[llvm] r256028 - Enhance BranchProbabilityInfo::calcUnreachableHeuristics for InvokeInst

[Rafael Espíndola via llvm-commits]

Sorry, reverted in 256032 since it broke some tests.

Cheers,
Rafael


On 18 December 2015 at 15:53, Jun Bum Lim via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: junbuml
> Date: Fri Dec 18 14:53:47 2015
> New Revision: 256028
>
> URL: http://llvm.org/viewvc/llvm-project?rev=256028&view=rev
> Log:
> Enhance BranchProbabilityInfo::calcUnreachableHeuristics for InvokeInst
>
> When identifying blocks post-dominated by an unreachable-terminated block
> in BranchProbabilityInfo, consider only the edge to the normal destination
> block if the terminator is InvokeInst and let calcInvokeHeuristics() decide
> edge weights for the InvokeInst.
>
> Modified:
>     llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp
>     llvm/trunk/test/Analysis/BranchProbabilityInfo/noreturn.ll
>     llvm/trunk/test/CodeGen/X86/catchret-empty-fallthrough.ll
>
> Modified: llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp?rev=256028&r1=256027&r2=256028&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp (original)
> +++ llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp Fri Dec 18 14:53:47 2015
> @@ -147,6 +147,16 @@ bool BranchProbabilityInfo::calcUnreacha
>    if (TI->getNumSuccessors() == 1 || UnreachableEdges.empty())
>      return false;
>
> +  // If the terminator is an InvokeInst, check only the normal destination block
> +  // as the unwind edge of InvokeInst is also very unlikely taken.
> +  if (auto *II = dyn_cast<InvokeInst>(TI))
> +    if (PostDominatedByUnreachable.count(II->getNormalDest())) {
> +      PostDominatedByUnreachable.insert(BB);
> +      // Return false here so that edge weights for InvokeInst could be decided
> +      // in calcInvokeHeuristics().
> +      return false;
> +    }
> +
>    uint32_t UnreachableWeight =
>      std::max(UR_TAKEN_WEIGHT / (unsigned)UnreachableEdges.size(), MIN_WEIGHT);
>    for (SmallVectorImpl<unsigned>::iterator I = UnreachableEdges.begin(),
>
> Modified: llvm/trunk/test/Analysis/BranchProbabilityInfo/noreturn.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BranchProbabilityInfo/noreturn.ll?rev=256028&r1=256027&r2=256028&view=diff
> ==============================================================================
> --- llvm/trunk/test/Analysis/BranchProbabilityInfo/noreturn.ll (original)
> +++ llvm/trunk/test/Analysis/BranchProbabilityInfo/noreturn.ll Fri Dec 18 14:53:47 2015
> @@ -77,3 +77,48 @@ abort:
>  exit:
>    ret i32 %b
>  }
> +
> + at _ZTIi = external global i8*
> +
> +; CHECK-LABEL: throwSmallException
> +; CHECK-NOT: invoke i32 @smallFunction
> +define i32 @throwSmallException(i32 %idx, i32 %limit) #0 personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
> +entry:
> +  %cmp = icmp sge i32 %idx, %limit
> +  br i1 %cmp, label %if.then, label %if.end
> +; CHECK: edge entry -> if.then probability is 0x00000800 / 0x80000000 = 0.00%
> +; CHECK: edge entry -> if.end probability is 0x7ffff800 / 0x80000000 = 100.00% [HOT edge]
> +
> +if.then:                                          ; preds = %entry
> +  %exception = call i8* @__cxa_allocate_exception(i64 1) #0
> +  invoke i32 @smallFunction(i32 %idx)
> +          to label %invoke.cont unwind label %lpad
> +; CHECK: edge if.then -> invoke.cont probability is 0x7ffff800 / 0x80000000 = 100.00% [HOT edge]
> +; CHECK: edge if.then -> lpad probability is 0x00000800 / 0x80000000 = 0.00%
> +
> +invoke.cont:                                      ; preds = %if.then
> +  call void @__cxa_throw(i8* %exception, i8* bitcast (i8** @_ZTIi  to i8*), i8* null) #1
> +  unreachable
> +
> +lpad:                                             ; preds = %if.then
> +  %ll = landingpad { i8*, i32 }
> +          cleanup
> +  ret i32 %idx
> +
> +if.end:                                           ; preds = %entry
> +  ret i32 %idx
> +}
> +
> + at a = global i32 4
> +define i32 @smallFunction(i32 %a) {
> +entry:
> +  %r = load volatile i32, i32* @a
> +  ret i32 %r
> +}
> +
> +attributes #0 = { nounwind }
> +attributes #1 = { noreturn }
> +
> +declare i8* @__cxa_allocate_exception(i64)
> +declare i32 @__gxx_personality_v0(...)
> +declare void @__cxa_throw(i8*, i8*, i8*)
>
> Modified: llvm/trunk/test/CodeGen/X86/catchret-empty-fallthrough.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/catchret-empty-fallthrough.ll?rev=256028&r1=256027&r2=256028&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/catchret-empty-fallthrough.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/catchret-empty-fallthrough.ll Fri Dec 18 14:53:47 2015
> @@ -34,12 +34,14 @@ return:
>
>  ; CHECK-LABEL: foo: # @foo
>  ; CHECK: testb $1, %cl
> -; CHECK: jne .LBB0_[[return:[0-9]+]]
> +; CHECK: je .LBB0_[[try:[0-9]+]]
> +; CHECK: .LBB0_[[return:[0-9]+]]:
> +; CHECK: retq
> +; CHECK: .LBB0_[[try]]:
>  ; CHECK: .Ltmp0:
>  ; CHECK: callq bar
>  ; CHECK: .Ltmp1:
>  ; CHECK: .LBB0_[[catch:[0-9]+]]:
> -; CHECK: .LBB0_[[return]]:
>
>  ; CHECK: .seh_handlerdata
>  ; CHECK-NEXT: .Lfoo$parent_frame_offset = 32
>
>
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