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[MIPS] Use generic isBlockOnlyReachableByFallthrough (#80799)
FastISel may create a redundant BGTZ terminal which fallthroughes. ``` BGTZ %2:gpr32, %bb.1, implicit-def $at bb.1.bb1: ; predecessors: %bb.0 ``` The `!I->isBarrier()` check in MipsAsmPrinter::isBlockOnlyReachableByFallthrough will incorrectly not print a label, leading to a `Undefined temporary symbol ` error when we try assembling the output assembly file. See the updated `Fast-ISel/pr40325.ll` and rust-lang/rust#108835 In addition, the `SwitchInst` condition is too conservative and prints many unneeded labels (see the updated tests). Just use the generic isBlockOnlyReachableByFallthrough, updated by commit 1995b9f for SPARC, which also handles MIPS.
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‎llvm/lib/Target/Mips/MipsAsmPrinter.cpp‎

Lines changed: 0 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -471,45 +471,6 @@ void MipsAsmPrinter::emitBasicBlockEnd(const MachineBasicBlock &MBB) {
471471
TS.emitDirectiveInsn();
472472
}
473473

474-
/// isBlockOnlyReachableByFallthough - Return true if the basic block has
475-
/// exactly one predecessor and the control transfer mechanism between
476-
/// the predecessor and this block is a fall-through.
477-
bool MipsAsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock*
478-
MBB) const {
479-
// The predecessor has to be immediately before this block.
480-
const MachineBasicBlock *Pred = *MBB->pred_begin();
481-
482-
// If the predecessor is a switch statement, assume a jump table
483-
// implementation, so it is not a fall through.
484-
if (const BasicBlock *bb = Pred->getBasicBlock())
485-
if (isa<SwitchInst>(bb->getTerminator()))
486-
return false;
487-
488-
// If this is a landing pad, it isn't a fall through. If it has no preds,
489-
// then nothing falls through to it.
490-
if (MBB->isEHPad() || MBB->pred_empty())
491-
return false;
492-
493-
// If there isn't exactly one predecessor, it can't be a fall through.
494-
if (MBB->pred_size() != 1)
495-
return false;
496-
497-
// The predecessor has to be immediately before this block.
498-
if (!Pred->isLayoutSuccessor(MBB))
499-
return false;
500-
501-
// If the block is completely empty, then it definitely does fall through.
502-
if (Pred->empty())
503-
return true;
504-
505-
// Otherwise, check the last instruction.
506-
// Check if the last terminator is an unconditional branch.
507-
MachineBasicBlock::const_iterator I = Pred->end();
508-
while (I != Pred->begin() && !(--I)->isTerminator()) ;
509-
510-
return !I->isBarrier();
511-
}
512-
513474
// Print out an operand for an inline asm expression.
514475
bool MipsAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
515476
const char *ExtraCode, raw_ostream &O) {

‎llvm/lib/Target/Mips/MipsAsmPrinter.h‎

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -142,8 +142,6 @@ class LLVM_LIBRARY_VISIBILITY MipsAsmPrinter : public AsmPrinter {
142142
void emitFunctionBodyStart() override;
143143
void emitFunctionBodyEnd() override;
144144
void emitBasicBlockEnd(const MachineBasicBlock &MBB) override;
145-
bool isBlockOnlyReachableByFallthrough(
146-
const MachineBasicBlock* MBB) const override;
147145
bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
148146
const char *ExtraCode, raw_ostream &O) override;
149147
bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,

‎llvm/test/CodeGen/Mips/Fast-ISel/pr40325.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@ define void @test(i32 %x, ptr %p) nounwind {
1111
; CHECK-NEXT: andi $1, $4, 1
1212
; CHECK-NEXT: bgtz $1, $BB0_1
1313
; CHECK-NEXT: nop
14-
; CHECK-NEXT: # %bb.1: # %foo
14+
; CHECK-NEXT: $BB0_1: # %foo
1515
; CHECK-NEXT: jr $ra
1616
; CHECK-NEXT: nop
1717
%y = and i32 %x, 1

