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I have created a small ll file to reproduce the problem.

I used the intrinsic function llvm.arm.space to introduce space between the beginning of the code and the jump table.

If the first argument of llvm.arm.space is higher than INT\_MAX (2147483647), then the bug is hit. Lower or equal to that value, it passes. It looks like a precision issue. Does this sound familiar to someone?

; ModuleID = 'test.c'

target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"

target triple = "armv5e-none-linux-androideabi"

declare i32 @llvm.arm.space(i32, i32)

; Function Attrs: nounwind

define i32 @main() #0 {

entry:

%retval = alloca i32, align 4

%a = alloca i32, align 4

store i32 0, i32\* %retval

store i32 0, i32\* %a, align 4

%0 = load i32\* %a, align 4

call i32 @llvm.arm.space(i32 2147483647, i32 undef)

switch i32 %0, label %sw.default \[

i32 0, label %sw.bb

i32 1, label %sw.bb1

i32 2, label %sw.bb2

i32 3, label %sw.bb3

sw.bb: ; preds = %entry

store i32 1, i32\* %retval

br label %return

sw.bb1: ; preds = %entry

store i32 2, i32\* %retval

br label %return

sw.bb2: ; preds = %entry

store i32 3, i32\* %retval

br label %return

sw.bb3: ; preds = %entry

store i32 4, i32\* %retval

br label %return

sw.default: ; preds = %entry

br label %sw.epilog

sw.epilog: ; preds = %sw.default

store i32 0, i32\* %retval

br label %return

return: ; preds = %sw.epilog, %sw.bb3, %sw.bb2, %sw.bb1, %sw.bb

%2 = load i32\* %retval

ret i32 %2

}

; Function Attrs: nounwind

declare i32 @rand() #0

attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="true" }

attributes #1 = { nounwind }

!llvm.module.flags = !{!0, !1, !2}

!llvm.ident = !{!3}

!0 = !{i32 1, !"wchar\_size", i32 4}

!1 = !{i32 1, !"min\_enum\_size", i32 4}

!2 = !{i32 1, !"PIC Level", i32 1}

!3 = !{!"clang version 3.7.0 (trunk 229364)"}

2015-07-06 21:13 GMT+03:00 Eric Bentura <ebentura@gmail.com>:

It is certainly helping - Thanks Renato.

2015-07-06 18:39 GMT+03:00 Renato Golin <renato.golin@linaro.org>:
On 6 July 2015 at 16:32, Eric Bentura <ebentura@gmail.com> wrote:
\> I tried to build the object file using clang 3.7 and it fails with the same
\> error.
\> Where should I look at in the ARM backend to understand what happens?
\> Where the jump table instruction is generated and supposed to be relaxed?

Have a look at lib/Target/ARM/ARMConstantIslandPass.cpp, especially
where Tim's patch touches:

http://llvm.org/viewvc/llvm-project?view=revision&revision=238680

Instruction relaxation rules should be in the TableGen files, I think,
but that means it could be in a number of places.

Step through lib/Target/ARM/ARMAsmPrinter.cpp, at
ARMAsmPrinter::EmitJumpTableInsts and see what the operand is.

You'd expect that it would be already relaxed by that point. If it is,
the bug is in the printer. If not, it could be in the instruction
selection process, either ARMISelLowering or during validation, at
ARMISelDAGToDAG.

Hope that helps.

cheers,
\--renato