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Do not remove empty basic blocks which have address taken. #67740

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Merged
merged 1 commit into from
Oct 3, 2023
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Do not remove empty basic blocks which have address taken. #67740

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2 changes: 1 addition & 1 deletion llvm/lib/CodeGen/GCEmptyBasicBlocks.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ bool GCEmptyBasicBlocks::runOnMachineFunction(MachineFunction &MF) {
// TODO If a block is an eh pad, or it has address taken, we don't remove
// it. Removing such blocks is possible, but it probably requires a more
// complex logic.
if (MBB->isEHPad() || MBB->isMachineBlockAddressTaken())
if (MBB->isEHPad() || MBB->hasAddressTaken())
continue;
// Skip blocks with real code.
bool HasAnyRealCode = llvm::any_of(*MBB, [](const MachineInstr &MI) {
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31 changes: 26 additions & 5 deletions llvm/test/CodeGen/X86/gc-empty-basic-blocks.ll
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
;; This test verifies that -gc-empty-basic-blocks removes empty blocks.
;; This test verifies that -gc-empty-basic-blocks removes regular empty blocks
;; but does not remove empty blocks which have their address taken.
; RUN: llc < %s -mtriple=x86_64 -O0 -gc-empty-basic-blocks | FileCheck %s

;; This function has a regular empty block.
define void @foo(i1 zeroext %0) nounwind {
br i1 %0, label %2, label %empty_block

Expand All @@ -10,7 +12,7 @@ define void @foo(i1 zeroext %0) nounwind {
; CHECK-NEXT: jmp .LBB0_3

2: ; preds = %1
%3 = call i32 @bar()
%3 = call i32 @baz()
br label %4

; CHECK-LABEL: .LBB0_1:
Expand All @@ -19,8 +21,8 @@ define void @foo(i1 zeroext %0) nounwind {
empty_block: ; preds = %1
unreachable

; CHECK-NOT: %empty_block
; CHECK-NOT: .LBB0_2
; CHECK-NOT: %empty_block
; CHECK-NOT: .LBB0_2

4: ; preds = %2, %empty_block
ret void
Expand All @@ -30,4 +32,23 @@ empty_block: ; preds = %1

}

declare i32 @bar()
;; This function has an empty block which has its address taken. Check that it
;; is not removed by -gc-empty-basic-blocks.
define void @bar(i1 zeroext %0) nounwind {
entry:
%1 = select i1 %0, ptr blockaddress(@bar, %empty_block), ptr blockaddress(@bar, %bb2) ; <ptr> [#uses=1]
indirectbr ptr %1, [label %empty_block, label %bb2]

; CHECK-LABEL: bar:

empty_block: ; preds = %entry
unreachable

; CHECK-LABEL: .LBB1_1: # %empty_block

bb2: ; preds = %entry
%2 = call i32 @baz()
ret void
}

declare i32 @baz()