[llvm] r294949 - [Thumb-1] TBB generation: spot redefinitions of index register
James Molloy via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 13 06:07:39 PST 2017
Author: jamesm
Date: Mon Feb 13 08:07:39 2017
New Revision: 294949
URL: http://llvm.org/viewvc/llvm-project?rev=294949&view=rev
Log:
[Thumb-1] TBB generation: spot redefinitions of index register
We match a sequence of 3-4 instructions into a tTBB pseudo. One of our checks is that
a particular register in that sequence is killed (so it can be clobbered by the pseudo).
We weren't noticing if an errant MOV or other instruction had infiltrated the
sequence we were walking. If it had, and it defined the register we've already
identified as killed, it makes it live across the tBR_JT and thus unclobberable.
Notice this case and bail out.
Added:
llvm/trunk/test/CodeGen/Thumb/tbb-reuse.mir
Modified:
llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp
Modified: llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp?rev=294949&r1=294948&r2=294949&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp Mon Feb 13 08:07:39 2017
@@ -2009,6 +2009,16 @@ static bool jumpTableFollowsTB(MachineIn
&*MBB->begin() == CPEMI;
}
+static bool registerDefinedBetween(unsigned Reg,
+ MachineBasicBlock::iterator From,
+ MachineBasicBlock::iterator To,
+ const TargetRegisterInfo *TRI) {
+ for (auto I = From; I != To; ++I)
+ if (I->modifiesRegister(Reg, TRI))
+ return true;
+ return false;
+}
+
/// optimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller
/// jumptables when it's possible.
bool ARMConstantIslands::optimizeThumb2JumpTables() {
@@ -2095,6 +2105,7 @@ bool ARMConstantIslands::optimizeThumb2J
continue;
// If we're in PIC mode, there should be another ADD following.
+ auto *TRI = STI->getRegisterInfo();
if (isPositionIndependentOrROPI) {
MachineInstr *Add = Load->getNextNode();
if (Add->getOpcode() != ARM::tADDrr ||
@@ -2104,12 +2115,17 @@ bool ARMConstantIslands::optimizeThumb2J
continue;
if (Add->getOperand(0).getReg() != MI->getOperand(0).getReg())
continue;
-
+ if (registerDefinedBetween(IdxReg, Add->getNextNode(), MI, TRI))
+ // IdxReg gets redefined in the middle of the sequence.
+ continue;
Add->eraseFromParent();
DeadSize += 2;
} else {
if (Load->getOperand(0).getReg() != MI->getOperand(0).getReg())
continue;
+ if (registerDefinedBetween(IdxReg, Load->getNextNode(), MI, TRI))
+ // IdxReg gets redefined in the middle of the sequence.
+ continue;
}
// Now safe to delete the load and lsl. The LEA will be removed later.
Added: llvm/trunk/test/CodeGen/Thumb/tbb-reuse.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Thumb/tbb-reuse.mir?rev=294949&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Thumb/tbb-reuse.mir (added)
+++ llvm/trunk/test/CodeGen/Thumb/tbb-reuse.mir Mon Feb 13 08:07:39 2017
@@ -0,0 +1,151 @@
+# RUN: llc -run-pass arm-cp-islands %s -o - | FileCheck %s
+
+--- |
+ ; ModuleID = '<stdin>'
+ source_filename = "<stdin>"
+ target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+ target triple = "thumbv6m--none-eabi"
+
+ declare void @exit0()
+
+ declare void @exit1(i32)
+
+ declare void @exit2()
+
+ declare void @exit3()
+
+ declare void @exit4()
+
+ define void @jump_table(i32 %val, i32 %arg2, i32 %arg3, i32 %arg4) {
+ entry:
+ switch i32 %val, label %default [
+ i32 1, label %lab1
+ i32 2, label %lab2
+ i32 3, label %lab3
+ i32 4, label %lab4
+ ]
+
+ default: ; preds = %entry
+ tail call void @exit0()
+ ret void
+
+ lab1: ; preds = %entry
+ %b = sub i32 %val, 1
+ %a = shl i32 %b, 2
+ tail call void @exit1(i32 %a)
+ ret void
+
+ lab2: ; preds = %entry
+ tail call void @exit2()
+ ret void
+
+ lab3: ; preds = %entry
+ tail call void @exit3()
+ ret void
+
+ lab4: ; preds = %entry
+ tail call void @exit4()
+ ret void
+ }
+
+ ; Function Attrs: nounwind
+ declare void @llvm.stackprotector(i8*, i8**) #0
+
+ attributes #0 = { nounwind }
+
+...
