[llvm] [TailDuplicator] Only duplicate the blocks containing computed gotos (PR #114990)
via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 5 05:57:10 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-x86
Author: DianQK (DianQK)
<details>
<summary>Changes</summary>
Fixes #<!-- -->106846.
This is what I learned from GCC. I found that GCC does not duplicate the BB that has indirect jumps with the jump table. I believe GCC has provided a clear explanation here:
> Duplicate the blocks containing computed gotos. This basically unfactors computed gotos that were factored early on in the compilation process to speed up edge based data flow. We used to not unfactor them again, which can seriously pessimize code with many computed jumps in the source code, such as interpreters.
https://github.com/gcc-mirror/gcc/blob/7f67acf60c5429895d7c9e5df81796753e2913e0/gcc/bb-reorder.cc#L2757-L2761
---
Full diff: https://github.com/llvm/llvm-project/pull/114990.diff
3 Files Affected:
- (modified) llvm/include/llvm/CodeGen/MachineInstr.h (+6-2)
- (modified) llvm/lib/CodeGen/TailDuplicator.cpp (+12-10)
- (added) llvm/test/CodeGen/X86/tail-dup-computed-goto.mir (+310)
``````````diff
diff --git a/llvm/include/llvm/CodeGen/MachineInstr.h b/llvm/include/llvm/CodeGen/MachineInstr.h
index ead6bbe1d5f641..6d268628ec14b4 100644
--- a/llvm/include/llvm/CodeGen/MachineInstr.h
+++ b/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -986,8 +986,12 @@ class MachineInstr
/// Return true if this is an indirect branch, such as a
/// branch through a register.
- bool isIndirectBranch(QueryType Type = AnyInBundle) const {
- return hasProperty(MCID::IndirectBranch, Type);
+ bool isIndirectBranch(QueryType Type = AnyInBundle,
+ bool IncludeJumpTable = true) const {
+ return hasProperty(MCID::IndirectBranch, Type) &&
+ (IncludeJumpTable || !llvm::any_of(operands(), [](const auto &Op) {
+ return Op.isJTI();
+ }));
}
/// Return true if this is a branch which may fall
diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index 3f2e1511d403a0..988c58beac20f6 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -603,17 +603,19 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
TailBB.canFallThrough())
return false;
- // If the target has hardware branch prediction that can handle indirect
- // branches, duplicating them can often make them predictable when there
- // are common paths through the code. The limit needs to be high enough
- // to allow undoing the effects of tail merging and other optimizations
- // that rearrange the predecessors of the indirect branch.
-
- bool HasIndirectbr = false;
+ // Only duplicate the blocks containing computed gotos. This basically
+ // unfactors computed gotos that were factored early on in the compilation
+ // process to speed up edge based data flow. If we do not unfactor them again,
+ // it can seriously pessimize code with many computed jumps in the source
+ // code, such as interpreters.
+ bool HasComputedGoto = false;
if (!TailBB.empty())
- HasIndirectbr = TailBB.back().isIndirectBranch();
+ HasComputedGoto = TailBB.back().isIndirectBranch(
+ /*Type=*/MachineInstr::AnyInBundle,
+ // Jump tables are not considered computed gotos.
+ /*IncludeJumpTable=*/false);
- if (HasIndirectbr && PreRegAlloc)
+ if (HasComputedGoto && PreRegAlloc)
MaxDuplicateCount = TailDupIndirectBranchSize;
// Check the instructions in the block to determine whether tail-duplication
@@ -685,7 +687,7 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
}
}
- if (HasIndirectbr && PreRegAlloc)
+ if (HasComputedGoto && PreRegAlloc)
return true;
if (IsSimple)
diff --git a/llvm/test/CodeGen/X86/tail-dup-computed-goto.mir b/llvm/test/CodeGen/X86/tail-dup-computed-goto.mir
new file mode 100644
index 00000000000000..b1c699c11f4619
--- /dev/null
+++ b/llvm/test/CodeGen/X86/tail-dup-computed-goto.mir
@@ -0,0 +1,310 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=x86_64-unknown-linux-gnu -run-pass=early-tailduplication -tail-dup-size=0 %s -o - | FileCheck %s
+# Check that only the computed goto is duplicated.
+--- |
+ declare i64 @f0()
+ declare i64 @f1()
+ declare i64 @f2()
+ declare i64 @f3()
+ declare i64 @f4()
+ declare i64 @f5()
+ @computed_goto.dispatch = external global [5 x ptr]
+ define void @computed_goto() { ret void }
+ define void @jump_table() { ret void }
+...
