[llvm] r352236 - [MBP] Don't move bottom block before header if it can't reduce taken branches
Guozhi Wei via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 25 11:45:13 PST 2019
Author: carrot
Date: Fri Jan 25 11:45:13 2019
New Revision: 352236
URL: http://llvm.org/viewvc/llvm-project?rev=352236&view=rev
Log:
[MBP] Don't move bottom block before header if it can't reduce taken branches
If bottom of block BB has only one successor OldTop, in most cases it is profitable to move it before OldTop, except the following case:
-->OldTop<-
| . |
| . |
| . |
---Pred |
| |
BB-----
Move BB before OldTop can't reduce the number of taken branches, this patch detects this case and prevent the moving.
Differential Revision: https://reviews.llvm.org/D57067
Added:
llvm/trunk/test/CodeGen/X86/code_placement_no_header_change.ll
Modified:
llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
llvm/trunk/test/CodeGen/AMDGPU/si-annotate-cf.ll
llvm/trunk/test/CodeGen/PowerPC/licm-remat.ll
llvm/trunk/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll
llvm/trunk/test/CodeGen/X86/avx-cmp.ll
llvm/trunk/test/CodeGen/X86/avx512-i1test.ll
llvm/trunk/test/DebugInfo/X86/PR37234.ll
Modified: llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp Fri Jan 25 11:45:13 2019
@@ -451,6 +451,8 @@ class MachineBlockPlacement : public Mac
void buildChain(const MachineBasicBlock *BB, BlockChain &Chain,
BlockFilterSet *BlockFilter = nullptr);
+ bool canMoveBottomBlockToTop(const MachineBasicBlock *BottomBlock,
+ const MachineBasicBlock *OldTop);
MachineBasicBlock *findBestLoopTop(
const MachineLoop &L, const BlockFilterSet &LoopBlockSet);
MachineBasicBlock *findBestLoopExit(
@@ -1756,6 +1758,39 @@ void MachineBlockPlacement::buildChain(
<< getBlockName(*Chain.begin()) << "\n");
}
+// If bottom of block BB has only one successor OldTop, in most cases it is
+// profitable to move it before OldTop, except the following case:
+//
+// -->OldTop<-
+// | . |
+// | . |
+// | . |
+// ---Pred |
+// | |
+// BB-----
+//
+// If BB is moved before OldTop, Pred needs a taken branch to BB, and it can't
+// layout the other successor below it, so it can't reduce taken branch.
+// In this case we keep its original layout.
+bool
+MachineBlockPlacement::canMoveBottomBlockToTop(
+ const MachineBasicBlock *BottomBlock,
+ const MachineBasicBlock *OldTop) {
+ if (BottomBlock->pred_size() != 1)
+ return true;
+ MachineBasicBlock *Pred = *BottomBlock->pred_begin();
+ if (Pred->succ_size() != 2)
+ return true;
+
+ MachineBasicBlock *OtherBB = *Pred->succ_begin();
+ if (OtherBB == BottomBlock)
+ OtherBB = *Pred->succ_rbegin();
+ if (OtherBB == OldTop)
+ return false;
+
+ return true;
+}
+
/// Find the best loop top block for layout.
