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Pierre-vhIanWood1
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IanWood1
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[AMDGPU][SplitModule] Do not create empty modules (llvm#135761)
Skip creating a module if no function is going to be imported. Also includes a change so that if the first partition is empty (which can happen), we import global with non-local linkage into the first non-empty partition, instead of P0 all the time. I thought we'd need to change users of the SplitModule callback so they can deal with less modules than the number requested, but no. We already return only 1 module in some cases and it seems to be handled just fine. Fixes SWDEV-523146
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-34
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6 files changed

+63
-34
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‎llvm/include/llvm/Target/TargetMachine.h‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -451,6 +451,9 @@ class TargetMachine {
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/// Entry point for module splitting. Targets can implement custom module
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/// splitting logic, mainly used by LTO for --lto-partitions.
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///
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/// On success, this guarantees that between 1 and \p NumParts modules were
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/// created and passed to \p ModuleCallBack.
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///
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/// \returns `true` if the module was split, `false` otherwise. When `false`
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/// is returned, it is assumed that \p ModuleCallback has never been called
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/// and \p M has not been modified.

‎llvm/lib/Target/AMDGPU/AMDGPUSplitModule.cpp‎

Lines changed: 15 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1479,6 +1479,10 @@ static void splitAMDGPUModule(
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<< "' - Partition summaries will not be printed\n";
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}
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// One module will import all GlobalValues that are not Functions
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// and are not subject to conservative import.
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bool ImportAllGVs = true;
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for (unsigned PID = 0; PID < NumParts; ++PID) {
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SplitModuleTimer SMT2("modules_creation",
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"creating modules for each partition");
@@ -1488,6 +1492,13 @@ static void splitAMDGPUModule(
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for (unsigned NodeID : (*Proposal)[PID].set_bits())
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FnsInPart.insert(&SG.getNode(NodeID).getFunction());
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// Don't create empty modules.
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if (FnsInPart.empty()) {
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LLVM_DEBUG(dbgs() << "[split] P" << PID
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<< " is empty, not creating module\n");
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continue;
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}
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14911502
ValueToValueMapTy VMap;
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CostType PartCost = 0;
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std::unique_ptr<Module> MPart(
@@ -1501,10 +1512,12 @@ static void splitAMDGPUModule(
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return false;
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}
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1504-
// Everything else goes in the first partition.
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return needsConservativeImport(GV) || PID == 0;
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// Everything else goes in the first non-empty module we create.
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return ImportAllGVs || needsConservativeImport(GV);
15061517
}));
15071518

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ImportAllGVs = false;
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// FIXME: Aliases aren't seen often, and their handling isn't perfect so
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// bugs are possible.
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‎llvm/test/tools/llvm-split/AMDGPU/address-taken-externalize-with-call.ll‎

Lines changed: 4 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,6 @@
11
; RUN: llvm-split -o %t %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-large-threshold=0
22
; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 --implicit-check-not=define %s
33
; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 --implicit-check-not=define %s
4-
; RUN: llvm-dis -o - %t2 | FileCheck --check-prefix=CHECK2 --implicit-check-not=define %s
54

65
; 3 kernels:
76
; - A does a direct call to HelperA
@@ -11,14 +10,11 @@
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; The helper functions will get externalized, so C/A will end up
1211
; in the same partition.
1312

14-
; P0 is empty.
15-
; CHECK0: declare
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; CHECK0: define amdgpu_kernel void @B(ptr %dst)
1614

17-
; CHECK1: define amdgpu_kernel void @B(ptr %dst)
18-
19-
; CHECK2: define hidden void @HelperA()
20-
; CHECK2: define amdgpu_kernel void @A()
21-
; CHECK2: define amdgpu_kernel void @C()
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; CHECK1: define hidden void @HelperA()
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; CHECK1: define amdgpu_kernel void @A()
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; CHECK1: define amdgpu_kernel void @C()
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2319
define internal void @HelperA() {
2420
ret void

‎llvm/test/tools/llvm-split/AMDGPU/large-kernels-merging-weak_odr.ll‎

Lines changed: 10 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,6 @@
11
; RUN: llvm-split -o %t %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-max-depth=0 -amdgpu-module-splitting-large-threshold=1.2 -amdgpu-module-splitting-merge-threshold=0.5
22
; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 --implicit-check-not=define %s
33
; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 --implicit-check-not=define %s
4-
; RUN: llvm-dis -o - %t2 | FileCheck --check-prefix=CHECK2 --implicit-check-not=define %s
54

65
; RUN: llvm-split -o %t.nolarge %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-large-threshold=0 -amdgpu-module-splitting-max-depth=0
76
; RUN: llvm-dis -o - %t.nolarge0 | FileCheck --check-prefix=NOLARGEKERNELS-CHECK0 --implicit-check-not=define %s
@@ -15,19 +14,18 @@
1514
; Also check w/o large kernels processing to verify they are indeed handled
1615
; differently.
1716

