at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11580
  --> http://llvm.org/bugs/attachment.cgi?id=11580&action=edit
Reproducer

Reproducer for this issue:

; ModuleID = 'bad.bc'
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 i32 @f_fu(<8 x i32>* %RET, <8 x i32>* %temp) #2 {
allocas:
  %temp_1 = load <8 x i32>* %temp

  %sext_val = sext <8 x i1> <i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1> to
<8 x i32>
  %mask = and <8 x i32> %sext_val, %temp_1

  %one_of_mask = extractelement <8 x i32> %mask, i32 3

  %new_mask = insertelement <8 x i32> zeroinitializer, i32 %one_of_mask, i32 1
  %blend = select <8 x i1> <i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1>, <8
x i32> %new_mask, <8 x i32> zeroinitializer
  store <8 x i32> %blend, <8 x i32>* %RET

  ret i32 %one_of_mask
}

attributes #2 = { nounwind "target-cpu"="corei7-avx"
"target-features"="+sse,+sse2,+sse3,-sse4a,+ssse3,-popcnt,+cmov,+sse4.1,-sse4.2"
}


to reproduce:
llc bad.ll -mcpu=westmere
clang++ -O2 -m64 test.cpp bad.s -o test.run
./test.run

(File test.cpp is attached)

Here we sext i1 array of ones to i32 array of ones. Then and them with input
array and return third element of the result.
We should have an answer 4 (because it is the value of third element of input
array). But we will have answer 0 and it is incorrect. Possible it happens due
to missing pslld and psrad instructions before "and" instruction in generated
asm.

If we comment last strings:
;  %new_mask = insertelement <8 x i32> zeroinitializer, i32 %one_of_mask, i32 1
;  %blend = select <8 x i1> <i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1, i1 1>,
<8 x i32> %new_mask, <8 x i32> zeroinitializer
;  store <8 x i32> %blend, <8 x i32>* %RET

We will have right answer and right shifts in generated asm.

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