[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-22 Thread Jan Patrick Lehr via cfe-commits 

https://github.com/jplehr closed https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-19 Thread Jan Patrick Lehr via cfe-commits 

jplehr wrote:

I just realized that I need to update the clang lit tests, so this is *not 
ready to land*, but I don't see a button to indicate that.

https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-19 Thread Jan Patrick Lehr via cfe-commits 

https://github.com/jplehr updated 
https://github.com/llvm/llvm-project/pull/76571

>From 41b227e2c84b3c7eeedb6a9ebf559bec2c34aec3 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Fri, 29 Dec 2023 04:32:24 -0500
Subject: [PATCH] [OpenMP][USM] Introduces -fopenmp-force-usm flag

This flag forces the compiler to generate code for OpenMP target regions
as if the user specified the #pragma omp requires unified_shared_memory
in each source file.

The option does not have a -fno-* friend since OpenMP requires the
unified_shared_memory clause to be present in all source files. Since
this flag does no harm if the clause is present, it can be used in
conjunction. My understanding is that USM should not be turned off
selectively, hence, no -fno- version.

This adds a basic test to check the correct generation of double
indirect access to declare target globals in USM mode vs non-USM mode.
Which I think is the only difference observable in code generation.

This runtime test checks for the (non-)occurence of data movement between host
and device. It does one run without the flag and one with the flag to
also see that both versions behave as expected. In the case w/o the new
flag data movement between host and device is expected. In the case with
the flag such data movement should not be present / reported.
---
 clang/include/clang/Basic/LangOptions.def |  1 +
 clang/include/clang/Driver/Options.td |  4 +
 clang/lib/CodeGen/CGOpenMPRuntime.cpp |  7 ++
 clang/lib/Driver/ToolChains/Clang.cpp |  2 +
 clang/test/OpenMP/force-usm.c | 74 +++
 openmp/libomptarget/test/lit.cfg  |  8 ++
 .../test/offloading/force-usm.cpp | 59 +++
 7 files changed, 155 insertions(+)
 create mode 100644 clang/test/OpenMP/force-usm.c
 create mode 100644 openmp/libomptarget/test/offloading/force-usm.cpp

diff --git a/clang/include/clang/Basic/LangOptions.def 
b/clang/include/clang/Basic/LangOptions.def
index 21abc346cf17ac..81cf2ad9498a7f 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -260,6 +260,7 @@ LANGOPT(OpenMPTeamSubscription  , 1, 0, "Assume distributed 
loops do not have mo
 LANGOPT(OpenMPNoThreadState  , 1, 0, "Assume that no thread in a parallel 
region will modify an ICV.")
 LANGOPT(OpenMPNoNestedParallelism  , 1, 0, "Assume that no thread in a 
parallel region will encounter a parallel region")
 LANGOPT(OpenMPOffloadMandatory  , 1, 0, "Assert that offloading is mandatory 
and do not create a host fallback.")
+LANGOPT(OpenMPForceUSM , 1, 0, "Enable OpenMP unified shared memory mode 
via compiler.")
 LANGOPT(NoGPULib  , 1, 0, "Indicate a build without the standard GPU 
libraries.")
 LANGOPT(RenderScript  , 1, 0, "RenderScript")
 
diff --git a/clang/include/clang/Driver/Options.td 
b/clang/include/clang/Driver/Options.td
index 2b93ddf033499c..28290da438c62d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3451,6 +3451,10 @@ def fopenmp_offload_mandatory : Flag<["-"], 
"fopenmp-offload-mandatory">, Group<
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Do not create a host fallback if offloading to the device fails.">,
   MarshallingInfoFlag>;
+def fopenmp_force_usm : Flag<["-"], "fopenmp-force-usm">, Group,
+  Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Force behvaior as if the user specified pragma omp requires 
unified_shared_memory.">,
+  MarshallingInfoFlag>;
 def fopenmp_target_jit : Flag<["-"], "fopenmp-target-jit">, Group,
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CLOption]>,
   HelpText<"Emit code that can be JIT compiled for OpenMP offloading. Implies 
-foffload-lto=full">;
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp 
b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index ea6645a39e8321..4855e7410a015a 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -1044,6 +1044,13 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule )
  ? CGM.getLangOpts().OMPHostIRFile
  : StringRef{});
   OMPBuilder.setConfig(Config);
+
+  // The user forces the compiler to behave as if omp requires
+  // unified_shared_memory was given.
+  if (CGM.getLangOpts().OpenMPForceUSM) {
+HasRequiresUnifiedSharedMemory = true;
+OMPBuilder.Config.setHasRequiresUnifiedSharedMemory(true);
+  }
 }
 