‎llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/jump_table_and_brjt.ll‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -25,7 +25,7 @@ define i32 @mod4_0_to_11(i32 %a) {
2525
; MIPS32-NEXT: sltu $1, $1, $2
2626
; MIPS32-NEXT: bnez $1, $BB0_6
2727
; MIPS32-NEXT: nop
28-
; MIPS32-NEXT: $BB0_1: # %entry
28+
; MIPS32-NEXT: # %bb.1: # %entry
2929
; MIPS32-NEXT: lw $2, 28($sp) # 4-byte Folded Reload
3030
; MIPS32-NEXT: lui $1, %hi($JTI0_0)
3131
; MIPS32-NEXT: sll $2, $2, 2
@@ -65,7 +65,7 @@ define i32 @mod4_0_to_11(i32 %a) {
6565
; MIPS32-NEXT: sltu $1, $1, $2
6666
; MIPS32-NEXT: bnez $1, $BB0_13
6767
; MIPS32-NEXT: nop
68-
; MIPS32-NEXT: $BB0_8: # %sw.epilog
68+
; MIPS32-NEXT: # %bb.8: # %sw.epilog
6969
; MIPS32-NEXT: lw $2, 0($sp) # 4-byte Folded Reload
7070
; MIPS32-NEXT: lui $1, %hi($JTI0_1)
7171
; MIPS32-NEXT: sll $2, $2, 2
@@ -125,7 +125,7 @@ define i32 @mod4_0_to_11(i32 %a) {
125125
; MIPS32_PIC-NEXT: sltu $1, $1, $2
126126
; MIPS32_PIC-NEXT: bnez $1, $BB0_6
127127
; MIPS32_PIC-NEXT: nop
128-
; MIPS32_PIC-NEXT: $BB0_1: # %entry
128+
; MIPS32_PIC-NEXT: # %bb.1: # %entry
129129
; MIPS32_PIC-NEXT: lw $2, 8($sp) # 4-byte Folded Reload
130130
; MIPS32_PIC-NEXT: lw $3, 36($sp) # 4-byte Folded Reload
131131
; MIPS32_PIC-NEXT: lw $1, %got($JTI0_0)($2)
@@ -167,7 +167,7 @@ define i32 @mod4_0_to_11(i32 %a) {
167167
; MIPS32_PIC-NEXT: sltu $1, $1, $2
168168
; MIPS32_PIC-NEXT: bnez $1, $BB0_13
169169
; MIPS32_PIC-NEXT: nop
170-
; MIPS32_PIC-NEXT: $BB0_8: # %sw.epilog
170+
; MIPS32_PIC-NEXT: # %bb.8: # %sw.epilog
171171
; MIPS32_PIC-NEXT: lw $2, 8($sp) # 4-byte Folded Reload
172172
; MIPS32_PIC-NEXT: lw $3, 4($sp) # 4-byte Folded Reload
173173
; MIPS32_PIC-NEXT: lw $1, %got($JTI0_1)($2)

‎llvm/test/CodeGen/Mips/compactbranches/unsafe-in-forbidden-slot.ll‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -18,15 +18,15 @@ sw.bb: ; preds = %entry
1818
br label %sw.epilog
1919
; CHECK: beqzc
2020
; CHECK-NEXT: nop
21-
; CHECK-NEXT: .LBB
21+
; CHECK-NEXT: # %bb.1
2222
; CHECK-NEXT: j
2323

2424
sw.bb1: ; preds = %entry, %entry
2525
store volatile i32 2, ptr @boo, align 4
2626
br label %sw.epilog
2727
; CHECK: bnezc
2828
; CHECK-NEXT: nop
29-
; CHECK-NEXT: .LBB
29+
; CHECK-NEXT: # %bb.3
3030
; CHECK-NEXT: j
3131

