[PowerPC] set min jump table entries to 64

[shchenz]

Summary

This benefits some benchmarks on PPC targets.

And also add a new PPC specific option -ppc-min-jump-table-entries to keep the ability to change the setting from the command line. (After calling setMinimumJumpTableEntries() on PPC, target independent option -min-jump-table-entries does not work.)

[efriedma]

I don't have access to any relevant PPC hardware to benchmark, but 64 seems excessively high. I mean, I can imagine it benefiting certain micro-benchmarks if it helps branch prediction in some hot code. But it's high enough that it likely also hurts other benchmarks, and maybe increases codesize.

[shchenz]

I don't have access to any relevant PPC hardware to benchmark, but 64 seems excessively high. I mean, I can imagine it benefiting certain micro-benchmarks if it helps branch prediction in some hot code. But it's high enough that it likely also hurts other benchmarks, and maybe increases codesize.

Thanks for taking a look. I agree with you that setting this value to 64 has the possibility to hurt some applications. 64 is an experiment result based on benchmarks we(IBM Power team) care about currently. This value improves some benchmarks and does not have obvious negative impact for other ones. So we decide to change the default value. codesize is a good point, we can find out a new value for code size purpose if codesize becomes a concern for us later.

[efriedma]

Okay; as long as you're keeping that in mind, patch seems fine.

[nemanjai]

The reason 64 seems to be a good value on PPC chips is hopefully a transient situation that seems to have something to do with how bad the chips can be with branch prediction for indirect branches (CTR branches). I think at least some indication should be added in code comments suggesting this be re-evaluated on future HW that will hopefully do better with this kind of branch.
The other knob we have access to wrt. jump tables (density) could probably use some tuning as well.

Other than the above (which doesn't require another review), LGTM.

llvm/lib/Target/PowerPC/PPCISelLowering.cpp

DisablePerfectShuffle("ppc-disable-perfect-shuffle",
                           cl::desc("disable vector permute decomposition"),
                           cl::init(true), cl::Hidden);
 
 cl::opt<bool> DisableAutoPairedVecSt(
     "disable-auto-paired-vec-st",
     cl::desc("disable automatically generated 32byte paired vector stores"),
     cl::init(true), cl::Hidden);
 
+static cl::opt<unsigned> PPCMinimumJumpTableEntries(
+    "ppc-min-jump-table-entries", cl::init(64), cl::Hidden,
+    cl::desc("Set minimum number of entries to use a jump table on PPC"));
+
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumSiblingCalls, "Number of sibling calls");
 STATISTIC(ShufflesHandledWithVPERM,
           "Number of shuffles lowered to a VPERM or XXPERM");
 STATISTIC(NumDynamicAllocaProbed, "Number of dynamic stack allocation probed");
 
 static bool isNByteElemShuffleMask(ShuffleVectorSDNode *, unsigned, int);
 

 
   // With 32 condition bits, we don't need to sink (and duplicate) compares
   // aggressively in CodeGenPrep.
   if (Subtarget.useCRBits()) {
     setHasMultipleConditionRegisters();
     setJumpIsExpensive();
   }
 
+  // TODO: The default entry number is set to 64. This stops most jump table
+  // generation on PPC. But it is good for current PPC HWs because the indirect
+  // branch instruction mtctr to the jump table may lead to bad branch predict.
+  // Re-evaluate this value on future HWs that can do better with mtctr.
+  setMinimumJumpTableEntries(PPCMinimumJumpTableEntries);
+
   setMinFunctionAlignment(Align(4));
 
   switch (Subtarget.getCPUDirective()) {
   default: break;
   case PPC::DIR_970:
   case PPC::DIR_A2:
   case PPC::DIR_E500:
   case PPC::DIR_E500mc:

llvm/test/CodeGen/PowerPC/absol-jump-table-enabled.ll

 ; NOTE: This test case generates a jump table on PowerPC big and little endian
 ; NOTE: then verifies that the command line option to enable absolute jump
 ; NOTE: table works correctly.
-; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables -ppc-asm-full-reg-names \
 ; RUN:      -verify-machineinstrs %s | FileCheck %s -check-prefix=CHECK-LE
-; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables -ppc-asm-full-reg-names \
 ; RUN:      -verify-machineinstrs %s | FileCheck %s -check-prefix=CHECK-BE
-; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -o - \
+; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables -ppc-asm-full-reg-names \
 ; RUN:      -verify-machineinstrs %s | FileCheck %s -check-prefix=CHECK-AIX
-; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=true --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-A-PIC-LE
-; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=false --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-R-PIC-LE
-; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=true --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-A-PIC-BE
-; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=false --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-R-PIC-BE
-; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -o - \
+; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=true --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-A-PIC-AIX
-; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -o - \
+; RUN:  llc -mtriple=powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=false --relocation-model=pic < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-R-PIC-AIX
-; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=true --relocation-model=static < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-A-STATIC-LE
-; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=false --relocation-model=static < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-R-STATIC-LE
-; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=true --relocation-model=static < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-A-STATIC-BE
-; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -o - \
+; RUN:  llc -mtriple=powerpc64-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:      -ppc-use-absolute-jumptables=false --relocation-model=static < %s | FileCheck %s \
 ; RUN:      -check-prefix=CHECK-R-STATIC-BE
 
 %struct.node = type { i8, ptr }
 
 ; Function Attrs: norecurse nounwind readonly
 define zeroext i32 @jumpTableTest(ptr readonly %list) {
 ; CHECK-LE-LABEL: jumpTableTest:

llvm/test/CodeGen/PowerPC/aix-lower-jump-table.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
 ; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mattr=-altivec -mtriple powerpc-ibm-aix-xcoff \
-; RUN: -code-model=small -stop-after=machine-cp < %s | FileCheck \
+; RUN: -ppc-min-jump-table-entries=4 -code-model=small -stop-after=machine-cp < %s | FileCheck \
 ; RUN: --check-prefix=32SMALL-MIR %s
 
 ; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mattr=-altivec -mtriple powerpc-ibm-aix-xcoff \
-; RUN: -code-model=large -stop-after=machine-cp < %s | FileCheck \
+; RUN: -ppc-min-jump-table-entries=4 -code-model=large -stop-after=machine-cp < %s | FileCheck \
 ; RUN: --check-prefix=32LARGE-MIR %s
 
 ; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mattr=-altivec -mtriple powerpc64-ibm-aix-xcoff \
-; RUN: -code-model=small -stop-after=machine-cp < %s | FileCheck \
+; RUN: -ppc-min-jump-table-entries=4 -code-model=small -stop-after=machine-cp < %s | FileCheck \
 ; RUN: --check-prefix=64SMALL-MIR %s
 
 ; RUN: llc -verify-machineinstrs -mcpu=pwr7 -mattr=-altivec -mtriple powerpc64-ibm-aix-xcoff \
-; RUN: -code-model=large -stop-after=machine-cp < %s | FileCheck \
+; RUN: -ppc-min-jump-table-entries=4 -code-model=large -stop-after=machine-cp < %s | FileCheck \
 ; RUN: --check-prefix=64LARGE-MIR %s
 
-; RUN: llc -mtriple powerpc-ibm-aix-xcoff -code-model=small < %s | FileCheck \
+; RUN: llc -mtriple powerpc-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -code-model=small < %s | FileCheck \
 ; RUN: --check-prefixes=32SMALL-ASM,SMALL-ASM %s
 
-; RUN: llc -mtriple powerpc-ibm-aix-xcoff -code-model=large < %s | FileCheck \
+; RUN: llc -mtriple powerpc-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -code-model=large < %s | FileCheck \
 ; RUN: --check-prefixes=32LARGE-ASM,LARGE-ASM %s
 
-; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -code-model=small < %s | FileCheck \
+; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -code-model=small < %s | FileCheck \
 ; RUN: --check-prefixes=64SMALL-ASM,SMALL-ASM %s
 
-; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -code-model=large < %s | FileCheck \
+; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -code-model=large < %s | FileCheck \
 ; RUN: --check-prefixes=64LARGE-ASM,LARGE-ASM %s
 
-; RUN: llc -mtriple powerpc-ibm-aix-xcoff -function-sections < %s | FileCheck \
+; RUN: llc -mtriple powerpc-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -function-sections < %s | FileCheck \
 ; RUN: --check-prefix=FUNC-ASM %s
 
-; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -function-sections < %s | FileCheck \
+; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -ppc-min-jump-table-entries=4 -function-sections < %s | FileCheck \
 ; RUN: --check-prefix=FUNC-ASM %s
 
 define i32 @jump_table(i32 %a) {
 ; 32SMALL-ASM-LABEL: jump_table:
 ; 32SMALL-ASM:       # %bb.0: # %entry
 ; 32SMALL-ASM-NEXT:    addi 3, 3, -1
 ; 32SMALL-ASM-NEXT:    cmplwi 3, 3
 ; 32SMALL-ASM-NEXT:    bgt 0, L..BB0_3

llvm/test/CodeGen/PowerPC/jump-table.ll

 ; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64le-unknown-linux-gnu -stop-after=finalize-isel \
 ; RUN: | FileCheck %s
 ; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64-ibm-aix -stop-after=finalize-isel \
 ; RUN: | FileCheck %s
 ; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc-ibm-aix -stop-after=finalize-isel \
 ; RUN: | FileCheck %s
+; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64le-unknown-linux-gnu -stop-after=finalize-isel \
+; RUN: -min-jump-table-entries=4 | FileCheck %s
+; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64le-unknown-linux-gnu -stop-after=finalize-isel \
+; RUN: -ppc-min-jump-table-entries=4 | FileCheck %s -check-prefix=JT
+
+; JT:   jumpTable:
+; JT-NEXT:   kind:            label-difference32
+; JT-NEXT:   entries:
+; JT-NEXT:     - id:              0
 
-; CHECK:   jumpTable:
-; CHECK-NEXT:   kind:            label-difference32
-; CHECK-NEXT:   entries:
-; CHECK-NEXT:     - id:              0
+; CHECK-NOT: jumpTable:
 
 define signext i32 @jt(i32 signext %a, i32 signext %b) {
 entry:
   switch i32 %a, label %sw.epilog [
     i32 15, label %return
     i32 12, label %sw.bb1
     i32 19, label %sw.bb2
     i32 27, label %sw.bb3

llvm/test/CodeGen/PowerPC/jump-tables-collapse-rotate.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -o - \
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -ppc-min-jump-table-entries=4 -o - \
 ; RUN:   -ppc-asm-full-reg-names -verify-machineinstrs %s | FileCheck %s
 
 ; Function Attrs: nounwind
 define dso_local zeroext i32 @test(i32 signext %l) nounwind {
 ; CHECK-LABEL: test:
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    mflr r0
 ; CHECK-NEXT:    stdu r1, -32(r1)

llvm/test/CodeGen/PowerPC/mcm-5.ll

-; RUN: llc -verify-machineinstrs -mcpu=pwr7 -code-model=medium <%s | FileCheck %s
-; RUN: llc -verify-machineinstrs -mcpu=pwr7 -code-model=large <%s | FileCheck -check-prefix=LARGE  %s
+; RUN: llc -verify-machineinstrs -mcpu=pwr7 -ppc-min-jump-table-entries=4 -code-model=medium <%s | FileCheck %s
+; RUN: llc -verify-machineinstrs -mcpu=pwr7 -ppc-min-jump-table-entries=4 -code-model=large <%s | FileCheck -check-prefix=LARGE  %s
 
 ; Test correct code generation for medium and large code model
 ; for loading the address of a jump table from the TOC.
 
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"
 
 define signext i32 @test_jump_table(i32 signext %i) nounwind {

llvm/test/CodeGen/PowerPC/p10-spill-crgt.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
-; RUN:     -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-vsr-nums-as-vr < %s | \
+; RUN:     -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-vsr-nums-as-vr -ppc-min-jump-table-entries=4 < %s | \
 ; RUN:     FileCheck %s
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu \
-; RUN:     -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-vsr-nums-as-vr < %s | \
+; RUN:     -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-vsr-nums-as-vr -ppc-min-jump-table-entries=4 < %s | \
 ; RUN:     FileCheck %s --check-prefix=CHECK-BE
 
 ; This test case tests spilling the CR GT bit on Power10. On Power10, this is
 ; achieved by setb %reg, %CRREG (gt bit) -> stw %reg, $FI instead of:
 ; mfocrf %reg, %CRREG -> rlwinm %reg1, %reg, $SH, 0, 0 -> stw %reg1, $FI.
 