 void CGOpenMPRuntime::clear() {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index acfa119805068d..ffc24201ab2e0b 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6382,6 +6382,8 @@ void Clang::ConstructJob(Compilation , const JobAction 
,
 CmdArgs.push_back("-fopenmp-assume-no-nested-parallelism");
   if

[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-19 Thread Jan Patrick Lehr via cfe-commits 

jplehr wrote:

> Automatic zero-copy doesn't work on some of the bbot's. I will have to land 
> this once the lit test harness extension in #77851 re-lands.

Having your work landed would be very helpful indeed.

https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-19 Thread via cfe-commits 

carlobertolli wrote:

Automatic zero-copy doesn't work on some of the bbot's. I will have to land 
this once the lit test harness extension in #77851 re-lands.


https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread Jan Patrick Lehr via cfe-commits 

https://github.com/jplehr updated 
https://github.com/llvm/llvm-project/pull/76571

>From bf25a538e7c020efde557b595eba64b804cbb817 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Fri, 29 Dec 2023 04:32:24 -0500
Subject: [PATCH 1/5] [OpenMP][USM] Introduces -fopenmp-force-usm flag

This flag forces the compiler to generate code for OpenMP target regions
as if the user specified the #pragma omp requires unified_shared_memory
in each source file.

The option does not have a -fno-* friend since OpenMP requires the
unified_shared_memory clause to be present in all source files. Since
this flag does no harm if the clause is present, it can be used in
conjunction. My understanding is that USM should not be turned off
selectively, hence, no -fno- version.
---
 clang/include/clang/Basic/LangOptions.def | 1 +
 clang/include/clang/Driver/Options.td | 4 
 clang/lib/CodeGen/CGOpenMPRuntime.cpp | 7 +++
 clang/lib/Driver/ToolChains/Clang.cpp | 2 ++
 4 files changed, 14 insertions(+)

diff --git a/clang/include/clang/Basic/LangOptions.def 
b/clang/include/clang/Basic/LangOptions.def
index 21abc346cf17ac..81cf2ad9498a7f 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -260,6 +260,7 @@ LANGOPT(OpenMPTeamSubscription  , 1, 0, "Assume distributed 
loops do not have mo
 LANGOPT(OpenMPNoThreadState  , 1, 0, "Assume that no thread in a parallel 
region will modify an ICV.")
 LANGOPT(OpenMPNoNestedParallelism  , 1, 0, "Assume that no thread in a 
parallel region will encounter a parallel region")
 LANGOPT(OpenMPOffloadMandatory  , 1, 0, "Assert that offloading is mandatory 
and do not create a host fallback.")
+LANGOPT(OpenMPForceUSM , 1, 0, "Enable OpenMP unified shared memory mode 
via compiler.")
 LANGOPT(NoGPULib  , 1, 0, "Indicate a build without the standard GPU 
libraries.")
 LANGOPT(RenderScript  , 1, 0, "RenderScript")
 
diff --git a/clang/include/clang/Driver/Options.td 
b/clang/include/clang/Driver/Options.td
index 2b93ddf033499c..28290da438c62d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3451,6 +3451,10 @@ def fopenmp_offload_mandatory : Flag<["-"], 
"fopenmp-offload-mandatory">, Group<
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Do not create a host fallback if offloading to the device fails.">,
   MarshallingInfoFlag>;
+def fopenmp_force_usm : Flag<["-"], "fopenmp-force-usm">, Group,
+  Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Force behvaior as if the user specified pragma omp requires 
unified_shared_memory.">,
+  MarshallingInfoFlag>;
 def fopenmp_target_jit : Flag<["-"], "fopenmp-target-jit">, Group,
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CLOption]>,
   HelpText<"Emit code that can be JIT compiled for OpenMP offloading. Implies 
-foffload-lto=full">;
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp 
b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index ea6645a39e8321..4855e7410a015a 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -1044,6 +1044,13 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule )
  ? CGM.getLangOpts().OMPHostIRFile
  : StringRef{});
   OMPBuilder.setConfig(Config);
+
+  // The user forces the compiler to behave as if omp requires
+  // unified_shared_memory was given.
+  if (CGM.getLangOpts().OpenMPForceUSM) {
+HasRequiresUnifiedSharedMemory = true;
+OMPBuilder.Config.setHasRequiresUnifiedSharedMemory(true);
+  }
 }
 
