Skip to content

[PHIElimination] Reuse existing COPY in predecessor basic block #131837

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 4 commits into
base: main
Choose a base branch
from
Open

[PHIElimination] Reuse existing COPY in predecessor basic block #131837

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
034fe2c
[PHIElimination] Reuse existing COPY in predecessor basic block
guy-david Mar 18, 2025
8ae41e9
auto-generate updated tests
guy-david Mar 18, 2025
1a02322
Manually fixed tests
guy-david Mar 18, 2025
e549696
xfail complex test
guy-david Mar 18, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 9 additions & 0 deletions llvm/lib/CodeGen/PHIElimination.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -582,6 +582,15 @@ void PHIEliminationImpl::LowerPHINode(MachineBasicBlock &MBB,
continue;
}

// Reuse an existing copy in the block if possible.
if (MachineInstr *DefMI = MRI->getUniqueVRegDef(SrcReg)) {
if (DefMI->isCopy() && DefMI->getParent() == &opBlock &&
MRI->use_empty(SrcReg)) {
DefMI->getOperand(0).setReg(IncomingReg);
continue;
}
}

// Find a safe location to insert the copy, this may be the first terminator
// in the block (or end()).
MachineBasicBlock::iterator InsertPos =
Expand Down
16 changes: 8 additions & 8 deletions llvm/test/CodeGen/AArch64/Atomics/aarch64_be-atomic-store-outline_atomics.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -118,8 +118,8 @@ define dso_local void @store_atomic_i64_aligned_seq_cst(i64 %value, ptr %ptr) {
define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_unordered:
; -O0: bl __aarch64_cas16_relax
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
; -O0: subs x9, x0, x9
; -O0: ccmp x1, x8, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_unordered:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -131,8 +131,8 @@ define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr
define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_monotonic:
; -O0: bl __aarch64_cas16_relax
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
; -O0: subs x9, x0, x9
; -O0: ccmp x1, x8, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_monotonic:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -144,8 +144,8 @@ define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr
define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_release:
; -O0: bl __aarch64_cas16_rel
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
; -O0: subs x9, x0, x9
; -O0: ccmp x1, x8, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_release:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -157,8 +157,8 @@ define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr)
define dso_local void @store_atomic_i128_aligned_seq_cst(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_seq_cst:
; -O0: bl __aarch64_cas16_acq_rel
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
; -O0: subs x9, x0, x9
; -O0: ccmp x1, x8, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_seq_cst:
; -O1: ldaxp xzr, x8, [x2]
Expand Down
48 changes: 24 additions & 24 deletions llvm/test/CodeGen/AArch64/Atomics/aarch64_be-atomic-store-rcpc.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -117,13 +117,13 @@ define dso_local void @store_atomic_i64_aligned_seq_cst(i64 %value, ptr %ptr) {

define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_unordered:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stxp w8, x14, x15, [x9]
; -O0: stxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stxp w12, x14, x15, [x13]
; -O0: stxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_unordered:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -134,13 +134,13 @@ define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr

define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_monotonic:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stxp w8, x14, x15, [x9]
; -O0: stxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stxp w12, x14, x15, [x13]
; -O0: stxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_monotonic:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -151,13 +151,13 @@ define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr

define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_release:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stlxp w8, x14, x15, [x9]
; -O0: stlxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stlxp w12, x14, x15, [x13]
; -O0: stlxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_release:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -168,13 +168,13 @@ define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr)

define dso_local void @store_atomic_i128_aligned_seq_cst(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_seq_cst:
; -O0: ldaxp x10, x12, [x9]
; -O0: ldaxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stlxp w8, x14, x15, [x9]
; -O0: stlxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stlxp w12, x14, x15, [x13]
; -O0: stlxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_seq_cst:
; -O1: ldaxp xzr, x8, [x2]
Expand Down
48 changes: 24 additions & 24 deletions llvm/test/CodeGen/AArch64/Atomics/aarch64_be-atomic-store-v8a.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -117,13 +117,13 @@ define dso_local void @store_atomic_i64_aligned_seq_cst(i64 %value, ptr %ptr) {

define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_unordered:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stxp w8, x14, x15, [x9]
; -O0: stxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stxp w12, x14, x15, [x13]
; -O0: stxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_unordered:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -134,13 +134,13 @@ define dso_local void @store_atomic_i128_aligned_unordered(i128 %value, ptr %ptr

define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_monotonic:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stxp w8, x14, x15, [x9]
; -O0: stxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stxp w12, x14, x15, [x13]
; -O0: stxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_monotonic:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -151,13 +151,13 @@ define dso_local void @store_atomic_i128_aligned_monotonic(i128 %value, ptr %ptr

define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_release:
; -O0: ldxp x10, x12, [x9]
; -O0: ldxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stlxp w8, x14, x15, [x9]
; -O0: stlxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stlxp w12, x14, x15, [x13]
; -O0: stlxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_release:
; -O1: ldxp xzr, x8, [x2]
Expand All @@ -168,13 +168,13 @@ define dso_local void @store_atomic_i128_aligned_release(i128 %value, ptr %ptr)