3232
sw.epilog: ; preds = %entry, %sw.bb1, %sw.bb

‎llvm/test/CodeGen/Mips/indirect-jump-hazard/jumptables.ll‎

Lines changed: 8 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -42,7 +42,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
4242
; MIPS32R2-NEXT: sltiu $1, $4, 7
4343
; MIPS32R2-NEXT: beqz $1, $BB0_6
4444
; MIPS32R2-NEXT: sw $4, 4($sp)
45-
; MIPS32R2-NEXT: $BB0_1: # %entry
45+
; MIPS32R2-NEXT: # %bb.1: # %entry
4646
; MIPS32R2-NEXT: sll $1, $4, 2
4747
; MIPS32R2-NEXT: lui $2, %hi($JTI0_0)
4848
; MIPS32R2-NEXT: addu $1, $1, $2
@@ -100,7 +100,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
100100
; MIPS32R6-NEXT: sltiu $1, $4, 7
101101
; MIPS32R6-NEXT: beqz $1, $BB0_6
102102
; MIPS32R6-NEXT: sw $4, 4($sp)
103-
; MIPS32R6-NEXT: $BB0_1: # %entry
103+
; MIPS32R6-NEXT: # %bb.1: # %entry
104104
; MIPS32R6-NEXT: sll $1, $4, 2
105105
; MIPS32R6-NEXT: lui $2, %hi($JTI0_0)
106106
; MIPS32R6-NEXT: addu $1, $1, $2
@@ -159,7 +159,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
159159
; MIPS64R2-NEXT: sltiu $1, $2, 7
160160
; MIPS64R2-NEXT: beqz $1, .LBB0_6
161161
; MIPS64R2-NEXT: sw $4, 4($sp)
162-
; MIPS64R2-NEXT: .LBB0_1: # %entry
162+
; MIPS64R2-NEXT: # %bb.1: # %entry
163163
; MIPS64R2-NEXT: dsll $1, $2, 3
164164
; MIPS64R2-NEXT: lui $2, %highest(.LJTI0_0)
165165
; MIPS64R2-NEXT: daddiu $2, $2, %higher(.LJTI0_0)
@@ -254,7 +254,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
254254
; MIPS64R6-NEXT: sltiu $1, $2, 7
255255
; MIPS64R6-NEXT: beqz $1, .LBB0_6
256256
; MIPS64R6-NEXT: sw $4, 4($sp)
257-
; MIPS64R6-NEXT: .LBB0_1: # %entry
257+
; MIPS64R6-NEXT: # %bb.1: # %entry
258258
; MIPS64R6-NEXT: dsll $1, $2, 3
259259
; MIPS64R6-NEXT: lui $2, %highest(.LJTI0_0)
260260
; MIPS64R6-NEXT: daddiu $2, $2, %higher(.LJTI0_0)
@@ -351,7 +351,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
351351
; PIC-MIPS32R2-NEXT: sltiu $1, $4, 7
352352
; PIC-MIPS32R2-NEXT: beqz $1, $BB0_6
353353
; PIC-MIPS32R2-NEXT: sw $4, 4($sp)
354-
; PIC-MIPS32R2-NEXT: $BB0_1: # %entry
354+
; PIC-MIPS32R2-NEXT: # %bb.1: # %entry
355355
; PIC-MIPS32R2-NEXT: sll $1, $4, 2
356356
; PIC-MIPS32R2-NEXT: lw $3, %got($JTI0_0)($2)
357357
; PIC-MIPS32R2-NEXT: addu $1, $1, $3
@@ -413,7 +413,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
413413
; PIC-MIPS32R6-NEXT: sltiu $1, $4, 7
414414
; PIC-MIPS32R6-NEXT: beqz $1, $BB0_6
415415
; PIC-MIPS32R6-NEXT: sw $4, 4($sp)
416-
; PIC-MIPS32R6-NEXT: $BB0_1: # %entry
416+
; PIC-MIPS32R6-NEXT: # %bb.1: # %entry
417417
; PIC-MIPS32R6-NEXT: sll $1, $4, 2
418418
; PIC-MIPS32R6-NEXT: lw $3, %got($JTI0_0)($2)
419419
; PIC-MIPS32R6-NEXT: addu $1, $1, $3
@@ -476,7 +476,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
476476
; PIC-MIPS64R2-NEXT: sltiu $1, $3, 7
477477
; PIC-MIPS64R2-NEXT: beqz $1, .LBB0_6
478478
; PIC-MIPS64R2-NEXT: sw $4, 4($sp)
479-
; PIC-MIPS64R2-NEXT: .LBB0_1: # %entry
479+
; PIC-MIPS64R2-NEXT: # %bb.1: # %entry
480480
; PIC-MIPS64R2-NEXT: dsll $1, $3, 3
481481
; PIC-MIPS64R2-NEXT: ld $3, %got_page(.LJTI0_0)($2)
482482
; PIC-MIPS64R2-NEXT: daddu $1, $1, $3
@@ -539,7 +539,7 @@ define ptr @_Z3fooi(i32 signext %Letter) {
539539
; PIC-MIPS64R6-NEXT: sltiu $1, $3, 7
540540
; PIC-MIPS64R6-NEXT: beqz $1, .LBB0_6
541541
; PIC-MIPS64R6-NEXT: sw $4, 4($sp)
542-
; PIC-MIPS64R6-NEXT: .LBB0_1: # %entry
542+
; PIC-MIPS64R6-NEXT: # %bb.1: # %entry
543543
; PIC-MIPS64R6-NEXT: dsll $1, $3, 3
544544
; PIC-MIPS64R6-NEXT: ld $3, %got_page(.LJTI0_0)($2)
545545
; PIC-MIPS64R6-NEXT: daddu $1, $1, $3

‎llvm/test/CodeGen/Mips/jump-table-mul.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@ define i64 @test(i64 %arg) {
1010
; CHECK-NEXT: sltiu $1, $4, 11
1111
; CHECK-NEXT: beqz $1, .LBB0_4
1212
; CHECK-NEXT: nop
13-
; CHECK-NEXT: .LBB0_1: # %entry
13+
; CHECK-NEXT: # %bb.1: # %entry
1414
; CHECK-NEXT: daddiu $1, $2, %lo(%neg(%gp_rel(test)))
1515
; CHECK-NEXT: dsll $2, $4, 3
1616
; CHECK-NEXT: ld $3, %got_page(.LJTI0_0)($1)

‎llvm/test/CodeGen/Mips/pseudo-jump-fill.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@ define i32 @test(i32 signext %x, i32 signext %c) {
1414
; CHECK-NEXT: sltiu $1, $5, 4
1515
; CHECK-NEXT: beqz $1, $BB0_6
1616
; CHECK-NEXT: addu $3, $2, $25
17-
; CHECK-NEXT: $BB0_1: # %entry
17+
; CHECK-NEXT: # %bb.1: # %entry
1818
; CHECK-NEXT: li16 $2, 0
1919
; CHECK-NEXT: sll16 $5, $5, 2
2020
; CHECK-NEXT: lw $6, %got($JTI0_0)($3)

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