 void CGOpenMPRuntime::clear() {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index acfa119805068d..ffc24201ab2e0b 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6382,6 +6382,8 @@ void Clang::ConstructJob(Compilation , const JobAction 
,
 CmdArgs.push_back("-fopenmp-assume-no-nested-parallelism");
   if (Args.hasArg(options::OPT_fopenmp_offload_mandatory))
 CmdArgs.push_back("-fopenmp-offload-mandatory");
+  if (Args.hasArg(options::OPT_fopenmp_force_usm))
+CmdArgs.push_back("-fopenmp-force-usm");
   break;
 default:
   // By default, if Clang doesn't know how to generate useful OpenMP code

>From 11ad5633889870d897bfc4e77bc41b569e5ce539 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Wed, 12 Jul 2023 05:04:41 -0400
Subject: [PATCH 2/5] [OpenMP][USM] Adds test for -fopenmp-force-usm flag

This adds a basic test to check the correct generation of double
indirect access to declare target globals in USM mode vs non-USM mode.

Marked as XFAIL to first land test and then enable in subsequent patch.
---
 clang/test/OpenMP/force-usm.c | 74 +++
 1 file changed, 74 insertions(+)
 create mode 100644 clang/test/OpenMP/force-usm.c

diff --git

[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread Jan Patrick Lehr via cfe-commits 

https://github.com/jplehr updated 
https://github.com/llvm/llvm-project/pull/76571

>From bf25a538e7c020efde557b595eba64b804cbb817 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Fri, 29 Dec 2023 04:32:24 -0500
Subject: [PATCH 1/4] [OpenMP][USM] Introduces -fopenmp-force-usm flag

This flag forces the compiler to generate code for OpenMP target regions
as if the user specified the #pragma omp requires unified_shared_memory
in each source file.

The option does not have a -fno-* friend since OpenMP requires the
unified_shared_memory clause to be present in all source files. Since
this flag does no harm if the clause is present, it can be used in
conjunction. My understanding is that USM should not be turned off
selectively, hence, no -fno- version.
---
 clang/include/clang/Basic/LangOptions.def | 1 +
 clang/include/clang/Driver/Options.td | 4 
 clang/lib/CodeGen/CGOpenMPRuntime.cpp | 7 +++
 clang/lib/Driver/ToolChains/Clang.cpp | 2 ++
 4 files changed, 14 insertions(+)

diff --git a/clang/include/clang/Basic/LangOptions.def 
b/clang/include/clang/Basic/LangOptions.def
index 21abc346cf17ac3..81cf2ad9498a7f9 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -260,6 +260,7 @@ LANGOPT(OpenMPTeamSubscription  , 1, 0, "Assume distributed 
loops do not have mo
 LANGOPT(OpenMPNoThreadState  , 1, 0, "Assume that no thread in a parallel 
region will modify an ICV.")
 LANGOPT(OpenMPNoNestedParallelism  , 1, 0, "Assume that no thread in a 
parallel region will encounter a parallel region")
 LANGOPT(OpenMPOffloadMandatory  , 1, 0, "Assert that offloading is mandatory 
and do not create a host fallback.")
+LANGOPT(OpenMPForceUSM , 1, 0, "Enable OpenMP unified shared memory mode 
via compiler.")
 LANGOPT(NoGPULib  , 1, 0, "Indicate a build without the standard GPU 
libraries.")
 LANGOPT(RenderScript  , 1, 0, "RenderScript")
 
