[PowerPC] CTRLoop pseudo instructions should not be duplicated

[tingwang]

Summary

Add isNotDuplicable to CTRLoop pseudo instructions, to avoid other pass such as early-tailduplication break the loop structure by duplicating pseudo instructions.

Attached test case will be added before and removed by this fix.

[shchenz]

Attached test case will be added before and removed by this fix.

Do you mean you plan to remove the test case? I think the test case should still be kept and check that a ctr-loop is generated after this fix.

llvm/lib/Target/PowerPC/PPCInstr64Bit.td

576–578

Maybe we can add some comments for this change, like MTCTR8loop must be inside a loop-preheader, duplicating the loop-preheader block will break this assumption?

[tingwang]

(1) Add comment.
(2) Update test case.

[tingwang]

In D132738#3754410, @shchenz wrote:

Attached test case will be added before and removed by this fix.

Do you mean you plan to remove the test case? I think the test case should still be kept and check that a ctr-loop is generated after this fix.

Sure. Test case updated.

[shchenz]

Thanks for fixing. LGTM

llvm/lib/Target/PowerPC/PPCInstr64Bit.td

def MFCTR8 : XFXForm_1_ext<31, 339, 9, (outs g8rc:$rT), (ins),
                            "mfctr $rT", IIC_SprMFSPR>,
              PPC970_DGroup_First, PPC970_Unit_FXU;
 }
 let Pattern = [(PPCmtctr i64:$rS)], Defs = [CTR8] in {
 def MTCTR8 : XFXForm_7_ext<31, 467, 9, (outs), (ins g8rc:$rS),
                            "mtctr $rS", IIC_SprMTSPR>,
              PPC970_DGroup_First, PPC970_Unit_FXU;
 }
-let hasSideEffects = 1, Defs = [CTR8] in {
+// MTCTR[8|]loop must be inside a loop-preheader, duplicating
+// the loop-preheader block will break this assumption.
+let hasSideEffects = 1, isNotDuplicable = 1, Defs = [CTR8] in {
 let Pattern = [(int_set_loop_iterations i64:$rS)] in
 def MTCTR8loop : XFXForm_7_ext<31, 467, 9, (outs), (ins g8rc:$rS),
                                "mtctr $rS", IIC_SprMTSPR>,
                  PPC970_DGroup_First, PPC970_Unit_FXU;
 }
 
-let hasSideEffects = 1, hasNoSchedulingInfo = 1, Uses = [CTR8], Defs = [CTR8] in
+let hasSideEffects = 1, hasNoSchedulingInfo = 1, isNotDuplicable = 1, Uses = [CTR8], Defs = [CTR8] in
 def DecreaseCTR8loop : PPCEmitTimePseudo<(outs crbitrc:$rT), (ins i64imm:$stride),
                                         "#DecreaseCTR8loop", [(set i1:$rT, (int_loop_decrement (i64 imm:$stride)))]>;
 
 let Pattern = [(set i64:$rT, readcyclecounter)] in
 def MFTB8 : XFXForm_1_ext<31, 339, 268, (outs g8rc:$rT), (ins),
                           "mfspr $rT, 268", IIC_SprMFTB>,
             PPC970_DGroup_First, PPC970_Unit_FXU;
 // Note that encoding mftb using mfspr is now the preferred form,

llvm/lib/Target/PowerPC/PPCInstrInfo.td

def MFCTR : XFXForm_1_ext<31, 339, 9, (outs gprc:$rT), (ins),
                           "mfctr $rT", IIC_SprMFSPR>,
             PPC970_DGroup_First, PPC970_Unit_FXU;
 }
 let Defs = [CTR], Pattern = [(PPCmtctr i32:$rS)] in {
 def MTCTR : XFXForm_7_ext<31, 467, 9, (outs), (ins gprc:$rS),
                           "mtctr $rS", IIC_SprMTSPR>,
             PPC970_DGroup_First, PPC970_Unit_FXU;
 }
-let hasSideEffects = 1, isCodeGenOnly = 1, Defs = [CTR] in {
+let hasSideEffects = 1, isCodeGenOnly = 1, isNotDuplicable = 1, Defs = [CTR] in {
 let Pattern = [(int_set_loop_iterations i32:$rS)] in
 def MTCTRloop : XFXForm_7_ext<31, 467, 9, (outs), (ins gprc:$rS),
                               "mtctr $rS", IIC_SprMTSPR>,
                 PPC970_DGroup_First, PPC970_Unit_FXU;
 }
 
-let hasSideEffects = 1, hasNoSchedulingInfo = 1, Uses = [CTR], Defs = [CTR] in
+let hasSideEffects = 1, hasNoSchedulingInfo = 1, isNotDuplicable = 1, Uses = [CTR], Defs = [CTR] in
 def DecreaseCTRloop : PPCEmitTimePseudo<(outs crbitrc:$rT), (ins i32imm:$stride),
                                        "#DecreaseCTRloop", [(set i1:$rT, (int_loop_decrement (i32 imm:$stride)))]>;
 
 let hasSideEffects = 0 in {
 let Defs = [LR] in {
 def MTLR  : XFXForm_7_ext<31, 467, 8, (outs), (ins gprc:$rS),
                           "mtlr $rS", IIC_SprMTSPR>,
             PPC970_DGroup_First, PPC970_Unit_FXU;

llvm/test/CodeGen/PowerPC/ctrloop-do-not-duplicate-mi.mir

-# RUN: not --crash llc -ppc-asm-full-reg-names -mtriple=powerpc64le-unknown-linux-gnu \
+# RUN: llc -ppc-asm-full-reg-names -mtriple=powerpc64le-unknown-linux-gnu \
 # RUN:   -run-pass=early-tailduplication,ppc-ctrloops %s -o - -verify-machineinstrs 2>&1 | FileCheck %s
 
-# CHECK: Invalid ctr loop
 --- |
   target datalayout = "e-m:e-i64:64-n32:64-S128-v256:256:256-v512:512:512"
   target triple = "powerpc64le-unknown-linux-gnu"
   
   define dso_local void @test() local_unnamed_addr #0 {
   test_entry:
     %_val_domain_ = load i32, i32* undef, align 4
     %_conv765 = sext i32 %_val_domain_ to i64
--- |
   
   !llvm.ident = !{!0}
   
   !0 = !{!""}
 
 ...
 ---
 name:            test
+# CHECK: test
 alignment:       16
 exposesReturnsTwice: false
 legalized:       false
 regBankSelected: false
 selected:        false
 failedISel:      false
 tracksRegLiveness: true
 hasWinCFI:       false