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[DirectX] Remove unused global variables #149184

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[DirectX] Remove unused global variables #149184

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d063024
remove unused global variables in finalize linkage pass
kmpeng Jul 16, 2025
0fe55a5
change 2 for loops to 1
kmpeng Jul 16, 2025
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8 changes: 8 additions & 0 deletions llvm/lib/Target/DirectX/DXILFinalizeLinkage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,14 @@ static bool finalizeLinkage(Module &M) {
}
}

// Remove unused global variables.
for (GlobalVariable &GV : make_early_inc_range(M.globals())) {
if (GV.use_empty()) {
GV.eraseFromParent();
MadeChange = true;
}
}
Comment on lines +32 to +37
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style nit: unecessary curly braces

Suggested change
for (GlobalVariable &GV : make_early_inc_range(M.globals())) {
if (GV.use_empty()) {
GV.eraseFromParent();
MadeChange = true;
}
}
for (GlobalVariable &GV : make_early_inc_range(M.globals()))
if (GV.use_empty()) {
GV.eraseFromParent();
MadeChange = true;
}


SmallVector<Function *> Funcs;

// Collect non-entry and non-exported functions to set to internal linkage.
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22 changes: 20 additions & 2 deletions llvm/test/CodeGen/DirectX/finalize_linkage.ll
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Original file line number Diff line number Diff line change
@@ -1,10 +1,17 @@
; RUN: opt -S -dxil-finalize-linkage -mtriple=dxil-unknown-shadermodel6.5-compute %s | FileCheck %s
; RUN: llc %s --filetype=asm -o - | FileCheck %s --check-prefixes=CHECK-LLC
; TODO: Add back the llc test once #149179 and #149180 are fixed
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These are fixed now.

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Great, thanks!


target triple = "dxilv1.5-pc-shadermodel6.5-compute"

; DXILFinalizeLinkage changes linkage of all functions that are hidden to
; internal, and converts private global variables to internal linkage.
; internal, converts private global variables to internal linkage, and removes
; unused global variables.

; CHECK-NOT: @aTile
@aTile = hidden addrspace(3) global [4 x [1 x i32]] zeroinitializer, align 4

; CHECK-NOT: @bTile
@bTile = hidden addrspace(3) global [1 x <1 x i32>] zeroinitializer, align 4

; CHECK: @switch.table = internal unnamed_addr constant [4 x i32]
@switch.table = private unnamed_addr constant [4 x i32] [i32 1, i32 257, i32 65793, i32 16843009], align 4
Expand All @@ -27,6 +34,17 @@ target triple = "dxilv1.5-pc-shadermodel6.5-compute"
; CHECK: @hidden_var = hidden global i32
@hidden_var = hidden global i32 1, align 4

define void @anchor_function() #0 {
entry:
%0 = load i32, ptr @switch.table, align 4
%1 = load [3 x float], ptr @private_array, align 4
%2 = load i32, ptr @private_var, align 4
%3 = load i32, ptr @internal_var, align 4
%4 = load i32, ptr @external_var, align 4
%5 = load i32, ptr @hidden_var, align 4
ret void
}

; CHECK-NOT: define internal void @"?f1@@YAXXZ"()
define void @"?f1@@YAXXZ"() #0 {
entry:
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/DirectX/scalar-data.ll
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@@ -1,4 +1,4 @@
; RUN: llc %s -mtriple=dxil-pc-shadermodel6.3-library --filetype=asm -o - | FileCheck %s
; RUN: opt -S -passes='dxil-data-scalarization,dxil-flatten-arrays' -mtriple=dxil-unknown-shadermodel6.5-compute %s | FileCheck %s

; Make sure we don't touch arrays without vectors and that can recurse and flatten multiple-dimension arrays of vectors

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