diff --git a/clang/include/clang/Driver/Options.td 
b/clang/include/clang/Driver/Options.td
index 2b93ddf033499cc..28290da438c62db 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3451,6 +3451,10 @@ def fopenmp_offload_mandatory : Flag<["-"], 
"fopenmp-offload-mandatory">, Group<
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Do not create a host fallback if offloading to the device fails.">,
   MarshallingInfoFlag>;
+def fopenmp_force_usm : Flag<["-"], "fopenmp-force-usm">, Group,
+  Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Force behvaior as if the user specified pragma omp requires 
unified_shared_memory.">,
+  MarshallingInfoFlag>;
 def fopenmp_target_jit : Flag<["-"], "fopenmp-target-jit">, Group,
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CLOption]>,
   HelpText<"Emit code that can be JIT compiled for OpenMP offloading. Implies 
-foffload-lto=full">;
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp 
b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index ea6645a39e83218..4855e7410a015aa 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -1044,6 +1044,13 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule )
  ? CGM.getLangOpts().OMPHostIRFile
  : StringRef{});
   OMPBuilder.setConfig(Config);
+
+  // The user forces the compiler to behave as if omp requires
+  // unified_shared_memory was given.
+  if (CGM.getLangOpts().OpenMPForceUSM) {
+HasRequiresUnifiedSharedMemory = true;
+OMPBuilder.Config.setHasRequiresUnifiedSharedMemory(true);
+  }
 }
 
 void CGOpenMPRuntime::clear() {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index acfa119805068d2..ffc24201ab2e0b5 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6382,6 +6382,8 @@ void Clang::ConstructJob(Compilation , const JobAction 
,
 CmdArgs.push_back("-fopenmp-assume-no-nested-parallelism");
   if (Args.hasArg(options::OPT_fopenmp_offload_mandatory))
 CmdArgs.push_back("-fopenmp-offload-mandatory");
+  if (Args.hasArg(options::OPT_fopenmp_force_usm))
+CmdArgs.push_back("-fopenmp-force-usm");
   break;
 default:
   // By default, if Clang doesn't know how to generate useful OpenMP code

>From 11ad5633889870d897bfc4e77bc41b569e5ce539 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Wed, 12 Jul 2023 05:04:41 -0400
Subject: [PATCH 2/4] [OpenMP][USM] Adds test for -fopenmp-force-usm flag

This adds a basic test to check the correct generation of double
indirect access to declare target globals in USM mode vs non-USM mode.

Marked as XFAIL to first land test and then enable in subsequent patch.
---
 clang/test/OpenMP/force-usm.c | 74 +++
 1 file changed, 74 insertions(+)
 create mode 100644 clang/test/OpenMP/force-usm.c

diff --git

[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread via cfe-commits 

github-actions[bot] wrote:




:warning: C/C++ code formatter, clang-format found issues in your code. 
:warning:



You can test this locally with the following command:


``bash
git-clang-format --diff 90802e652db348fd3218fcbfc3e6ac9e90702acd 
e093db3f1bc432654c2105430f2f647f6d2ab362 -- clang/test/OpenMP/force-usm.c 
openmp/libomptarget/test/offloading/force-usm.cpp 
clang/lib/CodeGen/CGOpenMPRuntime.cpp clang/lib/Driver/ToolChains/Clang.cpp
``





View the diff from clang-format here.


``diff
diff --git a/openmp/libomptarget/test/offloading/force-usm.cpp 
b/openmp/libomptarget/test/offloading/force-usm.cpp
index f51f7e782e..e961f315f8 100644
--- a/openmp/libomptarget/test/offloading/force-usm.cpp
+++ b/openmp/libomptarget/test/offloading/force-usm.cpp
@@ -1,9 +1,11 @@
 // RUN: %libomptarget-compilexx-generic
-// RUN: env LIBOMPTARGET_INFO=32 %libomptarget-run-generic 2>&1 | 
%fcheck-generic --check-prefix=NO-USM
+// RUN: env LIBOMPTARGET_INFO=32 %libomptarget-run-generic 2>&1 |
+// %fcheck-generic --check-prefix=NO-USM
 //
 // RUN: %libomptarget-compilexxx-generic-force-usm
 // RUN: env HSA_XNACK=1 LIBOMPTARGET_INFO=32 \
-// RUN:   %libomptarget-run-generic 2>&1 | %fcheck-generic 
--check-prefix=FORCE-USM
+// RUN:   %libomptarget-run-generic 2>&1 | %fcheck-generic
+// --check-prefix=FORCE-USM
 //
 // UNSUPPORTED: nvptx64-nvidia-cuda
 // UNSUPPORTED: nvptx64-nvidia-cuda-LTO
@@ -11,7 +13,6 @@
 #include 
 #include 
 