+---
+name: computed_goto
+alignment: 16
+tracksRegLiveness: true
+noPhis: false
+isSSA: true
+noVRegs: false
+hasFakeUses: false
+debugInstrRef: true
+registers:
+ - { id: 0, class: gr64 }
+ - { id: 1, class: gr64 }
+ - { id: 2, class: gr64 }
+ - { id: 3, class: gr64 }
+ - { id: 4, class: gr64 }
+ - { id: 5, class: gr64_nosp }
+ - { id: 6, class: gr64 }
+ - { id: 7, class: gr64 }
+ - { id: 8, class: gr64 }
+ - { id: 9, class: gr64 }
+ - { id: 10, class: gr64 }
+frameInfo:
+ maxAlignment: 1
+ adjustsStack: true
+ hasCalls: true
+machineFunctionInfo:
+ amxProgModel: None
+body: |
+ ; CHECK-LABEL: name: computed_goto
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.1(0x20000000), %bb.2(0x20000000), %bb.3(0x20000000), %bb.4(0x20000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f0, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY1:%[0-9]+]]:gr64_nosp = COPY [[COPY]]
+ ; CHECK-NEXT: [[COPY2:%[0-9]+]]:gr64_nosp = COPY [[COPY1]]
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[COPY1]], @computed_goto.dispatch, $noreg
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.1(0x20000000), %bb.2(0x20000000), %bb.3(0x20000000), %bb.4(0x20000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f1, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY3:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY4:%[0-9]+]]:gr64_nosp = COPY [[COPY3]]
+ ; CHECK-NEXT: [[COPY5:%[0-9]+]]:gr64_nosp = COPY [[COPY4]]
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[COPY4]], @computed_goto.dispatch, $noreg
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: successors: %bb.1(0x20000000), %bb.2(0x20000000), %bb.3(0x20000000), %bb.4(0x20000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f2, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY6:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY7:%[0-9]+]]:gr64_nosp = COPY [[COPY6]]
+ ; CHECK-NEXT: [[COPY8:%[0-9]+]]:gr64_nosp = COPY [[COPY7]]
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[COPY7]], @computed_goto.dispatch, $noreg
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.3:
+ ; CHECK-NEXT: successors: %bb.1(0x20000000), %bb.2(0x20000000), %bb.3(0x20000000), %bb.4(0x20000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f3, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY9:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY10:%[0-9]+]]:gr64_nosp = COPY [[COPY9]]
+ ; CHECK-NEXT: [[COPY11:%[0-9]+]]:gr64_nosp = COPY [[COPY10]]
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[COPY10]], @computed_goto.dispatch, $noreg
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.4:
+ ; CHECK-NEXT: successors: %bb.1(0x20000000), %bb.2(0x20000000), %bb.3(0x20000000), %bb.4(0x20000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f4, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY12:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY13:%[0-9]+]]:gr64_nosp = COPY [[COPY12]]
+ ; CHECK-NEXT: [[COPY14:%[0-9]+]]:gr64_nosp = COPY [[COPY13]]
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[COPY13]], @computed_goto.dispatch, $noreg
+ bb.0:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f0, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %6:gr64 = COPY $rax
+ %0:gr64 = COPY %6
+ JMP_1 %bb.5
+
+ bb.1:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f1, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %10:gr64 = COPY $rax
+ %1:gr64 = COPY %10
+ JMP_1 %bb.5
+
+ bb.2:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f2, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %9:gr64 = COPY $rax
+ %2:gr64 = COPY %9
+ JMP_1 %bb.5
+
+ bb.3:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f3, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %8:gr64 = COPY $rax
+ %3:gr64 = COPY %8
+ JMP_1 %bb.5
+
+ bb.4:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f4, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %7:gr64 = COPY $rax
+ %4:gr64 = COPY %7
+
+ bb.5:
+ successors: %bb.1, %bb.2, %bb.3, %bb.4
+
+ %5:gr64_nosp = PHI %0, %bb.0, %4, %bb.4, %3, %bb.3, %2, %bb.2, %1, %bb.1
+ JMP64m $noreg, 8, %5, @computed_goto.dispatch, $noreg
+
+...
