[PATCH] D56772: [MIR] Add simple PRE pass to MachineCSE

[Anton Afanasyev via Phabricator via llvm-commits]

anton-afanasyev added a comment.

In D56772#1537772 <https://reviews.llvm.org/D56772#1537772>, @john.brawn wrote:

> This is causing incorrect code generation for this piece of IR:
>
>   target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
>   target triple = "aarch64-arm-none-eabi"
>  
>   @var = hidden local_unnamed_addr global i32 0, align 4
>   @_ZTIi = external dso_local constant i8*
>   declare dso_local void @_Z2fnv() local_unnamed_addr #1
>   declare dso_local i32 @__gxx_personality_v0(...)
>   declare i32 @llvm.eh.typeid.for(i8*) #2
>   declare dso_local i8* @__cxa_begin_catch(i8*) local_unnamed_addr
>   declare dso_local void @__cxa_end_catch() local_unnamed_addr
>  
>   define hidden i32 @_Z7examplev() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
>   entry:
>     invoke void @_Z2fnv()
>             to label %try.cont unwind label %lpad
>  
>   lpad:                                             ; preds = %entry
>     %0 = landingpad { i8*, i32 }
>             catch i8* bitcast (i8** @_ZTIi to i8*)
>             catch i8* null
>     %1 = extractvalue { i8*, i32 } %0, 0
>     %2 = extractvalue { i8*, i32 } %0, 1
>     %3 = tail call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*))
>     %matches = icmp eq i32 %2, %3
>     %4 = tail call i8* @__cxa_begin_catch(i8* %1)
>     %5 = load i32, i32* @var, align 4
>     br i1 %matches, label %catch1, label %catch
>  
>   catch1:                                           ; preds = %lpad
>     %or3 = or i32 %5, 4
>     store i32 %or3, i32* @var, align 4
>     tail call void @__cxa_end_catch()
>     br label %try.cont
>  
>   try.cont:                                         ; preds = %entry, %catch1, %catch
>     %6 = load i32, i32* @var, align 4
>     ret i32 %6
>  
>   catch:                                            ; preds = %lpad
>     %or = or i32 %5, 8
>     store i32 %or, i32* @var, align 4
>     tail call void @__cxa_end_catch()
>     br label %try.cont
>   }
>
>
> As part of the accesses to var an ADRP instruction is being generated and MachineCSE is hoisting it to the entry block, but it gets hoisted to after the call to fn so when we catch an exception the ADRP hasn't been executed so the loads and stores use an undefined base register.


Hi @john.brawn , thanks, I'm looking into it. At first glance, this instruction should have special flag to being non-hoistable.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56772/new/

https://reviews.llvm.org/D56772