-
 int GI;
 #pragma omp declare target
 int *pGI;
@@ -21,10 +22,10 @@ int main(void) {
 
   GI = 0;
 
-  pGI = (int *) malloc(sizeof(int));
+  pGI = (int *)malloc(sizeof(int));
   *pGI = 42;
 
-#pragma omp target map(pGI[:1], GI)
+#pragma omp target map(pGI[ : 1], GI)
   {
 GI = 1;
 *pGI = 2;
@@ -35,11 +36,13 @@ int main(void) {
   return 0;
 }
 
-// NO-USM: omptarget device 0 info: Copying data from host to device, 
HstPtr={{.*}}, TgtPtr={{.*}}, Size=4
-// NO-USM: omptarget device 0 info: Copying data from host to device, 
HstPtr={{.*}}, TgtPtr={{.*}}, Size=4
-// NO-USM: omptarget device 0 info: Copying data from host to device, 
HstPtr={{.*}}, TgtPtr={{.*}}, Size=8, Name=pGI
-// NO-USM: omptarget device 0 info: Copying data from device to host, 
TgtPtr={{.*}}, HstPtr={{.*}}, Size=4
-// NO-USM: omptarget device 0 info: Copying data from device to host, 
TgtPtr={{.*}}, HstPtr={{.*}}, Size=4
-// NO-USM: SUCCESS
+// NO-USM: omptarget device 0 info: Copying data from host to device,
+// HstPtr={{.*}}, TgtPtr={{.*}}, Size=4 NO-USM: omptarget device 0 info: 
Copying
+// data from host to device, HstPtr={{.*}}, TgtPtr={{.*}}, Size=4 NO-USM:
+// omptarget device 0 info: Copying data from host to device, HstPtr={{.*}},
+// TgtPtr={{.*}}, Size=8, Name=pGI NO-USM: omptarget device 0 info: Copying 
data
+// from device to host, TgtPtr={{.*}}, HstPtr={{.*}}, Size=4 NO-USM: omptarget
+// device 0 info: Copying data from device to host, TgtPtr={{.*}},
+// HstPtr={{.*}}, Size=4 NO-USM: SUCCESS
 
 // FORCE-USM: SUCCESS

``




https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread Joseph Huber via cfe-commits 

https://github.com/jhuber6 approved this pull request.


https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread Jan Patrick Lehr via cfe-commits 

jplehr wrote:

While I add some documentation, I'd appreciate feedback especially on the lit 
side of things. I would very much like to rename the pretty happy tripple-X 
workaround for substitution debugging into something sane.

https://github.com/llvm/llvm-project/pull/76571
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[clang] [openmp] [OpenMP][USM] Introduces -fopenmp-force-usm flag (PR #76571)

2024-01-18 Thread Jan Patrick Lehr via cfe-commits 

https://github.com/jplehr updated 
https://github.com/llvm/llvm-project/pull/76571

>From bf25a538e7c020efde557b595eba64b804cbb817 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Fri, 29 Dec 2023 04:32:24 -0500
Subject: [PATCH 1/3] [OpenMP][USM] Introduces -fopenmp-force-usm flag

This flag forces the compiler to generate code for OpenMP target regions
as if the user specified the #pragma omp requires unified_shared_memory
in each source file.

