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Cannot select `fmaximum` for `f128` #65886

Open unterumarmung opened 1 year ago

unterumarmung commented 1 year ago

When working on Simplifying Optimization of Flang intrinsics codegen, it was discovered that it is not possible to use llvm.intr.maximum.f128.

1. Original Fortran program

subroutine test(x, t)
  real(16) :: x(100), t
  t = maxval(x)
end subroutine test
$ ./build/bin/flang-new -c -O2 f.f90
Error log 
LLVM ERROR: Cannot select: t27: f128 = fmaximum contract t26, t25
  t26: f128,ch = load<(load (s128) from %ir.scevgep, !tbaa !3)> t0, t5, undef:i64
    t5: i64 = add t2, t4
      t2: i64,ch = CopyFromReg t0, Register:i64 %4
        t1: i64 = Register %4
      t4: i64,ch = CopyFromReg t0, Register:i64 %0
        t3: i64 = Register %0
    t9: i64 = undef
  t25: f128 = fmaximum contract t24, t21
    t24: f128,ch = load<(load (s128) from %ir.scevgep2, !tbaa !3)> t0, t23, undef:i64
      t23: i64 = add t5, Constant:i64<-16>
        t5: i64 = add t2, t4
          t2: i64,ch = CopyFromReg t0, Register:i64 %4
            t1: i64 = Register %4
          t4: i64,ch = CopyFromReg t0, Register:i64 %0
            t3: i64 = Register %0
        t22: i64 = Constant<-16>
      t9: i64 = undef
    t21: f128 = fmaximum contract t20, t17
      t20: f128,ch = load<(load (s128) from %ir.scevgep4, !tbaa !3)> t0, t19, undef:i64
        t19: i64 = add t5, Constant:i64<-32>
          t5: i64 = add t2, t4
            t2: i64,ch = CopyFromReg t0, Register:i64 %4
              t1: i64 = Register %4
            t4: i64,ch = CopyFromReg t0, Register:i64 %0
              t3: i64 = Register %0
          t18: i64 = Constant<-32>
        t9: i64 = undef
      t17: f128 = fmaximum contract t16, t13
        t16: f128,ch = load<(load (s128) from %ir.scevgep6, !tbaa !3)> t0, t15, undef:i64
          t15: i64 = add t5, Constant:i64<-48>
            t5: i64 = add t2, t4
              t2: i64,ch = CopyFromReg t0, Register:i64 %4
                t1: i64 = Register %4
              t4: i64,ch = CopyFromReg t0, Register:i64 %0
                t3: i64 = Register %0
            t14: i64 = Constant<-48>
          t9: i64 = undef
        t13: f128 = fmaximum contract t10, t12
          t10: f128,ch = load<(load (s128) from %ir.scevgep8, !tbaa !3)> t0, t7, undef:i64
            t7: i64 = add t5, Constant:i64<-64>
              t5: i64 = add t2, t4
                t2: i64,ch = CopyFromReg t0, Register:i64 %4
                  t1: i64 = Register %4
                t4: i64,ch = CopyFromReg t0, Register:i64 %0
                  t3: i64 = Register %0
              t6: i64 = Constant<-64>
            t9: i64 = undef
          t12: f128,ch = CopyFromReg t0, Register:f128 %1
            t11: f128 = Register %1
In function: test_
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/unterumarmung/dev/llvm-project/build/bin/flang-new -fc1 -triple x86_64-unknown-linux-gnu -emit-obj -fcolor-diagnostics -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -O2 -o f.o -x f95-cpp-input f.f90
1.      Running pass 'Function Pass Manager' on module 'FIRModule'.
2.      Running pass 'X86 DAG->DAG Instruction Selection' on function '@test_'
 #0 0x00000000014e45f7 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x14e45f7)
 #1 0x00000000014e205e llvm::sys::RunSignalHandlers() (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x14e205e)
 #2 0x00000000014e4f4f SignalHandler(int) Signals.cpp:0:0
 #3 0x00007fbbb0211420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #4 0x00007fbbafc0e00b raise /build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/raise.c:51:1
 #5 0x00007fbbafbed859 abort /build/glibc-SzIz7B/glibc-2.31/stdlib/abort.c:81:7
 #6 0x0000000001487f43 llvm::report_fatal_error(llvm::Twine const&, bool) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x1487f43)
 #7 0x00000000019ca53e llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19ca53e)
 #8 0x00000000019c978c llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19c978c)
 #9 0x0000000001178537 (anonymous namespace)::X86DAGToDAGISel::Select(llvm::SDNode*) X86ISelDAGToDAG.cpp:0:0
#10 0x00000000019bdfd5 llvm::SelectionDAGISel::DoInstructionSelection() (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19bdfd5)
#11 0x00000000019bceef llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19bceef)
#12 0x00000000019bab01 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19bab01)
#13 0x00000000019b7524 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x19b7524)
#14 0x000000000116a2e9 (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) X86ISelDAGToDAG.cpp:0:0
#15 0x0000000004010d85 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x4010d85)
#16 0x000000000579f404 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x579f404)
#17 0x00000000057a5f01 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x57a5f01)
#18 0x000000000579fab1 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x579fab1)
#19 0x0000000001b0554e Fortran::frontend::CodeGenAction::executeAction() (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x1b0554e)
#20 0x0000000001516f8c Fortran::frontend::FrontendAction::execute() (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x1516f8c)
#21 0x0000000001504976 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x1504976)
#22 0x000000000151b798 Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x151b798)
#23 0x00000000010a2987 fc1_main(llvm::ArrayRef, char const*) (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x10a2987)
#24 0x00000000010a0f92 main (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x10a0f92)
#25 0x00007fbbafbef083 __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:342:3
#26 0x00000000010a0aae _start (/home/unterumarmung/dev/llvm-project/build/bin/flang-new+0x10a0aae)
flang-new: error: unable to execute command: Aborted
flang-new: error: flang frontend command failed due to signal (use -v to see invocation)
flang-new version 18.0.0 (https://github.com/llvm/llvm-project 1a0cbb9c32edf64ab620d31242029b31795fcfd8)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/unterumarmung/dev/llvm-project/build/bin
flang-new: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
flang-new: note: diagnostic msg: /tmp/f-b4496e
flang-new: note: diagnostic msg: /tmp/f-b4496e.sh
flang-new: note: diagnostic msg:

********************

Same with -ffast-math flag

2. LLVM IR

; ModuleID = 'FIRModule'
source_filename = "FIRModule"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: nofree nosync nounwind memory(argmem: readwrite)
define void @test_(ptr nocapture readonly %0, ptr nocapture writeonly %1) local_unnamed_addr #0 {
.lr.ph.i:
  br label %2

2:                                                ; preds = %2, %.lr.ph.i
  %3 = phi fp128 [ 0xLFFFFFFFFFFFFFFFFFFFEFFFFFFFFFFFF, %.lr.ph.i ], [ %28, %2 ]
  %4 = phi i64 [ 0, %.lr.ph.i ], [ %29, %2 ]
  %5 = shl i64 %4, 4
  %6 = getelementptr i8, ptr %0, i64 %5
  %7 = load fp128, ptr %6, align 16, !tbaa !3
  %8 = tail call contract fp128 @llvm.maximum.f128(fp128 %7, fp128 %3)
  %9 = shl i64 %4, 4
  %10 = add i64 %9, 16
  %11 = getelementptr i8, ptr %0, i64 %10
  %12 = load fp128, ptr %11, align 16, !tbaa !3
  %13 = tail call contract fp128 @llvm.maximum.f128(fp128 %12, fp128 %8)
  %14 = shl i64 %4, 4
  %15 = add i64 %14, 32
  %16 = getelementptr i8, ptr %0, i64 %15
  %17 = load fp128, ptr %16, align 16, !tbaa !3
  %18 = tail call contract fp128 @llvm.maximum.f128(fp128 %17, fp128 %13)
  %19 = shl i64 %4, 4
  %20 = add i64 %19, 48
  %21 = getelementptr i8, ptr %0, i64 %20
  %22 = load fp128, ptr %21, align 16, !tbaa !3
  %23 = tail call contract fp128 @llvm.maximum.f128(fp128 %22, fp128 %18)
  %24 = shl i64 %4, 4
  %25 = add i64 %24, 64
  %26 = getelementptr i8, ptr %0, i64 %25
  %27 = load fp128, ptr %26, align 16, !tbaa !3
  %28 = tail call contract fp128 @llvm.maximum.f128(fp128 %27, fp128 %23)
  %29 = add nuw nsw i64 %4, 5
  %exitcond.not.i.4 = icmp eq i64 %29, 100
  br i1 %exitcond.not.i.4, label %_FortranAMaxvalReal16x1_contract_simplified.exit, label %2

_FortranAMaxvalReal16x1_contract_simplified.exit: ; preds = %2
  store fp128 %28, ptr %1, align 16, !tbaa !3
  ret void
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare fp128 @llvm.maximum.f128(fp128, fp128) #1

attributes #0 = { nofree nosync nounwind memory(argmem: readwrite) }
attributes #1 = { mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none) }

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

!0 = !{i32 2, !"Debug Info Version", i32 3}
!1 = !{i32 8, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{!4, !4, i64 0}
!4 = !{!"any data access", !5, i64 0}
!5 = !{!"any access", !6, i64 0}
!6 = !{!"Flang Type TBAA Root"}
$ ./build/bin/llc f.ll

3. Reduced LLVM IR

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

define void @test_(fp128 %0) {
.lr.ph.i:
  %1 = tail call fp128 @llvm.maximum.f128(fp128 %0, fp128 0xL00000000000000000000000000000000)
  store fp128 %1, ptr null, align 16
  ret void
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare fp128 @llvm.maximum.f128(fp128, fp128) #0

attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
llvmbot commented 1 year ago

@llvm/issue-subscribers-backend-x86

unterumarmung commented 1 year ago

It was tested only with X86 backend, but I believe this issue might be occur on other backends also

unterumarmung commented 1 year ago

CC: @vzakhari @dcaballe

llvmbot commented 1 year ago

@llvm/issue-subscribers-bug