[llvm] 17eb6b6 - Revert "[Taildup] Don't tail-duplicate loop header with multiple successors as its latches"
Jun Ma via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 23 18:26:51 PST 2021
Author: Jun Ma
Date: 2021-11-24T10:26:37+08:00
New Revision: 17eb6b61de4b4d7a35680254a59118a0e3fa8dc9
URL: https://github.com/llvm/llvm-project/commit/17eb6b61de4b4d7a35680254a59118a0e3fa8dc9
DIFF: https://github.com/llvm/llvm-project/commit/17eb6b61de4b4d7a35680254a59118a0e3fa8dc9.diff
LOG: Revert "[Taildup] Don't tail-duplicate loop header with multiple successors as its latches"
This reverts commit 1f9fa549841a2ec55aa5a131bfaf83f0383c4713.
Added:
Modified:
llvm/lib/CodeGen/TailDuplicator.cpp
llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index 943bd18c6c8b0..54fc6ee45d00d 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -70,12 +70,6 @@ static cl::opt<unsigned> TailDupIndirectBranchSize(
"end with indirect branches."), cl::init(20),
cl::Hidden);
-static cl::opt<unsigned> TailDupJmpTableLoopSize(
- "tail-dup-jmptable-loop-size",
- cl::desc("Maximum loop latches to consider tail duplication that are "
- "successors of loop header."),
- cl::init(128), cl::Hidden);
-
static cl::opt<bool>
TailDupVerify("tail-dup-verify",
cl::desc("Verify sanity of PHI instructions during taildup"),
@@ -569,29 +563,6 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
if (TailBB.isSuccessor(&TailBB))
return false;
- // When doing tail-duplication with jumptable loops like:
- // 1 -> 2 <-> 3 |
- // \ <-> 4 |
- // \ <-> 5 |
- // \ <-> ... |
- // \---> rest |
- // quadratic number of edges and much more loops are added to CFG. This
- // may cause compile time regression when jumptable is quiet large.
- // So set the limit on jumptable cases.
- auto isLargeJumpTableLoop = [](const MachineBasicBlock &TailBB) {
- const SmallPtrSet<const MachineBasicBlock *, 8> Preds(TailBB.pred_begin(),
- TailBB.pred_end());
- // Check the basic block has large number of successors, all of them only
- // have one successor which is the basic block itself.
- return llvm::count_if(
- TailBB.successors(), [&](const MachineBasicBlock *SuccBB) {
- return Preds.count(SuccBB) && SuccBB->succ_size() == 1;
- }) > TailDupJmpTableLoopSize;
- };
-
- if (isLargeJumpTableLoop(TailBB))
- return false;
-
// Set the limit on the cost to duplicate. When optimizing for size,
// duplicate only one, because one branch instruction can be eliminated to
// compensate for the duplication.
diff --git a/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll b/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
index 25da377ec487b..2032c7244331c 100644
--- a/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
+++ b/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
@@ -1,48 +1,76 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -tail-dup-jmptable-loop-size=5 -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
define i8* @large_loop_switch(i8* %p) {
; CHECK-LABEL: large_loop_switch:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: pushq %rbx
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: .cfi_offset %rbx, -16
-; CHECK-NEXT: movq %rdi, %rsi
+; CHECK-NEXT: movq %rdi, %rax
; CHECK-NEXT: movl $6, %ebx
-; CHECK-NEXT: movl %ebx, %eax
-; CHECK-NEXT: jmpq *.LJTI0_0(,%rax,8)
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .LBB0_1: # %for.cond.cleanup
+; CHECK-NEXT: movl $530, %edi # imm = 0x212
+; CHECK-NEXT: movq %rax, %rsi
+; CHECK-NEXT: popq %rbx
+; CHECK-NEXT: .cfi_def_cfa_offset 8
+; CHECK-NEXT: jmp ccc at PLT # TAILCALL
+; CHECK-NEXT: .p2align 4, 0x90
; CHECK-NEXT: .LBB0_2: # %sw.bb1
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: movl $531, %edi # imm = 0x213
-; CHECK-NEXT: .LBB0_3: # %for.body
-; CHECK-NEXT: callq ccc at PLT
-; CHECK-NEXT: .LBB0_4: # %for.body
; CHECK-NEXT: movq %rax, %rsi
+; CHECK-NEXT: callq ccc at PLT
; CHECK-NEXT: decl %ebx
-; CHECK-NEXT: movl %ebx, %eax
-; CHECK-NEXT: jmpq *.LJTI0_0(,%rax,8)
-; CHECK-NEXT: .LBB0_5: # %sw.bb3
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_3: # %sw.bb3
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl $532, %edi # imm = 0x214
+; CHECK-NEXT: movq %rax, %rsi
; CHECK-NEXT: callq bbb at PLT
-; CHECK-NEXT: jmp .LBB0_4
-; CHECK-NEXT: .LBB0_7: # %sw.bb5
+; CHECK-NEXT: decl %ebx
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_4: # %sw.bb5
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl $533, %edi # imm = 0x215
+; CHECK-NEXT: movq %rax, %rsi
; CHECK-NEXT: callq bbb at PLT
-; CHECK-NEXT: jmp .LBB0_4
-; CHECK-NEXT: .LBB0_8: # %sw.bb7
+; CHECK-NEXT: decl %ebx
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_5: # %sw.bb7
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl $535, %edi # imm = 0x217
+; CHECK-NEXT: movq %rax, %rsi
; CHECK-NEXT: callq bbb at PLT
-; CHECK-NEXT: jmp .LBB0_4
-; CHECK-NEXT: .LBB0_9: # %sw.bb9
+; CHECK-NEXT: decl %ebx
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_6: # %sw.bb9
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl $536, %edi # imm = 0x218
-; CHECK-NEXT: jmp .LBB0_3
-; CHECK-NEXT: .LBB0_10: # %sw.bb11
+; CHECK-NEXT: movq %rax, %rsi
+; CHECK-NEXT: callq ccc at PLT
+; CHECK-NEXT: decl %ebx
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_7: # %sw.bb11
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl $658, %edi # imm = 0x292
+; CHECK-NEXT: movq %rax, %rsi
; CHECK-NEXT: callq bbb at PLT
-; CHECK-NEXT: jmp .LBB0_4
-; CHECK-NEXT: .LBB0_11: # %for.cond.cleanup
-; CHECK-NEXT: movl $530, %edi # imm = 0x212
-; CHECK-NEXT: popq %rbx
-; CHECK-NEXT: .cfi_def_cfa_offset 8
-; CHECK-NEXT: jmp ccc at PLT # TAILCALL
+; CHECK-NEXT: decl %ebx
+; CHECK-NEXT: movl %ebx, %ecx
+; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
entry:
br label %for.body
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