The option does not have a -fno-* friend since OpenMP requires the
unified_shared_memory clause to be present in all source files. Since
this flag does no harm if the clause is present, it can be used in
conjunction. My understanding is that USM should not be turned off
selectively, hence, no -fno- version.
---
 clang/include/clang/Basic/LangOptions.def | 1 +
 clang/include/clang/Driver/Options.td | 4 
 clang/lib/CodeGen/CGOpenMPRuntime.cpp | 7 +++
 clang/lib/Driver/ToolChains/Clang.cpp | 2 ++
 4 files changed, 14 insertions(+)

diff --git a/clang/include/clang/Basic/LangOptions.def 
b/clang/include/clang/Basic/LangOptions.def
index 21abc346cf17ac..81cf2ad9498a7f 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -260,6 +260,7 @@ LANGOPT(OpenMPTeamSubscription  , 1, 0, "Assume distributed 
loops do not have mo
 LANGOPT(OpenMPNoThreadState  , 1, 0, "Assume that no thread in a parallel 
region will modify an ICV.")
 LANGOPT(OpenMPNoNestedParallelism  , 1, 0, "Assume that no thread in a 
parallel region will encounter a parallel region")
 LANGOPT(OpenMPOffloadMandatory  , 1, 0, "Assert that offloading is mandatory 
and do not create a host fallback.")
+LANGOPT(OpenMPForceUSM , 1, 0, "Enable OpenMP unified shared memory mode 
via compiler.")
 LANGOPT(NoGPULib  , 1, 0, "Indicate a build without the standard GPU 
libraries.")
 LANGOPT(RenderScript  , 1, 0, "RenderScript")
 
diff --git a/clang/include/clang/Driver/Options.td 
b/clang/include/clang/Driver/Options.td
index 2b93ddf033499c..28290da438c62d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3451,6 +3451,10 @@ def fopenmp_offload_mandatory : Flag<["-"], 
"fopenmp-offload-mandatory">, Group<
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Do not create a host fallback if offloading to the device fails.">,
   MarshallingInfoFlag>;
+def fopenmp_force_usm : Flag<["-"], "fopenmp-force-usm">, Group,
+  Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CC1Option]>,
+  HelpText<"Force behvaior as if the user specified pragma omp requires 
unified_shared_memory.">,
+  MarshallingInfoFlag>;
 def fopenmp_target_jit : Flag<["-"], "fopenmp-target-jit">, Group,
   Flags<[NoArgumentUnused]>, Visibility<[ClangOption, CLOption]>,
   HelpText<"Emit code that can be JIT compiled for OpenMP offloading. Implies 
-foffload-lto=full">;
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp 
b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index ea6645a39e8321..4855e7410a015a 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -1044,6 +1044,13 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule )
  ? CGM.getLangOpts().OMPHostIRFile
  : StringRef{});
   OMPBuilder.setConfig(Config);
+
+  // The user forces the compiler to behave as if omp requires
+  // unified_shared_memory was given.
+  if (CGM.getLangOpts().OpenMPForceUSM) {
+HasRequiresUnifiedSharedMemory = true;
+OMPBuilder.Config.setHasRequiresUnifiedSharedMemory(true);
+  }
 }
 
 void CGOpenMPRuntime::clear() {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp 
b/clang/lib/Driver/ToolChains/Clang.cpp
index acfa119805068d..ffc24201ab2e0b 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6382,6 +6382,8 @@ void Clang::ConstructJob(Compilation , const JobAction 
,
 CmdArgs.push_back("-fopenmp-assume-no-nested-parallelism");
   if (Args.hasArg(options::OPT_fopenmp_offload_mandatory))
 CmdArgs.push_back("-fopenmp-offload-mandatory");
+  if (Args.hasArg(options::OPT_fopenmp_force_usm))
+CmdArgs.push_back("-fopenmp-force-usm");
   break;
 default:
   // By default, if Clang doesn't know how to generate useful OpenMP code

>From 11ad5633889870d897bfc4e77bc41b569e5ce539 Mon Sep 17 00:00:00 2001
From: JP Lehr 
Date: Wed, 12 Jul 2023 05:04:41 -0400
Subject: [PATCH 2/3] [OpenMP][USM] Adds test for -fopenmp-force-usm flag

This adds a basic test to check the correct generation of double
indirect access to declare target globals in USM mode vs non-USM mode.

Marked as XFAIL to first land test and then enable in subsequent patch.
---
 clang/test/OpenMP/force-usm.c | 74 +++
 1 file changed, 74 insertions(+)
 create mode 100644 clang/test/OpenMP/force-usm.c

diff --git