diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp --- a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp +++ b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp @@ -3508,8 +3508,17 @@ MachineInstr *CondDef = MRI.getVRegDef(I.getOperand(1).getReg()); while (CondDef) { // We can only fold if all of the defs have one use. - if (!MRI.hasOneUse(CondDef->getOperand(0).getReg())) - return false; + Register CondDefReg = CondDef->getOperand(0).getReg(); + if (!MRI.hasOneUse(CondDefReg)) { + // Unless it's another select. + for (auto UI = MRI.use_instr_begin(CondDefReg), UE = MRI.use_instr_end(); + UI != UE; ++UI) { + if (CondDef == &*UI) + continue; + if (UI->getOpcode() != TargetOpcode::G_SELECT) + return false; + } + } // We can skip over G_TRUNC since the condition is 1-bit. // Truncating/extending can have no impact on the value. diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/fold-fp-select.mir b/llvm/test/CodeGen/AArch64/GlobalISel/fold-fp-select.mir --- a/llvm/test/CodeGen/AArch64/GlobalISel/fold-fp-select.mir +++ b/llvm/test/CodeGen/AArch64/GlobalISel/fold-fp-select.mir @@ -4,7 +4,7 @@ # Verify the following: # # - We can fold compares into selects. -# - This only happens when the result of the compare is only used by the select. +# - This only happens when the result of the compare is only used by selects. # # Also verify that, for now: # @@ -49,6 +49,41 @@ ... --- +name: fcmp_more_than_one_select +alignment: 4 +legalized: true +regBankSelected: true +tracksRegLiveness: true +body: | + bb.0: + liveins: $s0, $s1, $w1 + + ; CHECK-LABEL: name: fcmp_more_than_one_select + ; CHECK: liveins: $s0, $s1, $w1 + ; CHECK: [[COPY:%[0-9]+]]:fpr32 = COPY $s0 + ; CHECK: [[COPY1:%[0-9]+]]:fpr32 = COPY $s1 + ; CHECK: [[FMOVS0_:%[0-9]+]]:fpr32 = FMOVS0 + ; CHECK: FCMPSri [[COPY]], implicit-def $nzcv + ; CHECK: [[FCSELSrrr:%[0-9]+]]:fpr32 = FCSELSrrr [[FMOVS0_]], [[COPY1]], 0, implicit $nzcv + ; CHECK: FCMPSri [[COPY]], implicit-def $nzcv + ; CHECK: [[FCSELSrrr1:%[0-9]+]]:fpr32 = FCSELSrrr [[COPY1]], [[FMOVS0_]], 0, implicit $nzcv + ; CHECK: $s0 = COPY [[FCSELSrrr]] + ; CHECK: $s1 = COPY [[FCSELSrrr1]] + ; CHECK: RET_ReallyLR implicit $s0 + %0:fpr(s32) = COPY $s0 + %1:fpr(s32) = COPY $s1 + %2:fpr(s32) = G_FCONSTANT float 0.000000e+00 + %5:gpr(s32) = G_FCMP floatpred(oeq), %0(s32), %2 + %3:gpr(s1) = G_TRUNC %5(s32) + %6:fpr(s1) = COPY %3(s1) + %4:fpr(s32) = G_SELECT %6(s1), %2, %1 + %7:fpr(s32) = G_SELECT %6(s1), %1, %2 + $s0 = COPY %4(s32) + $s1 = COPY %7(s32) + RET_ReallyLR implicit $s0 + +... +--- name: using_icmp alignment: 4 legalized: true