///
/// Look for a block which is strictly better than the loop header for laying
@@ -1800,6 +1835,9 @@ MachineBlockPlacement::findBestLoopTop(c
if (Pred->succ_size() > 1)
continue;
+ if (!canMoveBottomBlockToTop(Pred, L.getHeader()))
+ continue;
+
BlockFrequency PredFreq = MBFI->getBlockFreq(Pred);
if (!BestPred || PredFreq > BestPredFreq ||
(!(PredFreq < BestPredFreq) &&
Modified: llvm/trunk/test/CodeGen/AMDGPU/si-annotate-cf.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/si-annotate-cf.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/si-annotate-cf.ll (original)
+++ llvm/trunk/test/CodeGen/AMDGPU/si-annotate-cf.ll Fri Jan 25 11:45:13 2019
@@ -96,20 +96,20 @@ declare float @llvm.fabs.f32(float) noun
; FUNC-LABEL: {{^}}loop_land_info_assert:
; SI: v_cmp_lt_i32_e64 [[CMP4:s\[[0-9:]+\]]], s{{[0-9]+}}, 4{{$}}
; SI: s_and_b64 [[CMP4M:s\[[0-9]+:[0-9]+\]]], exec, [[CMP4]]
-; SI: s_mov_b64 vcc, [[CMP4M]]
-; SI-NEXT: s_cbranch_vccnz [[CONVEX_EXIT:BB[0-9_]+]]
-; SI-NEXT: s_branch [[FOR_COND_PREHDR:BB[0-9_]+]]
+; SI: s_branch [[INFLOOP:BB[0-9]+_[0-9]+]]
+
+; SI: [[CONVEX_EXIT:BB[0-9_]+]]
+; SI: s_mov_b64 vcc,
+; SI-NEXT: s_cbranch_vccnz [[ENDPGM:BB[0-9]+_[0-9]+]]
+; SI: s_cbranch_vccnz [[INFLOOP]]
; SI: ; %if.else
; SI: buffer_store_dword
-; SI: [[INFLOOP:BB[0-9]+_[0-9]+]]:
+; SI: [[INFLOOP]]:
+; SI: s_cbranch_vccnz [[CONVEX_EXIT]]
-; SI: [[CONVEX_EXIT]]:
-; SI: s_mov_b64 vcc,
-; SI-NEXT: s_cbranch_vccnz [[ENDPGM:BB[0-9]+_[0-9]+]]
-; SI: s_branch [[INFLOOP]]
-; SI-NEXT: [[FOR_COND_PREHDR]]:
+; SI: ; %for.cond.preheader
; SI: s_cbranch_vccz [[ENDPGM]]
; SI: [[ENDPGM]]:
Modified: llvm/trunk/test/CodeGen/PowerPC/licm-remat.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/licm-remat.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/licm-remat.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/licm-remat.ll Fri Jan 25 11:45:13 2019
@@ -24,8 +24,8 @@ define linkonce_odr void @ZN6snappyDecom
; CHECK-DAG: addi 25, 3, _ZN6snappy8internalL8wordmaskE at toc@l
; CHECK-DAG: addis 5, 2, _ZN6snappy8internalL10char_tableE at toc@ha
; CHECK-DAG: addi 24, 5, _ZN6snappy8internalL10char_tableE at toc@l
-; CHECK: b .LBB0_2
-; CHECK: .LBB0_2: # %for.cond
+; CHECK: b .[[LABEL1:[A-Z0-9_]+]]
+; CHECK: .[[LABEL1]]: # %for.cond
; CHECK-NOT: addis {{[0-9]+}}, 2, _ZN6snappy8internalL8wordmaskE at toc@ha
; CHECK-NOT: addis {{[0-9]+}}, 2, _ZN6snappy8internalL10char_tableE at toc@ha
; CHECK: bctrl
Modified: llvm/trunk/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll (original)
+++ llvm/trunk/test/CodeGen/X86/2009-02-26-MachineLICMBug.ll Fri Jan 25 11:45:13 2019
@@ -20,22 +20,7 @@ define %struct.__vv* @t(%struct.Key* %de
; CHECK-NEXT: movq %rdi, %rbx
; CHECK-NEXT: orq $2097152, %r14 ## imm = 0x200000
; CHECK-NEXT: andl $15728640, %r14d ## imm = 0xF00000
-; CHECK-NEXT: jmp LBB0_1
; CHECK-NEXT: .p2align 4, 0x90
-; CHECK-NEXT: LBB0_3: ## %bb.i
-; CHECK-NEXT: ## in Loop: Header=BB0_1 Depth=1
