diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp index 3b3e7a418feb5..c1e9a20328527 100644 --- a/llvm/lib/CodeGen/BranchFolding.cpp +++ b/llvm/lib/CodeGen/BranchFolding.cpp @@ -2083,22 +2083,54 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { if (TBB == FBB) { MBB->splice(Loc, TBB, TBB->begin(), TIB); } else { + // Merge the debug locations, and hoist and kill the debug instructions from + // both branches. FIXME: We could probably try harder to preserve some debug + // instructions (but at least this isn't producing wrong locations). + MachineInstrBuilder MIRBuilder(*MBB->getParent(), Loc); + auto HoistAndKillDbgInstr = [MBB, Loc](MachineBasicBlock::iterator DI) { + assert(DI->isDebugInstr() && "Expected a debug instruction"); + if (DI->isDebugRef()) { + const TargetInstrInfo *TII = + MBB->getParent()->getSubtarget().getInstrInfo(); + const MCInstrDesc &DBGV = TII->get(TargetOpcode::DBG_VALUE); + DI = BuildMI(*MBB->getParent(), DI->getDebugLoc(), DBGV, false, 0, + DI->getDebugVariable(), DI->getDebugExpression()); + MBB->insert(Loc, &*DI); + return; + } + + DI->setDebugValueUndef(); + DI->moveBefore(&*Loc); + }; + // TIB and FIB point to the end of the regions to hoist/merge in TBB and // FBB. MachineBasicBlock::iterator FE = FIB; MachineBasicBlock::iterator FI = FBB->begin(); for (MachineBasicBlock::iterator TI : make_early_inc_range(make_range(TBB->begin(), TIB))) { - // Move debug instructions and pseudo probes without modifying them. - // FIXME: This is the wrong thing to do for debug locations, which - // should at least be killed (and hoisted from BOTH blocks). - if (TI->isDebugOrPseudoInstr()) { - TI->moveBefore(&*Loc); + // Hoist and kill debug instructions from FBB. After this loop FI points + // to the next non-debug instruction to hoist (checked in assert after the + // TBB debug instruction handling code). + while (FI->isDebugInstr()) { + assert(FI != FE && "Unexpected end of FBB range"); + MachineBasicBlock::iterator FINext = std::next(FI); + HoistAndKillDbgInstr(FI); + FI = FINext; + } + + // Kill debug instructions before moving. + if (TI->isDebugInstr()) { + HoistAndKillDbgInstr(TI); continue; } - // Get the next non-meta instruction in FBB. + // If FI is a debug instruction, skip forward to the next non-debug + // instruction. FI = skipDebugInstructionsForward(FI, FE, false); + // Pseudo probes are excluded from the range when identifying foldable + // instructions, so we don't expect to see one now. + assert(!TI->isPseudoProbe() && "Unexpected pseudo probe in range"); // NOTE: The loop above checks CheckKillDead but we can't do that here as // it modifies some kill markers after the check. assert(TI->isIdenticalTo(*FI, MachineInstr::CheckDefs) && @@ -2111,6 +2143,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { ++FI; } } + FBB->erase(FBB->begin(), FIB); if (UpdateLiveIns) diff --git a/llvm/test/DebugInfo/X86/branch-folder-dbg.mir b/llvm/test/DebugInfo/X86/branch-folder-dbg.mir index 5c38fd2a43829..831b263fdccd4 100644 --- a/llvm/test/DebugInfo/X86/branch-folder-dbg.mir +++ b/llvm/test/DebugInfo/X86/branch-folder-dbg.mir @@ -1,16 +1,21 @@ # RUN: llc %s --start-before=branch-folder --stop-after=branch-folder -o - | FileCheck %s ## Check that common instructions hoisted from `if.then` and `if.else` into -## common pred `entry` get merged debug locations. - -## FIXME: The debug instructions handling here is wrong. +## common pred `entry` get merged debug locations. The debug instructions from +## both branches should get hoisted and killed. +## +## The MIR debug instructions have been modified by hand in order to check they +## can be killed. # CHECK: bb.0 # CHECK: CALL64pcrel32 @f, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, implicit-def $rax -## --- Start splice from bb.2.if.else --- -# CHECK-NEXT: DBG_VALUE 2, $noreg, ![[#]], !DIExpression(), debug-location ![[#]] -# CHECK-NEXT: $edi = MOV32r0 implicit-def dead $eflags, debug-location !DILocation(line: 0, scope: ![[#]]) -## --- End splice -------------- +## --- Start splice from bb.2.if.else (and debug instructions from bb.1.if.then) --- +# CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[#]], !DIExpression(), debug-location ![[#]] +# CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[#]], !DIExpression(), debug-location ![[#]] +# CHECK-NEXT: $edi = MOV32r0 implicit-def dead $eflags, debug-instr-number 2, debug-location !DILocation(line: 0, scope: ![[#]]) +# CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_arg, 0), debug-location ![[#]] +# CHECK-NEXT: DBG_VALUE $noreg, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_arg, 0), debug-location ![[#]] +## --- End splice ------------------------------------------------------------------ # CHECK-NEXT: TEST64rr killed renamable $rax, renamable $rax, implicit-def $eflags # CHECK-NEXT: JCC_1 %bb.2, 9, implicit killed $eflags # CHECK: bb.1 @@ -73,6 +78,8 @@ ... --- name: g +tracksRegLiveness: true +isSSA: false body: | bb.0 (%ir-block.0): successors: %bb.1(0x40000000), %bb.2(0x40000000) @@ -86,22 +93,21 @@ body: | bb.1.if.then: successors: %bb.3(0x80000000) - - DBG_VALUE 0, $noreg, !11, !DIExpression(), debug-location !13 - $edi = MOV32r0 implicit-def dead $eflags, debug-location !14 + DBG_VALUE $esi, $noreg, !11, !DIExpression(), debug-location !13 + $edi = MOV32r0 implicit-def dead $eflags, debug-instr-number 1, debug-location !14 + DBG_INSTR_REF !11, !DIExpression(DW_OP_LLVM_arg, 0), dbg-instr-ref(1, 0), debug-location !13 $esi = MOV32r0 implicit-def dead $eflags, debug-location !14 CALL64pcrel32 target-flags(x86-plt) @_Z3fooii, csr_64, implicit $rsp, implicit $ssp, implicit killed $edi, implicit killed $esi, implicit-def $rsp, implicit-def $ssp, debug-location !14 - DBG_VALUE 1, $noreg, !11, !DIExpression(), debug-location !13 JMP_1 %bb.3, debug-location !15 bb.2.if.else: successors: %bb.3(0x80000000) - DBG_VALUE 2, $noreg, !11, !DIExpression(), debug-location !13 - $edi = MOV32r0 implicit-def dead $eflags, debug-location !16 + DBG_VALUE $esp, $noreg, !11, !DIExpression(), debug-location !13 + $edi = MOV32r0 implicit-def dead $eflags, debug-instr-number 2, debug-location !16 + DBG_INSTR_REF !11, !DIExpression(DW_OP_LLVM_arg, 0), dbg-instr-ref(2, 0), debug-location !13 $esi = MOV32ri 1, debug-location !16 CALL64pcrel32 target-flags(x86-plt) @_Z3barii, csr_64, implicit $rsp, implicit $ssp, implicit killed $edi, implicit killed $esi, implicit-def $rsp, implicit-def $ssp, debug-location !16 - DBG_VALUE 3, $noreg, !11, !DIExpression(), debug-location !13 bb.3.if.end: $eax = MOV32ri 2