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[X86] Respect blockaddress offsets when performing X86 LEA fixups (#71641)

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The X86FixupLEAs pass drops blockaddress offsets, when splitting up slow
3-ops LEAs, as can be seen in this example:

https://godbolt.org/z/bEsc3Poje

Before running the pass, the first instruction in bb.0 is a LEA with
ebp, ebx and a blockaddress.
After the transformation, the blockaddress is missing.

The reason this happens is because the 3-ops LEA is being splitup into a
2-ops LEA + an add instruction.
However, as hasLEAOffset does not take blockaddresses into
consideration, the add is not emitted and thus leading to the offset
being dropped.

Taking blockaddresses into consideration fixes this issue and results in
the add instruction being emitted.

This fixes #71667
This commit is contained in:
Maurice Heumann 2023-11-10 01:12:18 +01:00 committed by GitHub
parent a5a0248835
commit 8cbfc0b29d
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2 changed files with 32 additions and 1 deletions
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3
llvm/lib/Target/X86/X86FixupLEAs.cpp
View File

@ -341,7 +341,8 @@ static inline bool hasInefficientLEABaseReg(const MachineOperand &Base,
}
static inline bool hasLEAOffset(const MachineOperand &Offset) {
return (Offset.isImm() && Offset.getImm() != 0) || Offset.isGlobal();
return (Offset.isImm() && Offset.getImm() != 0) || Offset.isGlobal() ||
Offset.isBlockAddress();
}
static inline unsigned getADDrrFromLEA(unsigned LEAOpcode) {

30
llvm/test/CodeGen/X86/lea-fixup-blockaddress.mir Normal file
View File

@ -0,0 +1,30 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 3
# RUN: llc -mtriple=i386-unknown-linux-gnu -mattr=slow-3ops-lea -run-pass x86-fixup-LEAs -o - %s | FileCheck %s
--- |
define i32 @square(i32 %0) local_unnamed_addr {
%blub = getelementptr i8, ptr blockaddress(@square, %2), i32 %0
indirectbr ptr %blub, [label %2]
2:
ret i32 0
}
---
name: square
body: |
; CHECK-LABEL: name: square
; CHECK: bb.0:
; CHECK-NEXT: renamable $eax = LEA32r renamable $ebx, 1, renamable $ebp, 0, $noreg
; CHECK-NEXT: $eax = ADD32ri $eax, target-flags(x86-gotoff) blockaddress(@square, %ir-block.1), implicit-def $eflags
; CHECK-NEXT: JMP32r killed renamable $eax
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.1 (%ir-block.1, ir-block-address-taken %ir-block.1):
; CHECK-NEXT: RET 0
bb.0:
renamable $eax = LEA32r renamable $ebp, 1, renamable $ebx, target-flags(x86-gotoff) blockaddress(@square, %ir-block.1), $noreg
JMP32r killed renamable $eax
bb.1 (%ir-block.1, ir-block-address-taken %ir-block.1):
RET 0
...