[llvm] [RISCV] Enable global merging by default (PR #115495)
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Fri Nov 8 07:00:55 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Alex Bradbury (asb)
<details>
<summary>Changes</summary>
Stacks on top of <https://github.com/llvm/llvm-project/pull/115484>.
>From the discussion at the round-table at the RISC-V Summit it was clear
people see cases where global merging would help. So the direction of
enabling it by default and iteratively working to enable it in more
cases or to improve the heuristics seems sensible. This patch tries to
make a minimal step in that direction.
---
Full diff: https://github.com/llvm/llvm-project/pull/115495.diff
7 Files Affected:
- (modified) llvm/lib/Target/RISCV/RISCVTargetMachine.cpp (+16-2)
- (modified) llvm/test/CodeGen/RISCV/O3-pipeline.ll (+1)
- (modified) llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll (+5-4)
- (modified) llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll (+5-4)
- (modified) llvm/test/CodeGen/RISCV/global-merge-minsize.ll (+4-4)
- (modified) llvm/test/CodeGen/RISCV/global-merge-offset.ll (+8-8)
- (modified) llvm/test/CodeGen/RISCV/global-merge.ll (+22-6)
``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
index a5afbcfd79710f..4fc185525d8d25 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
@@ -53,6 +53,13 @@ static cl::opt<cl::boolOrDefault>
EnableGlobalMerge("riscv-enable-global-merge", cl::Hidden,
cl::desc("Enable the global merge pass"));
+static cl::opt<bool> ForceEnableGlobalMergeExternalGlobals(
+ "riscv-force-enable-global-merge-external-globals", cl::Hidden,
+ cl::init(false),
+ cl::desc(
+ "If the global merge pass is enabled, force enable global merging of "
+ "external globals (overriding any logic that might disable it)"));
+
static cl::opt<bool>
EnableMachineCombiner("riscv-enable-machine-combiner",
cl::desc("Enable the machine combiner pass"),
@@ -469,10 +476,17 @@ bool RISCVPassConfig::addPreISel() {
addPass(createBarrierNoopPass());
}
- if (EnableGlobalMerge == cl::BOU_TRUE) {
+ if ((TM->getOptLevel() != CodeGenOptLevel::None &&
+ EnableGlobalMerge == cl::BOU_UNSET) ||
+ EnableGlobalMerge == cl::BOU_TRUE) {
+ // FIXME: Like AArch64, we disable extern global merging by default due to
+ // concerns it might regress some workloads. Unlike AArch64, we don't
+ // currently support enabling the pass in an "OnlyOptimizeForSize" mode.
+ // Investigating and addressing both items are TODO.
addPass(createGlobalMergePass(TM, /* MaxOffset */ 2047,
/* OnlyOptimizeForSize */ false,
- /* MergeExternalByDefault */ true));
+ /* MergeExternalByDefault */
+ ForceEnableGlobalMergeExternalGlobals));
}
return false;
diff --git a/llvm/test/CodeGen/RISCV/O3-pipeline.ll b/llvm/test/CodeGen/RISCV/O3-pipeline.ll
index a74c842c595526..8fd9ae98503665 100644
--- a/llvm/test/CodeGen/RISCV/O3-pipeline.ll
+++ b/llvm/test/CodeGen/RISCV/O3-pipeline.ll
@@ -74,6 +74,7 @@
; CHECK-NEXT: Exception handling preparation
; CHECK-NEXT: A No-Op Barrier Pass
; CHECK-NEXT: FunctionPass Manager
+; CHECK-NEXT: Merge internal globals
; CHECK-NEXT: Dominator Tree Construction
; CHECK-NEXT: Basic Alias Analysis (stateless AA impl)
; CHECK-NEXT: Function Alias Analysis Results
diff --git a/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll b/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll
index c5471389302124..156a34db827456 100644
--- a/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll
+++ b/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll
@@ -1,8 +1,9 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -verify-machineinstrs < %s \
-; RUN: | FileCheck %s -check-prefix=SMALL-DATA
-; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=0 \
-; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=MINSIZE
+; RUN: llc -mtriple=riscv64 -riscv-force-enable-global-merge-external-globals \
+; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=SMALL-DATA
+; RUN: llc -mtriple=riscv64 -global-merge-min-data-size=0 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
+; RUN: | FileCheck %s -check-prefix=MINSIZE
@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4
diff --git a/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll b/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll
index 8e4d72af00ebce..e41f14d394b7ca 100644
--- a/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll
+++ b/llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll
@@ -1,8 +1,9 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
-; RUN: | FileCheck %s -check-prefix=SMALL-DATA
-; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=5 \
-; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=MINSIZE
+; RUN: llc -mtriple=riscv32 -riscv-force-enable-global-merge-external-globals \
+; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=SMALL-DATA
+; RUN: llc -mtriple=riscv64 -global-merge-min-data-size=5 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
+; RUN: | FileCheck %s -check-prefix=MINSIZE
@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4
diff --git a/llvm/test/CodeGen/RISCV/global-merge-minsize.ll b/llvm/test/CodeGen/RISCV/global-merge-minsize.ll
index e405425832acbb..1d65d9d1732ba3 100644
--- a/llvm/test/CodeGen/RISCV/global-merge-minsize.ll
+++ b/llvm/test/CodeGen/RISCV/global-merge-minsize.ll
@@ -1,8 +1,8 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
-; RUN: | FileCheck %s -check-prefix=RV32
-; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -global-merge-min-data-size=5 \
-; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32-MINSIZE
+; RUN: llc -mtriple=riscv32 -riscv-force-enable-global-merge-external-globals \
+; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32
+; RUN: llc -mtriple=riscv32 -global-merge-min-data-size=5 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32-MINSIZE
@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4
diff --git a/llvm/test/CodeGen/RISCV/global-merge-offset.ll b/llvm/test/CodeGen/RISCV/global-merge-offset.ll
index 13afcba181719e..bb8264ee438545 100644
--- a/llvm/test/CodeGen/RISCV/global-merge-offset.ll
+++ b/llvm/test/CodeGen/RISCV/global-merge-offset.ll
@@ -1,12 +1,12 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv32 -riscv-enable-global-merge \
-; RUN: -verify-machineinstrs | FileCheck %s
-; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv64 -riscv-enable-global-merge \
-; RUN: -verify-machineinstrs | FileCheck %s
-; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv32 -riscv-enable-global-merge \
-; RUN: -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
-; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv64 -riscv-enable-global-merge \
-; RUN: -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
+; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv32 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s
+; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv64 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s
+; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv32 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
+; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv64 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
; This test demonstrates that the MaxOffset is set correctly for RISC-V by
; constructing an input that is at the limit and comparing.
diff --git a/llvm/test/CodeGen/RISCV/global-merge.ll b/llvm/test/CodeGen/RISCV/global-merge.ll
index 20379ee2e7dacd..8b4043ed476f77 100644
--- a/llvm/test/CodeGen/RISCV/global-merge.ll
+++ b/llvm/test/CodeGen/RISCV/global-merge.ll
@@ -1,8 +1,12 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
-; RUN: | FileCheck %s
-; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -verify-machineinstrs < %s \
-; RUN: | FileCheck %s
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s | FileCheck %s
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s | FileCheck %s
+; RUN: llc -mtriple=riscv32 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=CHECK-WEXTERN %s
+; RUN: llc -mtriple=riscv64 \
+; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
+; RUN: | FileCheck -check-prefix=CHECK-WEXTERN %s
@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4
@@ -21,9 +25,21 @@ define void @f1(i32 %a) nounwind {
; CHECK-NEXT: sw a0, %lo(.L_MergedGlobals)(a1)
; CHECK-NEXT: addi a1, a1, %lo(.L_MergedGlobals)
; CHECK-NEXT: sw a0, 4(a1)
-; CHECK-NEXT: sw a0, 8(a1)
-; CHECK-NEXT: sw a0, 12(a1)
+; CHECK-NEXT: lui a1, %hi(eg1)
+; CHECK-NEXT: sw a0, %lo(eg1)(a1)
+; CHECK-NEXT: lui a1, %hi(eg2)
+; CHECK-NEXT: sw a0, %lo(eg2)(a1)
; CHECK-NEXT: ret
+;
+; CHECK-WEXTERN-LABEL: f1:
+; CHECK-WEXTERN: # %bb.0:
+; CHECK-WEXTERN-NEXT: lui a1, %hi(.L_MergedGlobals)
+; CHECK-WEXTERN-NEXT: sw a0, %lo(.L_MergedGlobals)(a1)
+; CHECK-WEXTERN-NEXT: addi a1, a1, %lo(.L_MergedGlobals)
+; CHECK-WEXTERN-NEXT: sw a0, 4(a1)
+; CHECK-WEXTERN-NEXT: sw a0, 8(a1)
+; CHECK-WEXTERN-NEXT: sw a0, 12(a1)
+; CHECK-WEXTERN-NEXT: ret
store i32 %a, ptr @ig1, align 4
store i32 %a, ptr @ig2, align 4
store i32 %a, ptr @eg1, align 4
``````````
</details>
https://github.com/llvm/llvm-project/pull/115495
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