[llvm] r331935 - [InstCombine] Widen guards with conditions between

Evgenii Stepanov via llvm-commits llvm-commits at lists.llvm.org
Wed May 9 17:13:29 PDT 2018


Thanks for the quick fix!

On Wed, May 9, 2018 at 5:09 PM, Philip Reames <listmail at philipreames.com>
wrote:

> Fixed.  And thanks for the email btw.
>
> Committed revision 331944.
>
>
> On 05/09/2018 05:00 PM, Philip Reames via llvm-commits wrote:
>
> patch in progress, eta < 5 minutes
>
> On 05/09/2018 04:57 PM, Evgenii Stepanov wrote:
>
> Breaks WERROR,
> http://lab.llvm.org:8011/builders/sanitizer-x86_64-
> linux/builds/11432/steps/bootstrap%20clang/logs/stdio
>
> On Wed, May 9, 2018 at 3:56 PM, Philip Reames via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: reames
>> Date: Wed May  9 15:56:32 2018
>> New Revision: 331935
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=331935&view=rev
>> Log:
>> [InstCombine] Widen guards with conditions between
>>
>> The previous handling for guard widening in InstCombine was extremely
>> restrictive. In particular, it didn't handle the common case where we had
>> two guards separated by a single icmp. Handle this by scanning through a
>> small fixed window of instructions to find the next guard if needed.
>>
>> Differential Revision: https://reviews.llvm.org/D46203
>>
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
>>     llvm/trunk/test/Transforms/InstCombine/call-guard.ll
>>
>> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transform
>> s/InstCombine/InstCombineCalls.cpp?rev=331935&r1=331934&r2=
>> 331935&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
>> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Wed May
>> 9 15:56:32 2018
>> @@ -79,6 +79,13 @@ static cl::opt<unsigned> UnfoldElementAt
>>      cl::desc("Maximum number of elements in atomic memcpy the optimizer
>> is "
>>               "allowed to unfold"));
>>
>> +static cl::opt<unsigned> GuardWideningWindow(
>> +    "instcombine-guard-widening-window",
>> +    cl::init(3),
>> +    cl::desc("How wide an instruction window to bypass looking for "
>> +             "another guard"));
>> +
>> +
>>  /// Return the specified type promoted as it would be to pass though a
>> va_arg
>>  /// area.
>>  static Type *getPromotedType(Type *Ty) {
>> @@ -3624,8 +3631,16 @@ Instruction *InstCombiner::visitCallInst
>>    }
>>
>>    case Intrinsic::experimental_guard: {
>> -    // Is this guard followed by another guard?
>> +    // Is this guard followed by another guard?  We scan forward over a
>> small
>> +    // fixed window of instructions to handle common cases with
>> conditions
>> +    // computed between guards.
>>      Instruction *NextInst = II->getNextNode();
>> +    for (int i = 0; i < GuardWideningWindow; i++) {
>> +      // Note: Using context-free form to avoid compile time blow up
>> +      if (!isSafeToSpeculativelyExecute(NextInst))
>> +        break;
>> +      NextInst = NextInst->getNextNode();
>> +    }
>>      Value *NextCond = nullptr;
>>      if (match(NextInst,
>>                m_Intrinsic<Intrinsic::experi
>> mental_guard>(m_Value(NextCond)))) {
>> @@ -3636,6 +3651,12 @@ Instruction *InstCombiner::visitCallInst
>>          return eraseInstFromFunction(*NextInst);
>>
>>        // Otherwise canonicalize guard(a); guard(b) -> guard(a & b).
>> +      Instruction* MoveI = II->getNextNode();
>> +      while (MoveI != NextInst) {
>> +        auto *Temp = MoveI;
>> +        MoveI = MoveI->getNextNode();
>> +        Temp->moveBefore(II);
>> +      }
>>        II->setArgOperand(0, Builder.CreateAnd(CurrCond, NextCond));
>>        return eraseInstFromFunction(*NextInst);
>>      }
>>
>> Modified: llvm/trunk/test/Transforms/InstCombine/call-guard.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transfor
