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[flang] Add -f[no-]unroll-loops flag #122906

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Merged
DavidTruby merged 5 commits into from
Jan 16, 2025
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[flang] Add -f[no-]unroll-loops flag #122906

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c9b2e58
[flang] Add -f[no-]unroll-loops flag
DavidTruby Jan 8, 2025
d66a7c6
Fix bad rebase and add compiler->frontend forwarding test
DavidTruby Jan 14, 2025
ac03aad
Fix test on x86
DavidTruby Jan 14, 2025
f27462b
Add integration test
DavidTruby Jan 14, 2025
0141e0d
Switch to i64 to simplify tests
DavidTruby Jan 14, 2025
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4 changes: 2 additions & 2 deletions clang/include/clang/Driver/Options.td
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Expand Up @@ -4157,9 +4157,9 @@ def ftrap_function_EQ : Joined<["-"], "ftrap-function=">, Group<f_Group>,
HelpText<"Issue call to specified function rather than a trap instruction">,
MarshallingInfoString<CodeGenOpts<"TrapFuncName">>;
def funroll_loops : Flag<["-"], "funroll-loops">, Group<f_Group>,
HelpText<"Turn on loop unroller">, Visibility<[ClangOption, CC1Option]>;
HelpText<"Turn on loop unroller">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>;
def fno_unroll_loops : Flag<["-"], "fno-unroll-loops">, Group<f_Group>,
HelpText<"Turn off loop unroller">, Visibility<[ClangOption, CC1Option]>;
HelpText<"Turn off loop unroller">, Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>;
def ffinite_loops: Flag<["-"], "ffinite-loops">, Group<f_Group>,
HelpText<"Assume all non-trivial loops are finite.">, Visibility<[ClangOption, CC1Option]>;
def fno_finite_loops: Flag<["-"], "fno-finite-loops">, Group<f_Group>,
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3 changes: 2 additions & 1 deletion clang/lib/Driver/ToolChains/Flang.cpp
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Expand Up @@ -155,7 +155,8 @@ void Flang::addCodegenOptions(const ArgList &Args,
options::OPT_flang_deprecated_no_hlfir,
options::OPT_fno_ppc_native_vec_elem_order,
options::OPT_fppc_native_vec_elem_order,
options::OPT_ftime_report, options::OPT_ftime_report_EQ});
options::OPT_ftime_report, options::OPT_ftime_report_EQ,
options::OPT_funroll_loops, options::OPT_fno_unroll_loops});
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@kiranchandramohan kiranchandramohan Jan 14, 2025

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We can add a forwarding test from the driver to the frontend driver.

}

void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
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1 change: 1 addition & 0 deletions flang/include/flang/Frontend/CodeGenOptions.def
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Expand Up @@ -32,6 +32,7 @@ CODEGENOPT(PrepareForThinLTO , 1, 0) ///< Set when -flto=thin is enabled on the
///< compile step.
CODEGENOPT(StackArrays, 1, 0) ///< -fstack-arrays (enable the stack-arrays pass)
CODEGENOPT(LoopVersioning, 1, 0) ///< Enable loop versioning.
CODEGENOPT(UnrollLoops, 1, 0) ///< Enable loop unrolling
CODEGENOPT(AliasAnalysis, 1, 0) ///< Enable alias analysis pass

CODEGENOPT(Underscoring, 1, 1)
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4 changes: 4 additions & 0 deletions flang/lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -246,6 +246,10 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
clang::driver::options::OPT_fno_loop_versioning, false))
opts.LoopVersioning = 1;

opts.UnrollLoops = args.hasFlag(clang::driver::options::OPT_funroll_loops,
clang::driver::options::OPT_fno_unroll_loops,
(opts.OptimizationLevel > 1));

opts.AliasAnalysis = opts.OptimizationLevel > 0;

// -mframe-pointer=none/non-leaf/all option.
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2 changes: 2 additions & 0 deletions flang/lib/Frontend/FrontendActions.cpp
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Expand Up @@ -1028,6 +1028,8 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
si.registerCallbacks(pic, &mam);
if (ci.isTimingEnabled())
si.getTimePasses().setOutStream(ci.getTimingStreamLLVM());
pto.LoopUnrolling = opts.UnrollLoops;
pto.LoopInterleaving = opts.UnrollLoops;
llvm::PassBuilder pb(targetMachine, pto, pgoOpt, &pic);

