[llvm] r301950 - SpeculativeExecution: Stop using whitelist for costs

Tom Stellard via llvm-commits llvm-commits at lists.llvm.org
Wed May 10 05:59:47 PDT 2017


On 05/10/2017 08:40 AM, Chandler Carruth via llvm-commits wrote:
> FYI, I'm reverting this. See the review thread (https://reviews.llvm.org/D24544) where I've provided details on the fundamental issue.
> 

There was another bug introduced by this commit too:

https://bugs.llvm.org//show_bug.cgi?id=32964

-Tom
> On Tue, May 2, 2017 at 11:15 AM Matt Arsenault via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> 
>     Author: arsenm
>     Date: Tue May  2 13:02:18 2017
>     New Revision: 301950
> 
>     URL: http://llvm.org/viewvc/llvm-project?rev=301950&view=rev
>     Log:
>     SpeculativeExecution: Stop using whitelist for costs
> 
>     Just let TTI's cost do this instead of arbitrarily restricting
>     this.
> 
>     Added:
>         llvm/trunk/test/Transforms/SpeculativeExecution/spec-other.ll
>         llvm/trunk/test/Transforms/SpeculativeExecution/spec-vector.ll
>     Modified:
>         llvm/trunk/lib/Transforms/Scalar/SpeculativeExecution.cpp
> 
>     Modified: llvm/trunk/lib/Transforms/Scalar/SpeculativeExecution.cpp
>     URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SpeculativeExecution.cpp?rev=301950&r1=301949&r2=301950&view=diff
>     ==============================================================================
>     --- llvm/trunk/lib/Transforms/Scalar/SpeculativeExecution.cpp (original)
>     +++ llvm/trunk/lib/Transforms/Scalar/SpeculativeExecution.cpp Tue May  2 13:02:18 2017
>     @@ -208,47 +208,6 @@ bool SpeculativeExecutionPass::runOnBasi
>        return false;
>      }
> 
>     -static unsigned ComputeSpeculationCost(const Instruction *I,
>     -                                       const TargetTransformInfo &TTI) {
>     -  switch (Operator::getOpcode(I)) {
>     -    case Instruction::GetElementPtr:
>     -    case Instruction::Add:
>     -    case Instruction::Mul:
>     -    case Instruction::And:
>     -    case Instruction::Or:
>     -    case Instruction::Select:
>     -    case Instruction::Shl:
>     -    case Instruction::Sub:
>     -    case Instruction::LShr:
>     -    case Instruction::AShr:
>     -    case Instruction::Xor:
>     -    case Instruction::ZExt:
>     -    case Instruction::SExt:
>     -    case Instruction::Call:
>     -    case Instruction::BitCast:
>     -    case Instruction::PtrToInt:
>     -    case Instruction::IntToPtr:
>     -    case Instruction::AddrSpaceCast:
>     -    case Instruction::FPToUI:
>     -    case Instruction::FPToSI:
>     -    case Instruction::UIToFP:
>     -    case Instruction::SIToFP:
>     -    case Instruction::FPExt:
>     -    case Instruction::FPTrunc:
>     -    case Instruction::FAdd:
>     -    case Instruction::FSub:
>     -    case Instruction::FMul:
>     -    case Instruction::FDiv:
>     -    case Instruction::FRem:
>     -    case Instruction::ICmp:
>     -    case Instruction::FCmp:
>     -      return TTI.getUserCost(I);
>     -
>     -    default:
>     -      return UINT_MAX; // Disallow anything not whitelisted.
>     -  }
>     -}
>     -
>      bool SpeculativeExecutionPass::considerHoistingFromTo(
>          BasicBlock &FromBlock, BasicBlock &ToBlock) {
>        SmallSet<const Instruction *, 8> NotHoisted;
>     @@ -264,7 +223,7 @@ bool SpeculativeExecutionPass::considerH
> 
>        unsigned TotalSpeculationCost = 0;
>        for (auto& I : FromBlock) {
>     -    const unsigned Cost = ComputeSpeculationCost(&I, *TTI);
>     +    const unsigned Cost = TTI->getUserCost(&I);
>          if (Cost != UINT_MAX && isSafeToSpeculativelyExecute(&I) &&
