[flang-commits] [flang] [flang] Correctly handle `!dir$ unroll` with unrolling factors of 0 and 1 (PR #126170)
Asher Mancinelli via flang-commits
flang-commits at lists.llvm.org
Sun Feb 9 07:45:43 PST 2025
https://github.com/ashermancinelli updated https://github.com/llvm/llvm-project/pull/126170
>From 8cf8f527fec3a8b1018e9507b864330f07fe98f4 Mon Sep 17 00:00:00 2001
From: Asher Mancinelli <ashermancinelli at gmail.com>
Date: Thu, 6 Feb 2025 17:14:22 -0800
Subject: [PATCH] [flang] Handle !dir$ unroll [01]
When an explicit `N` is passed to the loop unroll directive, the
unrolling factor should N if N > 1, and unrolling should be disabled
when N is 0 or 1. Update docs and add test cases.
---
flang/docs/Directives.md | 9 +++++-
flang/lib/Lower/Bridge.cpp | 47 +++++++++++++++++++++++--------
flang/test/Integration/unroll.f90 | 45 +++++++++++++++++++++++++----
3 files changed, 82 insertions(+), 19 deletions(-)
diff --git a/flang/docs/Directives.md b/flang/docs/Directives.md
index f356f762b13a2d2..c6c2e29a420ea9d 100644
--- a/flang/docs/Directives.md
+++ b/flang/docs/Directives.md
@@ -39,15 +39,22 @@ A list of non-standard directives supported by Flang
* `!dir$ vector always` forces vectorization on the following loop regardless
of cost model decisions. The loop must still be vectorizable.
[This directive currently only works on plain do loops without labels].
+* `!dir$ unroll [n]` specifies that the compiler ought to unroll the immediately
+ following loop `n` times. When `n` is `0` or `1`, the loop should not be unrolled
+ at all. When `n` is `2` or greater, the loop should be unrolled exactly `n`
+ times if possible. When `n` is omitted, the compiler should attempt to fully
+ unroll the loop. Some compilers accept an optional `=` before the `n` when `n`
+ is present in the directive. Flang does not.
# Directive Details
## Introduction
Directives are commonly used in Fortran programs to specify additional actions
to be performed by the compiler. The directives are always specified with the
-`!dir$` or `cdir$` prefix.
+`!dir$` or `cdir$` prefix.
## Loop Directives
+
Some directives are associated with the following construct, for example loop
directives. Directives on loops are used to specify additional transformation to
be performed by the compiler like enabling vectorisation, unrolling, interchange
diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index a31629b17cf295e..36e58e456dea350 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -63,6 +63,7 @@
#include "flang/Semantics/tools.h"
#include "flang/Support/Version.h"
#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
+#include "mlir/IR/BuiltinAttributes.h"
#include "mlir/IR/Matchers.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Parser/Parser.h"
@@ -2170,11 +2171,38 @@ class FirConverter : public Fortran::lower::AbstractConverter {
return builder->createIntegerConstant(loc, controlType, 1); // step
}
+ // For unroll directives without a value, force full unrolling.
+ // For unroll directives with a value, if the value is greater than 1,
+ // force unrolling with the given factor. Otherwise, disable unrolling.
+ mlir::LLVM::LoopUnrollAttr
+ genLoopUnrollAttr(std::optional<std::uint64_t> directiveArg) {
+ mlir::BoolAttr falseAttr =
+ mlir::BoolAttr::get(builder->getContext(), false);
+ mlir::BoolAttr trueAttr = mlir::BoolAttr::get(builder->getContext(), true);
+ mlir::IntegerAttr countAttr;
+ mlir::BoolAttr fullUnrollAttr;
+ bool shouldUnroll = true;
+ if (directiveArg.has_value()) {
+ auto unrollingFactor = directiveArg.value();
+ if (unrollingFactor == 0 || unrollingFactor == 1) {
+ shouldUnroll = false;
+ } else {
+ countAttr =