// Attempt to load pass plugins and register their callbacks with PB.
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5 changes: 5 additions & 0 deletions flang/test/Driver/funroll-loops.f90
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@@ -0,0 +1,5 @@
! RUN: %flang -### -funroll-loops %s 2>&1 | FileCheck %s -check-prefix UNROLL
! RUN: %flang -### -fno-unroll-loops %s 2>&1 | FileCheck %s -check-prefix NO-UNROLL

! UNROLL: "-funroll-loops"
! NO-UNROLL: "-fno-unroll-loops"
43 changes: 43 additions & 0 deletions flang/test/HLFIR/unroll-loops.fir
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@@ -0,0 +1,43 @@
// RUN: %flang_fc1 -emit-llvm -O1 -funroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
// RUN: %flang_fc1 -emit-llvm -O2 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
// RUN: %flang_fc1 -emit-llvm -O1 -fno-unroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL
// RUN: %flang_fc1 -emit-llvm -O1 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL

// CHECK-LABEL: @unroll
// CHECK-SAME: (ptr nocapture writeonly %[[ARG0:.*]])
func.func @unroll(%arg0: !fir.ref<!fir.array<1000xf64>> {fir.bindc_name = "a"}) {
%scope = fir.dummy_scope : !fir.dscope
%c1000 = arith.constant 1000 : index
%shape = fir.shape %c1000 : (index) -> !fir.shape<1>
%a:2 = hlfir.declare %arg0(%shape) dummy_scope %scope {uniq_name = "unrollEa"} : (!fir.ref<!fir.array<1000xf64>>, !fir.shape<1>, !fir.dscope) -> (!fir.ref<!fir.array<1000xf64>>, !fir.ref<!fir.array<1000xf64>>)
%c1 = arith.constant 1 : index
fir.do_loop %arg1 = %c1 to %c1000 step %c1 {
// CHECK: br label %[[BLK:.*]]
// CHECK: [[BLK]]:
// CHECK-NEXT: %[[IND:.*]] = phi i64 [ 0, %{{.*}} ], [ %[[NIV:.*]], %[[BLK]] ]
// CHECK-NEXT: %[[VIND:.*]] = phi <2 x i64> [ <i64 1, i64 2>, %{{.*}} ], [ %[[NVIND:.*]], %[[BLK]] ]

// NO-UNROLL-NEXT: %[[IV_D:.*]] = uitofp nneg <2 x i64> %[[VIND]] to <2 x double>
// NO-UNROLL-NEXT: %[[GEP:.*]] = getelementptr double, ptr %[[ARG0]], i64 %[[IND]]
// NO-UNROLL-NEXT: store <2 x double> %[[IV_D]], ptr %[[GEP]]
// NO-UNROLL-NEXT: %[[NIV:.*]] = add nuw i64 %{{.*}}, 2
// NO-UNROLL-NEXT: %[[NVIND]] = add <2 x i64> %[[VIND]], splat (i64 2)

// UNROLL-NEXT: %[[VIND1:.*]] = add <2 x i64> %[[VIND]], splat (i64 2)
// UNROLL-NEXT: %[[IV0_D:.*]] = uitofp nneg <2 x i64> %[[VIND]] to <2 x double>
// UNROLL-NEXT: %[[IV1_D:.*]] = uitofp nneg <2 x i64> %[[VIND1]] to <2 x double>
// UNROLL-NEXT: %[[GEP0:.*]] = getelementptr double, ptr %[[ARG0]], i64 %[[IND]]
// UNROLL-NEXT: %[[GEP1:.*]] = getelementptr i8, ptr %[[GEP0]], i64 16
// UNROLL-NEXT: store <2 x double> %[[IV0_D]], ptr %[[GEP0]]
// UNROLL-NEXT: store <2 x double> %[[IV1_D]], ptr %[[GEP1]]
// UNROLL-NEXT: %[[NIV:.*]] = add nuw i64 %[[IND]], 4
// UNROLL-NEXT: %[[NVIND:.*]] = add <2 x i64> %[[VIND]], splat (i64 4)