>> ms/InstCombine/call-guard.ll?rev=331935&r1=331934&r2=331935&view=diff
>> ============================================================
>> ==================
>> --- llvm/trunk/test/Transforms/InstCombine/call-guard.ll (original)
>> +++ llvm/trunk/test/Transforms/InstCombine/call-guard.ll Wed May  9
>> 15:56:32 2018
>> @@ -30,3 +30,81 @@ define void @test_guard_adjacent_diff_co
>>    call void(i1, ...) @llvm.experimental.guard( i1 %C, i32 789 )[
>> "deopt"() ]
>>    ret void
>>  }
>> +
>> +; This version tests for the common form where the conditions are
>> +; between the guards
>> +define void @test_guard_adjacent_diff_cond2(i32 %V1, i32 %V2) {
>> +; CHECK-LABEL: @test_guard_adjacent_diff_cond2(
>> +; CHECK-NEXT:    %1 = and i32 %V1, %V2
>> +; CHECK-NEXT:    %2 = icmp slt i32 %1, 0
>> +; CHECK-NEXT:    %and = and i32 %V1, 255
>> +; CHECK-NEXT:    %C = icmp ult i32 %and, 129
>> +; CHECK-NEXT:    %3 = and i1 %2, %C
>> +; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 %3, i32
>> 123) [ "deopt"() ]
>> +; CHECK-NEXT:    ret void
>> +  %A = icmp slt i32 %V1, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %A, i32 123 )[
>> "deopt"() ]
>> +  %B = icmp slt i32 %V2, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %B, i32 456 )[
>> "deopt"() ]
>> +  %and = and i32 %V1, 255
>> +  %C = icmp sle i32 %and, 128
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %C, i32 789 )[
>> "deopt"() ]
>> +  ret void
>> +}
>> +
>> +; Might not be legal to hoist the load above the first guard since the
>> +; guard might control dereferenceability
>> +define void @negative_load(i32 %V1, i32* %P) {
>> +; CHECK-LABEL: @negative_load
>> +; CHECK:    @llvm.experimental.guard
>> +; CHECK:    @llvm.experimental.guard
>> +  %A = icmp slt i32 %V1, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %A, i32 123 )[
>> "deopt"() ]
>> +  %V2 = load i32, i32* %P
>> +  %B = icmp slt i32 %V2, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %B, i32 456 )[
>> "deopt"() ]
>> +  ret void
>> +}
>> +
>> +define void @deref_load(i32 %V1, i32* dereferenceable(4) %P) {
>> +; CHECK-LABEL: @deref_load
>> +; CHECK-NEXT:  %V2 = load i32, i32* %P, align 4
>> +; CHECK-NEXT:  %1 = and i32 %V2, %V1
>> +; CHECK-NEXT:  %2 = icmp slt i32 %1, 0
>> +; CHECK-NEXT:  call void (i1, ...) @llvm.experimental.guard(i1 %2, i32
>> 123) [ "deopt"() ]
>> +  %A = icmp slt i32 %V1, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %A, i32 123 )[
>> "deopt"() ]
>> +  %V2 = load i32, i32* %P
>> +  %B = icmp slt i32 %V2, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %B, i32 456 )[
>> "deopt"() ]
>> +  ret void
>> +}
>> +
>> +; The divide might fault above the guard
>> +define void @negative_div(i32 %V1, i32 %D) {
>> +; CHECK-LABEL: @negative_div
>> +; CHECK:    @llvm.experimental.guard
>> +; CHECK:    @llvm.experimental.guard
>> +  %A = icmp slt i32 %V1, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %A, i32 123 )[
>> "deopt"() ]
>> +  %V2 = udiv i32 %V1, %D
>> +  %B = icmp slt i32 %V2, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %B, i32 456 )[
>> "deopt"() ]
>> +  ret void
>> +}
>> +
>> +; Highlight the limit of the window in a case which would otherwise be
>> mergable
>> +define void @negative_window(i32 %V1, i32 %a, i32 %b, i32 %c, i32 %d) {
>> +; CHECK-LABEL: @negative_window
>> +; CHECK:    @llvm.experimental.guard
>> +; CHECK:    @llvm.experimental.guard
>> +  %A = icmp slt i32 %V1, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %A, i32 123 )[
>> "deopt"() ]
>> +  %V2 = add i32 %a, %b
>> +  %V3 = add i32 %V2, %c
>> +  %V4 = add i32 %V3, %d
>> +  %B = icmp slt i32 %V4, 0
>> +  call void(i1, ...) @llvm.experimental.guard( i1 %B, i32 456 )[
>> "deopt"() ]
>> +  ret void
>> +}
>> +
>>
>>
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