+---
+name: jump_table
+alignment: 16
+tracksRegLiveness: true
+noPhis: false
+isSSA: true
+noVRegs: false
+hasFakeUses: false
+debugInstrRef: true
+registers:
+ - { id: 0, class: gr64 }
+ - { id: 1, class: gr64 }
+ - { id: 2, class: gr64 }
+ - { id: 3, class: gr64 }
+ - { id: 4, class: gr64 }
+ - { id: 5, class: gr64 }
+ - { id: 6, class: gr64 }
+ - { id: 7, class: gr64 }
+ - { id: 8, class: gr64_nosp }
+ - { id: 9, class: gr64 }
+ - { id: 10, class: gr64 }
+ - { id: 11, class: gr64 }
+ - { id: 12, class: gr64 }
+ - { id: 13, class: gr64 }
+frameInfo:
+ maxAlignment: 1
+ adjustsStack: true
+ hasCalls: true
+machineFunctionInfo:
+ amxProgModel: None
+jumpTable:
+ kind: block-address
+ entries:
+ - id: 0
+ blocks: [ '%bb.2', '%bb.3', '%bb.4', '%bb.5', '%bb.6' ]
+body: |
+ ; CHECK-LABEL: name: jump_table
+ ; CHECK: bb.0:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f0, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY1:%[0-9]+]]:gr64 = COPY [[COPY]]
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: [[PHI:%[0-9]+]]:gr64 = PHI [[COPY1]], %bb.0, %6, %bb.7, %5, %bb.6, %4, %bb.5, %3, %bb.4, %2, %bb.3
+ ; CHECK-NEXT: [[DEC64r:%[0-9]+]]:gr64_nosp = DEC64r [[PHI]], implicit-def dead $eflags
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2:
+ ; CHECK-NEXT: successors: %bb.3(0x1999999a), %bb.4(0x1999999a), %bb.5(0x1999999a), %bb.6(0x1999999a), %bb.7(0x1999999a)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: JMP64m $noreg, 8, [[DEC64r]], %jump-table.0, $noreg :: (load (s64) from jump-table)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.3:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f1, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY2:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY3:%[0-9]+]]:gr64 = COPY [[COPY2]]
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.4:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f2, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY4:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY5:%[0-9]+]]:gr64 = COPY [[COPY4]]
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.5:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f3, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY6:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY7:%[0-9]+]]:gr64 = COPY [[COPY6]]
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.6:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f4, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY8:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY9:%[0-9]+]]:gr64 = COPY [[COPY8]]
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.7:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: CALL64pcrel32 target-flags(x86-plt) @f5, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ; CHECK-NEXT: ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ ; CHECK-NEXT: [[COPY10:%[0-9]+]]:gr64 = COPY $rax
+ ; CHECK-NEXT: [[COPY11:%[0-9]+]]:gr64 = COPY [[COPY10]]
+ ; CHECK-NEXT: JMP_1 %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.8:
+ bb.0:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f0, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %7:gr64 = COPY $rax
+ %0:gr64 = COPY %7
+
+ bb.1:
+ %1:gr64 = PHI %0, %bb.0, %6, %bb.6, %5, %bb.5, %4, %bb.4, %3, %bb.3, %2, %bb.2
+ %8:gr64_nosp = DEC64r %1, implicit-def dead $eflags
+
+ bb.8:
+ successors: %bb.2(0x1999999a), %bb.3(0x1999999a), %bb.4(0x1999999a), %bb.5(0x1999999a), %bb.6(0x1999999a)
+
+ JMP64m $noreg, 8, %8, %jump-table.0, $noreg :: (load (s64) from jump-table)
+
+ bb.2:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f1, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %13:gr64 = COPY $rax
+ %2:gr64 = COPY %13
+ JMP_1 %bb.1
+
+ bb.3:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f2, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %12:gr64 = COPY $rax
+ %3:gr64 = COPY %12
+ JMP_1 %bb.1
+
+ bb.4:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f3, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %11:gr64 = COPY $rax
+ %4:gr64 = COPY %11
+ JMP_1 %bb.1
+
+ bb.5:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f4, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %10:gr64 = COPY $rax
+ %5:gr64 = COPY %10
+ JMP_1 %bb.1
+
+ bb.6:
+ ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ CALL64pcrel32 target-flags(x86-plt) @f5, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax
+ ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp
+ %9:gr64 = COPY $rax
+ %6:gr64 = COPY %9
+ JMP_1 %bb.1
+
+ bb.7:
+
+...
``````````
</details>
https://github.com/llvm/llvm-project/pull/114990
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