>              AllPrecedingUsesFromBlockHoisted(&I)) {
>            TotalSpeculationCost += Cost;
> 
>     Added: llvm/trunk/test/Transforms/SpeculativeExecution/spec-other.ll
>     URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SpeculativeExecution/spec-other.ll?rev=301950&view=auto
>     ==============================================================================
>     --- llvm/trunk/test/Transforms/SpeculativeExecution/spec-other.ll (added)
>     +++ llvm/trunk/test/Transforms/SpeculativeExecution/spec-other.ll Tue May  2 13:02:18 2017
>     @@ -0,0 +1,32 @@
>     +; RUN: opt < %s -S -speculative-execution \
>     +; RUN:   -spec-exec-max-speculation-cost 4 -spec-exec-max-not-hoisted 3 \
>     +; RUN:   | FileCheck %s
>     +
>     +; CHECK-LABEL: @ifThen_extractvalue(
>     +; CHECK: extractvalue
>     +; CHECK: br i1 true
>     +define void @ifThen_extractvalue() {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = extractvalue { i32, i32 } undef, 0
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
>     +; CHECK-LABEL: @ifThen_insertvalue(
>     +; CHECK: insertvalue
>     +; CHECK: br i1 true
>     +define void @ifThen_insertvalue() {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = insertvalue { i32, i32 } undef, i32 undef, 0
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
> 
>     Added: llvm/trunk/test/Transforms/SpeculativeExecution/spec-vector.ll
>     URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SpeculativeExecution/spec-vector.ll?rev=301950&view=auto
>     ==============================================================================
>     --- llvm/trunk/test/Transforms/SpeculativeExecution/spec-vector.ll (added)
>     +++ llvm/trunk/test/Transforms/SpeculativeExecution/spec-vector.ll Tue May  2 13:02:18 2017
>     @@ -0,0 +1,73 @@
>     +; RUN: opt < %s -S -speculative-execution \
>     +; RUN:   -spec-exec-max-speculation-cost 4 -spec-exec-max-not-hoisted 3 \
>     +; RUN:   | FileCheck %s
>     +
>     +; CHECK-LABEL: @ifThen_extractelement_constindex(
>     +; CHECK: extractelement
>     +; CHECK: br i1 true
>     +define void @ifThen_extractelement_constindex() {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = extractelement <4 x i32> undef, i32 0
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
>     +; CHECK-LABEL: @ifThen_extractelement_varindex(
>     +; CHECK: extractelement
>     +; CHECK: br i1 true
>     +define void @ifThen_extractelement_varindex(i32 %idx) {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = extractelement <4 x i32> undef, i32 %idx
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
>     +; CHECK-LABEL: @ifThen_insertelement_constindex(
>     +; CHECK: insertelement
>     +; CHECK: br i1 true
>     +define void @ifThen_insertelement_constindex() {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = insertelement <4 x i32> undef, i32 undef, i32 0
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
>     +; CHECK-LABEL: @ifThen_insertelement_varindex(
>     +; CHECK: insertelement
>     +; CHECK: br i1 true
>     +define void @ifThen_insertelement_varindex(i32 %idx) {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = insertelement <4 x i32> undef, i32 undef, i32 %idx
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
>     +
>     +; CHECK-LABEL: @ifThen_shufflevector(
>     +; CHECK: shufflevector
>     +; CHECK: br i1 true
>     +define void @ifThen_shufflevector() {
>     +  br i1 true, label %a, label %b
>     +
>     +a:
>     +  %x = shufflevector <4 x i32> undef, <4 x i32> undef, <4 x i32> undef
>     +  br label %b
>     +
>     +b:
>     +  ret void
>     +}
> 
> 
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