-; CHECK-NEXT: movl 0, %eax
-; CHECK-NEXT: xorps %xmm0, %xmm0
-; CHECK-NEXT: cvtsi2ssq %rax, %xmm0
-; CHECK-NEXT: movl 4, %eax
-; CHECK-NEXT: xorps %xmm1, %xmm1
-; CHECK-NEXT: cvtsi2ssq %rax, %xmm1
-; CHECK-NEXT: movl 8, %eax
-; CHECK-NEXT: xorps %xmm2, %xmm2
-; CHECK-NEXT: cvtsi2ssq %rax, %xmm2
-; CHECK-NEXT: insertps {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[2,3]
-; CHECK-NEXT: insertps {{.*#+}} xmm0 = xmm0[0,1],xmm2[0],xmm0[3]
-; CHECK-NEXT: movaps %xmm0, 0
; CHECK-NEXT: LBB0_1: ## %bb4
; CHECK-NEXT: ## =>This Inner Loop Header: Depth=1
; CHECK-NEXT: xorl %eax, %eax
@@ -50,7 +35,21 @@ define %struct.__vv* @t(%struct.Key* %de
; CHECK-NEXT: ## in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT: cmpq $1048576, %r14 ## imm = 0x100000
; CHECK-NEXT: jne LBB0_1
-; CHECK-NEXT: jmp LBB0_3
+; CHECK-NEXT: ## %bb.3: ## %bb.i
+; CHECK-NEXT: ## in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT: movl 0, %eax
+; CHECK-NEXT: xorps %xmm0, %xmm0
+; CHECK-NEXT: cvtsi2ssq %rax, %xmm0
+; CHECK-NEXT: movl 4, %eax
+; CHECK-NEXT: xorps %xmm1, %xmm1
+; CHECK-NEXT: cvtsi2ssq %rax, %xmm1
+; CHECK-NEXT: movl 8, %eax
+; CHECK-NEXT: xorps %xmm2, %xmm2
+; CHECK-NEXT: cvtsi2ssq %rax, %xmm2
+; CHECK-NEXT: insertps {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[2,3]
+; CHECK-NEXT: insertps {{.*#+}} xmm0 = xmm0[0,1],xmm2[0],xmm0[3]
+; CHECK-NEXT: movaps %xmm0, 0
+; CHECK-NEXT: jmp LBB0_1
entry:
br label %bb4
Modified: llvm/trunk/test/CodeGen/X86/avx-cmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx-cmp.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/avx-cmp.ll (original)
+++ llvm/trunk/test/CodeGen/X86/avx-cmp.ll Fri Jan 25 11:45:13 2019
@@ -35,11 +35,7 @@ define void @render() nounwind {
; CHECK-NEXT: # %bb.1: # %for.cond5.preheader
; CHECK-NEXT: xorl %ebx, %ebx
; CHECK-NEXT: movb $1, %bpl
-; CHECK-NEXT: jmp .LBB2_2
; CHECK-NEXT: .p2align 4, 0x90
-; CHECK-NEXT: .LBB2_5: # %if.then
-; CHECK-NEXT: # in Loop: Header=BB2_2 Depth=1
-; CHECK-NEXT: callq scale
; CHECK-NEXT: .LBB2_2: # %for.cond5
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: testb %bl, %bl
@@ -52,7 +48,10 @@ define void @render() nounwind {
; CHECK-NEXT: # in Loop: Header=BB2_2 Depth=1
; CHECK-NEXT: vucomisd {{\.LCPI.*}}, %xmm0
; CHECK-NEXT: jne .LBB2_5
-; CHECK-NEXT: jp .LBB2_5
+; CHECK-NEXT: jnp .LBB2_2
+; CHECK-NEXT: .LBB2_5: # %if.then
+; CHECK-NEXT: # in Loop: Header=BB2_2 Depth=1
+; CHECK-NEXT: callq scale
; CHECK-NEXT: jmp .LBB2_2
; CHECK-NEXT: .LBB2_6: # %for.end52
; CHECK-NEXT: addq $8, %rsp
Modified: llvm/trunk/test/CodeGen/X86/avx512-i1test.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/avx512-i1test.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/avx512-i1test.ll (original)
+++ llvm/trunk/test/CodeGen/X86/avx512-i1test.ll Fri Jan 25 11:45:13 2019
@@ -15,16 +15,15 @@ define void @func() {
; CHECK-NEXT: retq
; CHECK-NEXT: .LBB0_1: # %bb56
; CHECK-NEXT: xorl %eax, %eax