+ builder->getIntegerAttr(builder->getI64Type(), unrollingFactor);
+ }
+ } else {
+ fullUnrollAttr = trueAttr;
+ }
+
+ mlir::BoolAttr disableAttr = shouldUnroll ? falseAttr : trueAttr;
+ return mlir::LLVM::LoopUnrollAttr::get(
+ builder->getContext(), /*disable=*/disableAttr, /*count=*/countAttr, {},
+ /*full=*/fullUnrollAttr, {}, {}, {});
+ }
+
void addLoopAnnotationAttr(
IncrementLoopInfo &info,
llvm::SmallVectorImpl<const Fortran::parser::CompilerDirective *> &dirs) {
- mlir::BoolAttr f = mlir::BoolAttr::get(builder->getContext(), false);
- mlir::BoolAttr t = mlir::BoolAttr::get(builder->getContext(), true);
mlir::LLVM::LoopVectorizeAttr va;
mlir::LLVM::LoopUnrollAttr ua;
bool has_attrs = false;
@@ -2182,20 +2210,15 @@ class FirConverter : public Fortran::lower::AbstractConverter {
Fortran::common::visit(
Fortran::common::visitors{
[&](const Fortran::parser::CompilerDirective::VectorAlways &) {
+ mlir::BoolAttr falseAttr =
+ mlir::BoolAttr::get(builder->getContext(), false);
va = mlir::LLVM::LoopVectorizeAttr::get(builder->getContext(),
- /*disable=*/f, {}, {},
- {}, {}, {}, {});
+ /*disable=*/falseAttr,
+ {}, {}, {}, {}, {}, {});
has_attrs = true;
},
[&](const Fortran::parser::CompilerDirective::Unroll &u) {
- mlir::IntegerAttr countAttr;
- if (u.v.has_value()) {
- countAttr = builder->getIntegerAttr(builder->getI64Type(),
- u.v.value());
- }
- ua = mlir::LLVM::LoopUnrollAttr::get(
- builder->getContext(), /*disable=*/f, /*count*/ countAttr,
- {}, /*full*/ u.v.has_value() ? f : t, {}, {}, {});
+ ua = genLoopUnrollAttr(u.v);
has_attrs = true;
},
[&](const auto &) {}},
diff --git a/flang/test/Integration/unroll.f90 b/flang/test/Integration/unroll.f90
index 9d69605e10d1b3c..aa47e465b63fceb 100644
--- a/flang/test/Integration/unroll.f90
+++ b/flang/test/Integration/unroll.f90
@@ -3,14 +3,47 @@
! CHECK-LABEL: unroll_dir
subroutine unroll_dir
integer :: a(10)
- !dir$ unroll
- ! CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[ANNOTATION:.*]]
+ !dir$ unroll
+ ! CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[UNROLL_ENABLE_FULL_ANNO:.*]]
do i=1,10
- a(i)=i
+ a(i)=i
end do
end subroutine unroll_dir
-! CHECK: ![[ANNOTATION]] = distinct !{![[ANNOTATION]], ![[UNROLL:.*]], ![[UNROLL_FULL:.*]]}
-! CHECK: ![[UNROLL]] = !{!"llvm.loop.unroll.enable"}
-! CHECK: ![[UNROLL_FULL]] = !{!"llvm.loop.unroll.full"}
+! CHECK-LABEL: unroll_dir_0
+subroutine unroll_dir_0
+ integer :: a(10)
+ !dir$ unroll 0
+ ! CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[UNROLL_DISABLE_ANNO:.*]]
+ do i=1,10
+ a(i)=i
+ end do
+end subroutine unroll_dir_0
+
+! CHECK-LABEL: unroll_dir_1
+subroutine unroll_dir_1
+ integer :: a(10)
+ !dir$ unroll 1
+ ! CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[UNROLL_DISABLE_ANNO]]
+ do i=1,10
+ a(i)=i
+ end do
+end subroutine unroll_dir_1
+
+! CHECK-LABEL: unroll_dir_2
+subroutine unroll_dir_2
+ integer :: a(10)
+ !dir$ unroll 2
+ ! CHECK: br i1 {{.*}}, label {{.*}}, label {{.*}}, !llvm.loop ![[UNROLL_ENABLE_COUNT_2:.*]]
+ do i=1,10
+ a(i)=i
+ end do
+end subroutine unroll_dir_2
+! CHECK: ![[UNROLL_ENABLE_FULL_ANNO]] = distinct !{![[UNROLL_ENABLE_FULL_ANNO]], ![[UNROLL_ENABLE:.*]], ![[UNROLL_FULL:.*]]}
+! CHECK: ![[UNROLL_ENABLE:.*]] = !{!"llvm.loop.unroll.enable"}
+! CHECK: ![[UNROLL_FULL:.*]] = !{!"llvm.loop.unroll.full"}
+! CHECK: ![[UNROLL_DISABLE_ANNO]] = distinct !{![[UNROLL_DISABLE_ANNO]], ![[UNROLL_DISABLE:.*]]}
+! CHECK: ![[UNROLL_DISABLE]] = !{!"llvm.loop.unroll.disable"}
+! CHECK: ![[UNROLL_ENABLE_COUNT_2]] = distinct !{![[UNROLL_ENABLE_COUNT_2]], ![[UNROLL_ENABLE]], ![[UNROLL_COUNT_2:.*]]}
+! CHECK: ![[UNROLL_COUNT_2]] = !{!"llvm.loop.unroll.count", i32 2}
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