performance problem with indirection

[regehr]

here's an example where the asm memory model isn't yet making verification fast; this one exits with SMT Error: unclassified exception after about 2.5 minutes

source_filename = "M2"
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-linux-gnu"

define dso_local i32 @two_stars(ptr noundef %0) #0 {
  %2 = alloca ptr, align 8
  store ptr %0, ptr %2, align 8
  %3 = load ptr, ptr %2, align 8
  %4 = load ptr, ptr %3, align 8
  %5 = load i32, ptr %4, align 4
  ret i32 %5
}

attributes #0 = { noinline nounwind optnone uwtable "frame-pointer"="non-leaf" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+fp-armv8,+neon,+outline-atomics,+v8a,-fmv" }

; ModuleID = 'M2'
source_filename = "M2"
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-linux-gnu"

define i32 @two_stars(ptr %0) local_unnamed_addr {
arm_tv_entry:
  %stack = tail call dereferenceable(640) ptr @myalloc(i32 640)
  %1 = getelementptr inbounds i8, ptr %stack, i64 512
  %2 = ptrtoint ptr %1 to i64
  %3 = ptrtoint ptr %0 to i64
  %a2_1 = add i64 %2, -16
  %4 = inttoptr i64 %a2_1 to ptr
  %5 = getelementptr i8, ptr %4, i64 8
  store i64 %3, ptr %5, align 1
  %a5_1 = load i64, ptr %0, align 1
  %6 = inttoptr i64 %a5_1 to ptr
  %a6_1 = load i32, ptr %6, align 1
  ret i32 %a6_1
}

; Function Attrs: allockind("alloc") allocsize(0)
declare nonnull ptr @myalloc(i32) local_unnamed_addr #0

attributes #0 = { allockind("alloc") allocsize(0) }

regehr@john-home:~/alive2-regehr/tests/arm-tv/pointers$ time ~/alive2-regehr/build/alive-tv double-indirect-1a.ll ~/tgt.ll --tgt-is-asm --smt-to=600000

----------------------------------------
define i32 @two_stars(ptr noundef %#0) {
#1:
  %#2 = alloca i64 8, align 8
  store ptr noundef %#0, ptr %#2, align 8
  %#3 = load ptr, ptr %#2, align 8
  %#4 = load ptr, ptr %#3, align 8
  %#5 = load i32, ptr %#4, align 4
  ret i32 %#5
}
=>
declare ptr @myalloc(i32)

define i32 @two_stars(ptr %#0) asm {
arm_tv_entry:
  %stack = call ptr @myalloc(i32 640) dereferenceable(640) nonnull allockind(alloc) allocsize(0)
  %#1 = gep inbounds ptr %stack, 1 x i64 512
  %#2 = ptrtoint ptr %#1 to i64
  %#3 = ptrtoint ptr %#0 to i64
  %a2_1 = add i64 %#2, -16
  %#4 = int2ptr i64 %a2_1 to ptr
  %#5 = gep ptr %#4, 1 x i64 8
  store i64 %#3, ptr %#5, align 1
  %a5_1 = load i64, ptr %#0, align 1
  %#6 = int2ptr i64 %a5_1 to ptr
  %a6_1 = load i32, ptr %#6, align 1
  ret i32 %a6_1
}
ERROR: SMT Error: unclassified exception

Summary:
  0 correct transformations
  0 incorrect transformations
  1 failed-to-prove transformations
  0 Alive2 errors

real    2m19.009s
user    2m17.265s
sys 0m1.700s
regehr@john-home:~/alive2-regehr/tests/arm-tv/pointers$