-; CHECK-NEXT: jmp .LBB0_2
; CHECK-NEXT: .p2align 4, 0x90
-; CHECK-NEXT: .LBB0_3: # %bb35
-; CHECK-NEXT: # in Loop: Header=BB0_2 Depth=1
-; CHECK-NEXT: testb %al, %al
; CHECK-NEXT: .LBB0_2: # %bb33
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: testb %al, %al
; CHECK-NEXT: jne .LBB0_2
-; CHECK-NEXT: jmp .LBB0_3
+; CHECK-NEXT: # %bb.3: # %bb35
+; CHECK-NEXT: # in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT: testb %al, %al
+; CHECK-NEXT: jmp .LBB0_2
bb1:
br i1 undef, label %L_10, label %L_10
Added: llvm/trunk/test/CodeGen/X86/code_placement_no_header_change.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/code_placement_no_header_change.ll?rev=352236&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/code_placement_no_header_change.ll (added)
+++ llvm/trunk/test/CodeGen/X86/code_placement_no_header_change.ll Fri Jan 25 11:45:13 2019
@@ -0,0 +1,36 @@
+; RUN: llc -mtriple=i686-linux < %s | FileCheck %s
+
+
+define i32 @bar(i32 %count) {
+; Test checks that basic block backedge2 is not moved before header,
+; because it can't reduce taken branches.
+; Later backedge1 and backedge2 is rotated before loop header.
+; CHECK-LABEL: bar
+; CHECK: %.entry
+; CHECK: %.backedge1
+; CHECK: %.backedge2
+; CHECK: %.header
+; CHECK: %.exit
+.entry:
+ %c = shl nsw i32 %count, 2
+ br label %.header
+
+.header:
+ %val1 = call i32 @foo()
+ %cond1 = icmp sgt i32 %val1, 1
+ br i1 %cond1, label %.exit, label %.backedge1
+
+.backedge1:
+ %val2 = call i32 @foo()
+ %cond2 = icmp sgt i32 %val2, 1
+ br i1 %cond2, label %.header, label %.backedge2
+
+.backedge2:
+ %val3 = call i32 @foo()
+ br label %.header
+
+.exit:
+ ret i32 %c
+}
+
+declare i32 @foo()
Modified: llvm/trunk/test/DebugInfo/X86/PR37234.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/PR37234.ll?rev=352236&r1=352235&r2=352236&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/X86/PR37234.ll (original)
+++ llvm/trunk/test/DebugInfo/X86/PR37234.ll Fri Jan 25 11:45:13 2019
@@ -22,19 +22,18 @@
; CHECK: #DEBUG_VALUE: main:aa <- 0
; CHECK: #DEBUG_VALUE: main:aa <- $[[REG:[0-9a-z]+]]
; CHECK: jmp .LBB0_1
-; CHECK: .LBB0_3:
-; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
-; CHECK: incl %[[REG]]
-; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
+; CHECK: .LBB0_2:
+; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
+; CHECK: jne .LBB0_1
+; CHECK: # %bb.{{.*}}:
+; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
+; CHECK: incl %[[REG]]
+; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
; CHECK: .LBB0_1:
; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
-; CHECK: je .LBB0_4
+; CHECK: jne .LBB0_2
; CHECK: # %bb.{{.*}}:
; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
-; CHECK: jne .LBB0_1
-; CHECK: jmp .LBB0_3
-; CHECK: .LBB0_4:
-; CHECK: #DEBUG_VALUE: main:aa <- $[[REG]]
; CHECK: retq
source_filename = "PR37234.cpp"
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