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[RISCV] Enable global merging by default
Stacks on top of <llvm#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.
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7 files changed

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‎llvm/lib/Target/RISCV/RISCVTargetMachine.cpp

Lines changed: 7 additions & 1 deletion
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@@ -476,7 +476,13 @@ bool RISCVPassConfig::addPreISel() {
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addPass(createBarrierNoopPass());
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}
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479-
if (EnableGlobalMerge == cl::BOU_TRUE) {
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if ((TM->getOptLevel() != CodeGenOptLevel::None &&
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EnableGlobalMerge == cl::BOU_UNSET) ||
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EnableGlobalMerge == cl::BOU_TRUE) {
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// FIXME: Like AArch64, we disable extern global merging by default due to
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// concerns it might regress some workloads. Unlike AArch64, we don't
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// currently support enabling the pass in an "OnlyOptimizeForSize" mode.
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// Investigating and addressing both items are TODO.
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addPass(createGlobalMergePass(TM, /* MaxOffset */ 2047,
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/* OnlyOptimizeForSize */ false,
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/* MergeExternalByDefault */

‎llvm/test/CodeGen/RISCV/O3-pipeline.ll

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@@ -74,6 +74,7 @@
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; CHECK-NEXT: Exception handling preparation
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; CHECK-NEXT: A No-Op Barrier Pass
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; CHECK-NEXT: FunctionPass Manager
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; CHECK-NEXT: Merge internal globals
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; CHECK-NEXT: Dominator Tree Construction
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; CHECK-NEXT: Basic Alias Analysis (stateless AA impl)
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; CHECK-NEXT: Function Alias Analysis Results

‎llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll

Lines changed: 2 additions & 2 deletions
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@@ -1,7 +1,7 @@
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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
2-
; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -riscv-force-enable-global-merge-external-globals \
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; RUN: llc -mtriple=riscv64 -riscv-force-enable-global-merge-external-globals \
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; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=SMALL-DATA
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; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=0 \
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; RUN: llc -mtriple=riscv64 -global-merge-min-data-size=0 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
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; RUN: | FileCheck %s -check-prefix=MINSIZE
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‎llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -riscv-force-enable-global-merge-external-globals \
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; RUN: llc -mtriple=riscv32 -riscv-force-enable-global-merge-external-globals \
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; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=SMALL-DATA
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; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=5 \
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; RUN: llc -mtriple=riscv64 -global-merge-min-data-size=5 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
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; RUN: | FileCheck %s -check-prefix=MINSIZE
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‎llvm/test/CodeGen/RISCV/global-merge-minsize.ll

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -riscv-force-enable-global-merge-external-globals \
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; RUN: llc -mtriple=riscv32 -riscv-force-enable-global-merge-external-globals \
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; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32
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; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -global-merge-min-data-size=5 \
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; RUN: llc -mtriple=riscv32 -global-merge-min-data-size=5 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32-MINSIZE
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@ig1 = internal global i32 0, align 4

‎llvm/test/CodeGen/RISCV/global-merge-offset.ll

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@@ -1,11 +1,11 @@
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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
2-
; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv32 -riscv-enable-global-merge \
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; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv32 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s
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; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv64 -riscv-enable-global-merge \
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; RUN: sed 's/ArrSize/100/g' %s | llc -mtriple=riscv64 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s
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; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv32 -riscv-enable-global-merge \
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; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv32 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
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; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv64 -riscv-enable-global-merge \
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; RUN: sed 's/ArrSize/101/g' %s | llc -mtriple=riscv64 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs | FileCheck %s -check-prefix=CHECK-TOOBIG
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1111
; This test demonstrates that the MaxOffset is set correctly for RISC-V by

‎llvm/test/CodeGen/RISCV/global-merge.ll

Lines changed: 4 additions & 6 deletions
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@@ -1,12 +1,10 @@
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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
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; RUN: | FileCheck %s
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; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -verify-machineinstrs < %s \
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; RUN: | FileCheck %s
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; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge \
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; RUN: llc -mtriple=riscv32 -verify-machineinstrs < %s | FileCheck %s
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; RUN: llc -mtriple=riscv64 -verify-machineinstrs < %s | FileCheck %s
4+
; RUN: llc -mtriple=riscv32 \
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; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
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; RUN: | FileCheck -check-prefix=CHECK-WEXTERN %s
9-
; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge \
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; RUN: llc -mtriple=riscv64 \
108
; RUN: -riscv-force-enable-global-merge-external-globals -verify-machineinstrs < %s \
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; RUN: | FileCheck -check-prefix=CHECK-WEXTERN %s
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