define dso_local void @store_atomic_i128_aligned_seq_cst(i128 %value, ptr %ptr) {
; -O0-LABEL: store_atomic_i128_aligned_seq_cst:
; -O0: ldaxp x10, x12, [x9]
; -O0: ldaxp x8, x10, [x13]
; -O0: cmp x8, x9
; -O0: cmp x10, x11
; -O0: cmp x12, x13
; -O0: stlxp w8, x14, x15, [x9]
; -O0: stlxp w8, x10, x12, [x9]
; -O0: subs x12, x12, x13
; -O0: ccmp x10, x11, #0, eq
; -O0: stlxp w12, x14, x15, [x13]
; -O0: stlxp w12, x8, x10, [x13]
; -O0: subs x10, x10, x11
; -O0: ccmp x8, x9, #0, eq
;
; -O1-LABEL: store_atomic_i128_aligned_seq_cst:
; -O1: ldaxp xzr, x8, [x2]
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/CodeGen/AArch64/PHIElimination-debugloc.mir
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ body: |
bb.1:
%x:gpr32 = COPY $wzr
; Test that the debug location is not copied into bb1!
; CHECK: %3:gpr32 = COPY killed %x{{$}}
; CHECK: %3:gpr32 = COPY $wzr
; CHECK-LABEL: bb.2:
bb.2:
%y:gpr32 = PHI %x:gpr32, %bb.1, undef %undef:gpr32, %bb.0, debug-location !14
Expand Down
68 changes: 68 additions & 0 deletions llvm/test/CodeGen/AArch64/PHIElimination-reuse-copy.mir
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,68 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
# RUN: llc -run-pass=phi-node-elimination -mtriple=aarch64-linux-gnu -o - %s | FileCheck %s

# Verify that the original COPY in bb.1 is reappropriated as the PHI source in bb.2,
# instead of creating a new COPY with the same source register.

---
name: copy_virtual_reg
tracksRegLiveness: true
body: |
; CHECK-LABEL: name: copy_virtual_reg
; CHECK: bb.0:
; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
; CHECK-NEXT: liveins: $nzcv, $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: %a:gpr32 = COPY $w0
; CHECK-NEXT: [[DEF:%[0-9]+]]:gpr32 = IMPLICIT_DEF
; CHECK-NEXT: Bcc 8, %bb.2, implicit $nzcv
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.1:
; CHECK-NEXT: successors: %bb.2(0x80000000)
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[DEF:%[0-9]+]]:gpr32 = COPY %a
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.2:
; CHECK-NEXT: %c:gpr32 = COPY [[DEF]]
; CHECK-NEXT: %d:gpr32 = COPY %c
bb.0:
liveins: $nzcv, $w0
%a:gpr32 = COPY $w0
Bcc 8, %bb.2, implicit $nzcv
bb.1:
%b:gpr32 = COPY %a:gpr32
bb.2:
%c:gpr32 = PHI %b:gpr32, %bb.1, undef %undef:gpr32, %bb.0
%d:gpr32 = COPY %c:gpr32
...

---
name: copy_physical_reg
tracksRegLiveness: true
body: |
; CHECK-LABEL: name: copy_physical_reg
; CHECK: bb.0:
; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
; CHECK-NEXT: liveins: $nzcv, $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[DEF:%[0-9]+]]:gpr32 = IMPLICIT_DEF
; CHECK-NEXT: Bcc 8, %bb.2, implicit $nzcv
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.1:
; CHECK-NEXT: successors: %bb.2(0x80000000)
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: $x0 = IMPLICIT_DEF
; CHECK-NEXT: [[DEF:%[0-9]+]]:gpr32 = COPY $w0
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: bb.2:
; CHECK-NEXT: %b:gpr32 = COPY [[DEF]]
bb.0:
liveins: $nzcv, $w0
Bcc 8, %bb.2, implicit $nzcv
bb.1:
$x0 = IMPLICIT_DEF
%a:gpr32 = COPY $w0
bb.2:
%b:gpr32 = PHI %a:gpr32, %bb.1, undef %undef:gpr32, %bb.0
...

2 changes: 1 addition & 1 deletion llvm/test/CodeGen/AArch64/aarch64-matrix-umull-smull.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -587,8 +587,8 @@ define i16 @red_mla_dup_ext_u8_s8_s16(ptr noalias nocapture noundef readonly %A,
; CHECK-SD-NEXT: mov w10, w2
; CHECK-SD-NEXT: b.hi .LBB5_4
; CHECK-SD-NEXT: // %bb.2:
; CHECK-SD-NEXT: mov x11, xzr
; CHECK-SD-NEXT: mov w8, wzr
; CHECK-SD-NEXT: mov x11, xzr
; CHECK-SD-NEXT: b .LBB5_7
; CHECK-SD-NEXT: .LBB5_3:
; CHECK-SD-NEXT: mov w8, wzr
Expand Down
Loading
Loading