18-
; P0 is empty
19-
; CHECK0: declare
17+
; Only two partitions created for the first command.
2018

21-
; CHECK1: define internal void @HelperC()
22-
; CHECK1: define weak_odr amdgpu_kernel void @C
19+
; CHECK0: define internal void @HelperC()
20+
; CHECK0: define weak_odr amdgpu_kernel void @C
2321

24-
; CHECK2: define internal void @large2()
25-
; CHECK2: define internal void @large1()
26-
; CHECK2: define internal void @large0()
27-
; CHECK2: define internal void @HelperA()
28-
; CHECK2: define internal void @HelperB()
29-
; CHECK2: define amdgpu_kernel void @A
30-
; CHECK2: define weak_odr amdgpu_kernel void @B
22+
; CHECK1: define internal void @large2()
23+
; CHECK1: define internal void @large1()
24+
; CHECK1: define internal void @large0()
25+
; CHECK1: define internal void @HelperA()
26+
; CHECK1: define internal void @HelperB()
27+
; CHECK1: define amdgpu_kernel void @A
28+
; CHECK1: define weak_odr amdgpu_kernel void @B
3129

3230
; NOLARGEKERNELS-CHECK0: define internal void @HelperC()
3331
; NOLARGEKERNELS-CHECK0: define weak_odr amdgpu_kernel void @C

‎llvm/test/tools/llvm-split/AMDGPU/large-kernels-merging.ll‎

Lines changed: 10 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,6 @@
11
; RUN: llvm-split -o %t %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-max-depth=0 -amdgpu-module-splitting-large-threshold=1.2 -amdgpu-module-splitting-merge-threshold=0.5
22
; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 --implicit-check-not=define %s
33
; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 --implicit-check-not=define %s
4-
; RUN: llvm-dis -o - %t2 | FileCheck --check-prefix=CHECK2 --implicit-check-not=define %s
54

65
; RUN: llvm-split -o %t.nolarge %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-large-threshold=0 -amdgpu-module-splitting-max-depth=0
76
; RUN: llvm-dis -o - %t.nolarge0 | FileCheck --check-prefix=NOLARGEKERNELS-CHECK0 --implicit-check-not=define %s
@@ -15,19 +14,18 @@
1514
; Also check w/o large kernels processing to verify they are indeed handled
1615
; differently.
1716

18-
; P0 is empty
19-
; CHECK0: declare
17+
; Only 2 partitions for the first command.
2018

21-
; CHECK1: define internal void @HelperC()
22-
; CHECK1: define amdgpu_kernel void @C
19+
; CHECK0: define internal void @HelperC()
20+
; CHECK0: define amdgpu_kernel void @C
2321

24-
; CHECK2: define internal void @large2()
25-
; CHECK2: define internal void @large1()
26-
; CHECK2: define internal void @large0()
27-
; CHECK2: define internal void @HelperA()
28-
; CHECK2: define internal void @HelperB()
29-
; CHECK2: define amdgpu_kernel void @A
30-
; CHECK2: define amdgpu_kernel void @B
22+
; CHECK1: define internal void @large2()
23+
; CHECK1: define internal void @large1()
24+
; CHECK1: define internal void @large0()
25+
; CHECK1: define internal void @HelperA()
26+
; CHECK1: define internal void @HelperB()
27+
; CHECK1: define amdgpu_kernel void @A
28+
; CHECK1: define amdgpu_kernel void @B
3129

3230
; NOLARGEKERNELS-CHECK0: define internal void @HelperC()
3331
; NOLARGEKERNELS-CHECK0: define amdgpu_kernel void @C

‎llvm/test/tools/llvm-split/AMDGPU/preserve-globals.ll‎

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,21 @@
1+
; RUN: llvm-split -o %t %s -j 3 -mtriple amdgcn-amd-amdhsa -amdgpu-module-splitting-max-depth=0 -amdgpu-module-splitting-large-threshold=1.2 -amdgpu-module-splitting-merge-threshold=0.5
2+
; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 --implicit-check-not=define %s
3+
; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 --implicit-check-not=define %s
4+
5+
; Only 2 out of 3 partitions are created, check the external global is preserved in the first partition.
6+
7+
; CHECK0: @foobar = linkonce_odr global i64 52
8+
; CHECK0: define amdgpu_kernel void @B
9+
10+
; CHECK1-NOT: @foobar = linkonce_odr global i64 52
11+
; CHECK1: define amdgpu_kernel void @A
12+
13+
@foobar = linkonce_odr global i64 52
14+
15+
define amdgpu_kernel void @A() {
16+
ret void
17+
}
18+
19+
define amdgpu_kernel void @B() {
20+
ret void
21+
}

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