// CHECK-NEXT: %[[EXIT:.*]] = icmp eq i64 %[[NIV]], 1000
// CHECK-NEXT: br i1 %[[EXIT]], label %{{.*}}, label %[[BLK]]
%iv = fir.convert %arg1 : (index) -> f64
%ai = hlfir.designate %a#0 (%arg1) : (!fir.ref<!fir.array<1000xf64>>, index) -> !fir.ref<f64>
hlfir.assign %iv to %ai : f64, !fir.ref<f64>
}
return
}
37 changes: 37 additions & 0 deletions flang/test/Integration/unroll-loops.f90
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@@ -0,0 +1,37 @@
! RUN: %flang_fc1 -emit-llvm -O1 -funroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
! RUN: %flang_fc1 -emit-llvm -O2 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
! RUN: %flang_fc1 -emit-llvm -O1 -fno-unroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL
! RUN: %flang_fc1 -emit-llvm -O1 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL

! CHECK-LABEL: @unroll
! CHECK-SAME: (ptr nocapture writeonly %[[ARG0:.*]])
subroutine unroll(a)
real(kind=8), intent(out) :: a(1000)
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@kiranchandramohan kiranchandramohan Jan 14, 2025

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Can this be an integer array to avoid the uitofp ?

integer(kind=8) :: i
! CHECK: br label %[[BLK:.*]]
! CHECK: [[BLK]]:
! CHECK-NEXT: %[[IND:.*]] = phi i64 [ 0, %{{.*}} ], [ %[[NIV:.*]], %[[BLK]] ]
! CHECK-NEXT: %[[VIND:.*]] = phi <2 x i64> [ <i64 1, i64 2>, %{{.*}} ], [ %[[NVIND:.*]], %[[BLK]] ]
!
! NO-UNROLL-NEXT: %[[IV_D:.*]] = uitofp nneg <2 x i64> %[[VIND]] to <2 x double>
! NO-UNROLL-NEXT: %[[GEP:.*]] = getelementptr double, ptr %[[ARG0]], i64 %[[IND]]
! NO-UNROLL-NEXT: store <2 x double> %[[IV_D]], ptr %[[GEP]]
! NO-UNROLL-NEXT: %[[NIV:.*]] = add nuw i64 %{{.*}}, 2
! NO-UNROLL-NEXT: %[[NVIND]] = add <2 x i64> %[[VIND]], splat (i64 2)
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@kiranchandramohan kiranchandramohan Jan 14, 2025 •
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Unroll should ideally check for the branch back to the body. And nounroll should probably check that there is no such branch?

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@DavidTruby DavidTruby Jan 14, 2025

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-funroll-loops doesn't mean that the loop will be fully unrolled, just that some unrolling can occur. So there's a branch back to the body of the loop in both cases.

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@kiranchandramohan kiranchandramohan Jan 15, 2025

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For small loops, it will fully unroll if the body is small.

The issue with checking for two iterations is that this could be due to interleaving during vectorisation as well.

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@DavidTruby DavidTruby Jan 15, 2025

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I actually did try to only have (e.g.) 2 iterations of the loop; for some reason the full loop is still emitted, at least at -O1. What I ended up with here was essentially copied from the clang -funroll-loops tests but converted to fortran.

!
! UNROLL-NEXT: %[[VIND1:.*]] = add <2 x i64> %[[VIND]], splat (i64 2)
! UNROLL-NEXT: %[[IV0_D:.*]] = uitofp nneg <2 x i64> %[[VIND]] to <2 x double>
! UNROLL-NEXT: %[[IV1_D:.*]] = uitofp nneg <2 x i64> %[[VIND1]] to <2 x double>
! UNROLL-NEXT: %[[GEP0:.*]] = getelementptr double, ptr %[[ARG0]], i64 %[[IND]]
! UNROLL-NEXT: %[[GEP1:.*]] = getelementptr i8, ptr %[[GEP0]], i64 16
! UNROLL-NEXT: store <2 x double> %[[IV0_D]], ptr %[[GEP0]]
! UNROLL-NEXT: store <2 x double> %[[IV1_D]], ptr %[[GEP1]]
! UNROLL-NEXT: %[[NIV:.*]] = add nuw i64 %[[IND]], 4
! UNROLL-NEXT: %[[NVIND:.*]] = add <2 x i64> %[[VIND]], splat (i64 4)
!
! CHECK-NEXT: %[[EXIT:.*]] = icmp eq i64 %[[NIV]], 1000
! CHECK-NEXT: br i1 %[[EXIT]], label %{{.*}}, label %[[BLK]]
do i=1,1000
a(i) = i
end do
end subroutine
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