[llvm-dev] Optimization issues (Alias Analysis?)

[Peet Nick via llvm-dev]

Hey,

I am currently working on a VM which is based on LLVM and I would like to
use its optimizer, but it somehow it can't detect something very simple (I
guess.)

This is the LLVM IR:

target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
target triple = "i386-unknown-linux-gnu"

%struct.regs = type { i32, i32, i32 }

define void @Test(%struct.regs* noalias nocapture sret, i32, i32, i32)
local_unnamed_addr #0 {
  %5 = add i32 %3, -4
  %6 = inttoptr i32 %5 to i32*
  store i32 %2, i32* %6, align 4

  %7 = add i32 %3, -8
  %8 = inttoptr i32 %7 to i32*
  store i32 %1, i32* %8, align 4

  %9 = load i32, i32* %6, align 4

  %.sroa.0.0..sroa_idx = getelementptr inbounds %struct.regs, %struct.regs*
%0, i32 0, i32 0
  store i32 %9, i32* %.sroa.0.0..sroa_idx, align 4

  %.sroa.4.0..sroa_idx4 = getelementptr inbounds %struct.regs,
%struct.regs* %0, i32 0, i32 1
  store i32 %1, i32* %.sroa.4.0..sroa_idx4, align 4

  %.sroa.7.0..sroa_idx5 = getelementptr inbounds %struct.regs,
%struct.regs* %0, i32 0, i32 2
  store i32 %3, i32* %.sroa.7.0..sroa_idx5, align 4

  ret void
}

This is compiled from some cpp just to reproduce the issue.
The issue here is that the load isn't eliminated and that the third store
isn't directly using %2.

I thought that this might be an issue with the current BasicAliasAnalysis
so I also tried CFL which isn't working either.

~ Nick
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160704/f8fe973b/attachment.html>