+---
+name: jump_table
+alignment: 1
+exposesReturnsTwice: false
+legalized: false
+regBankSelected: false
+selected: false
+tracksRegLiveness: true
+liveins:
+ - { reg: '%r0' }
+calleeSavedRegisters: [ '%lr', '%d8', '%d9', '%d10', '%d11', '%d12', '%d13',
+ '%d14', '%d15', '%q4', '%q5', '%q6', '%q7', '%r4',
+ '%r5', '%r6', '%r7', '%r8', '%r9', '%r10', '%r11',
+ '%s16', '%s17', '%s18', '%s19', '%s20', '%s21',
+ '%s22', '%s23', '%s24', '%s25', '%s26', '%s27',
+ '%s28', '%s29', '%s30', '%s31', '%d8_d10', '%d9_d11',
+ '%d10_d12', '%d11_d13', '%d12_d14', '%d13_d15',
+ '%q4_q5', '%q5_q6', '%q6_q7', '%q4_q5_q6_q7', '%r4_r5',
+ '%r6_r7', '%r8_r9', '%r10_r11', '%d8_d9_d10', '%d9_d10_d11',
+ '%d10_d11_d12', '%d11_d12_d13', '%d12_d13_d14',
+ '%d13_d14_d15', '%d8_d10_d12', '%d9_d11_d13', '%d10_d12_d14',
+ '%d11_d13_d15', '%d8_d10_d12_d14', '%d9_d11_d13_d15',
+ '%d9_d10', '%d11_d12', '%d13_d14', '%d9_d10_d11_d12',
+ '%d11_d12_d13_d14' ]
+frameInfo:
+ isFrameAddressTaken: false
+ isReturnAddressTaken: false
+ hasStackMap: false
+ hasPatchPoint: false
+ stackSize: 8
+ offsetAdjustment: 0
+ maxAlignment: 4
+ adjustsStack: true
+ hasCalls: true
+ maxCallFrameSize: 0
+ hasOpaqueSPAdjustment: false
+ hasVAStart: false
+ hasMustTailInVarArgFunc: false
+stack:
+ - { id: 0, type: spill-slot, offset: -4, size: 4, alignment: 4, callee-saved-register: '%lr' }
+ - { id: 1, type: spill-slot, offset: -8, size: 4, alignment: 4, callee-saved-register: '%r7' }
+jumpTable:
+ kind: inline
+ entries:
+ - id: 0
+ blocks: [ '%bb.3.lab1', '%bb.4.lab2', '%bb.5.lab3', '%bb.6.lab4' ]
+# r1 is redefined in the middle of the recognizable jump sequence - it shouldn't be clobbered!
+# CHECK-NOT: tTBB_JT
+
+body: |
+ bb.0.entry:
+ successors: %bb.2.default(0x19999998), %bb.1.entry(0x66666668)
+ liveins: %r0, %r7, %lr
+
+ frame-setup tPUSH 14, _, killed %r7, killed %lr, implicit-def %sp, implicit %sp
+ frame-setup CFI_INSTRUCTION def_cfa_offset 8
+ frame-setup CFI_INSTRUCTION offset %lr, -4
+ frame-setup CFI_INSTRUCTION offset %r7, -8
+ %r1, dead %cpsr = tSUBi3 %r0, 1, 14, _
+ tCMPi8 %r1, 3, 14, _, implicit-def %cpsr
+ tBcc %bb.2.default, 8, killed %cpsr
+
+ bb.1.entry:
+ successors: %bb.3.lab1(0x20000000), %bb.4.lab2(0x20000000), %bb.5.lab3(0x20000000), %bb.6.lab4(0x20000000)
+ liveins: %r0, %r1
+
+ %r1, dead %cpsr = tLSLri killed %r1, 2, 14, _
+ %r2 = tLEApcrelJT %jump-table.0, 14, _
+ %r2 = tLDRr killed %r1, killed %r2, 14, _ :: (load 4 from jump-table)
+ %r1, dead %cpsr = tLSLri %r2, 2, 14, _
+ tBR_JTr killed %r2, %jump-table.0
+
+ bb.2.default:
+ tBL 14, _, @exit0, csr_aapcs, implicit-def dead %lr, implicit %sp, implicit-def %sp
+ tPOP_RET 14, _, def %r7, def %pc, implicit-def %sp, implicit %sp
+
+ bb.3.lab1:
+ liveins: %r0,%r1
+
+ tBL 14, _, @exit1, csr_aapcs, implicit-def dead %lr, implicit %sp, implicit %r0, implicit-def %sp
+ tPOP_RET 14, _, def %r7, def %pc, implicit-def %sp, implicit %sp
+
+ bb.4.lab2:
+ tBL 14, _, @exit2, csr_aapcs, implicit-def dead %lr, implicit %sp, implicit-def %sp
+ tPOP_RET 14, _, def %r7, def %pc, implicit-def %sp, implicit %sp
+
+ bb.5.lab3:
+ tBL 14, _, @exit3, csr_aapcs, implicit-def dead %lr, implicit %sp, implicit-def %sp
+ tPOP_RET 14, _, def %r7, def %pc, implicit-def %sp, implicit %sp
+
+ bb.6.lab4:
+ tBL 14, _, @exit4, csr_aapcs, implicit-def dead %lr, implicit %sp, implicit-def %sp
+ tPOP_RET 14, _, def %r7, def %pc, implicit-def %sp, implicit %sp
+
+...
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