 ; Without fine-grained control over clobbering individual CR bits,
 ; it is difficult to produce a concise test case that will ensure a specific

llvm/test/CodeGen/PowerPC/pcrel-jump-table.ll

 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
-; RUN:   -mcpu=pwr10 -ppc-asm-full-reg-names < %s | FileCheck %s \
+; RUN:   -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-min-jump-table-entries=4 < %s | FileCheck %s \
 ; RUN:   --check-prefix=CHECK-R
 ; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
-; RUN:   -mcpu=pwr10 -ppc-use-absolute-jumptables \
+; RUN:   -mcpu=pwr10 -ppc-use-absolute-jumptables -ppc-min-jump-table-entries=4 \
 ; RUN:   -ppc-asm-full-reg-names < %s | FileCheck %s \
 ; RUN:   --check-prefix=CHECK-A-LE
 ; RUN: llc -verify-machineinstrs -target-abi=elfv2 -mtriple=powerpc64-- \
-; RUN:   -mcpu=pwr10 -ppc-asm-full-reg-names < %s | FileCheck %s \
+; RUN:   -mcpu=pwr10 -ppc-asm-full-reg-names -ppc-min-jump-table-entries=4 < %s | FileCheck %s \
 ; RUN:   --check-prefix=CHECK-R
 ; RUN: llc -verify-machineinstrs -target-abi=elfv2 -mtriple=powerpc64-- \
-; RUN:   -mcpu=pwr10 -ppc-use-absolute-jumptables \
+; RUN:   -mcpu=pwr10 -ppc-use-absolute-jumptables -ppc-min-jump-table-entries=4 \
 ; RUN:   -ppc-asm-full-reg-names < %s | FileCheck %s \
 ; RUN:   --check-prefix=CHECK-A-BE
 
 
 ; This test checks for getting relative and absolute jump table base address
 ; using PC Relative addressing.
 
 define dso_local signext i32 @jumptable(i32 signext %param) {

llvm/test/CodeGen/PowerPC/ppc-TOC-stats.ll

 ;;  Note: The checks for this test are manually generated. Please do not
 ;;        run a script to update these checks.
 
 ; REQUIRES: asserts
 
 ; RUN: llc -verify-machineinstrs -mtriple powerpc-ibm-aix-xcoff -mcpu=pwr8 \
-; RUN:   --stats < %s 2>&1 | FileCheck %s --check-prefix=AIX
+; RUN:   --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=AIX
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64-ibm-aix-xcoff -mcpu=pwr8 \
-; RUN:   --stats < %s 2>&1 | FileCheck %s --check-prefix=AIX
+; RUN:   --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=AIX
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64-unknown-linux -mcpu=pwr8 \
-; RUN:   --stats < %s 2>&1 | FileCheck %s --check-prefix=LINUX
+; RUN:   --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=LINUX
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64le-unknown-linux -mcpu=pwr8 \
-; RUN:   --stats < %s 2>&1 | FileCheck %s --check-prefix=LINUX
+; RUN:   --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=LINUX
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64-unknown-linux -mcpu=pwr8 \
-; RUN:   -code-model=large --stats < %s 2>&1 | FileCheck %s --check-prefix=LINUXLARGE
+; RUN:   -code-model=large --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=LINUXLARGE
 ; RUN: llc -verify-machineinstrs -mtriple powerpc64le-unknown-linux -mcpu=pwr8 \
-; RUN:   -code-model=large --stats < %s 2>&1 | FileCheck %s --check-prefix=LINUXLARGE
+; RUN:   -code-model=large --stats -ppc-min-jump-table-entries=4 < %s 2>&1 | FileCheck %s --check-prefix=LINUXLARGE
 
 
 ; The purpose of this test is to check that the statistics about the TOC are
 ; are collected correctly. This test tries to have all of the different types 
 ; of TOC entries.
 
 ; AIX: Statistics Collected
 ; AIX:   1 asmprinter           - Number of Block Address TOC Entries.

llvm/test/CodeGen/PowerPC/pr22711.ll

 ; Verify that the .toc section is aligned on an 8-byte boundary.
 
-; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 -filetype=obj -o - | llvm-readobj --sections - | FileCheck %s
+; RUN: llc -verify-machineinstrs < %s -mtriple=powerpc64-unknown-linux-gnu \
+; RUN: -mcpu=pwr8 -filetype=obj -ppc-min-jump-table-entries=4 -o - | llvm-readobj --sections - | FileCheck %s
 
 define void @test(ptr %a) {
 entry:
   %a.addr = alloca ptr, align 8
   store ptr %a, ptr %a.addr, align 8
   %0 = load ptr,  ptr %a.addr, align 8
   %incdec.ptr = getelementptr inbounds i32, ptr %0, i32 1
   store ptr %incdec.ptr, ptr %a.addr, align 8

llvm/test/CodeGen/PowerPC/pr33547.ll

L.entry:
   %0 = load i32, ptr %i, align 4
   ret i32 %0
 }
 
 ; Function Attrs: noinline norecurse nounwind
 define void @testFunc(ptr nocapture %r, ptr nocapture readonly %k) {
 ; CHECK-LABEL: testFunc:
 ; CHECK:       # %bb.0: # %L.entry
-; CHECK-NEXT:    mflr 0
-; CHECK-NEXT:    stdu 1, -32(1)
-; CHECK-NEXT:    std 0, 48(1)
-; CHECK-NEXT:    .cfi_def_cfa_offset 32
-; CHECK-NEXT:    .cfi_offset lr, 16
-; CHECK-NEXT:    bl .L2$pb
-; CHECK-NEXT:  .L2$pb:
-; CHECK-NEXT:    lwz 4, 0(4)
-; CHECK-NEXT:    mflr 5
-; CHECK-NEXT:    addi 4, 4, -1
-; CHECK-NEXT:    cmplwi 4, 5
-; CHECK-NEXT:    bgt 0, .LBB2_6
-; CHECK-NEXT:  # %bb.1: # %L.entry
-; CHECK-NEXT:    addis 6, 2, .LC2@toc@ha
-; CHECK-NEXT:    rldic 4, 4, 2, 30
-; CHECK-NEXT:    ld 6, .LC2@toc@l(6)
-; CHECK-NEXT:    lwax 4, 4, 6
-; CHECK-NEXT:    add 4, 4, 5
-; CHECK-NEXT:    mtctr 4
+; CHECK-NEXT:    lwz 5, 0(4)
 ; CHECK-NEXT:    li 4, -3
-; CHECK-NEXT:    bctr
+; CHECK-NEXT:    cmpwi 5, 4
+; CHECK-NEXT:    bge 0, .LBB2_6
+; CHECK-NEXT:  # %bb.1: # %L.entry
+; CHECK-NEXT:    cmplwi 5, 1
+; CHECK-NEXT:    beq 0, .LBB2_11
+; CHECK-NEXT:  # %bb.2: # %L.entry
+; CHECK-NEXT:    cmplwi 5, 2
+; CHECK-NEXT:    beq 0, .LBB2_5
+; CHECK-NEXT:  # %bb.3: # %L.entry
+; CHECK-NEXT:    cmplwi 5, 3
+; CHECK-NEXT:    beq 0, .LBB2_11
+; CHECK-NEXT:  # %bb.4: # %L.LB3_307
+; CHECK-NEXT:    blr
 ; CHECK-NEXT:    .p2align 4
-; CHECK-NEXT:  .LBB2_2: # %infloop11
+; CHECK-NEXT:  .LBB2_5: # %infloop11
 ; CHECK-NEXT:    #
-; CHECK-NEXT:    b .LBB2_2
+; CHECK-NEXT:    b .LBB2_5
+; CHECK-NEXT:  .LBB2_6: # %L.entry
+; CHECK-NEXT:    beq 0, .LBB2_10
+; CHECK-NEXT:  # %bb.7: # %L.entry
+; CHECK-NEXT:    cmplwi 5, 5
+; CHECK-NEXT:    beq 0, .LBB2_11
+; CHECK-NEXT:  # %bb.8: # %L.entry
+; CHECK-NEXT:    cmplwi 5, 6
+; CHECK-NEXT:    bnelr 0
 ; CHECK-NEXT:    .p2align 4
-; CHECK-NEXT:  .LBB2_3: # %infloop
+; CHECK-NEXT:  .LBB2_9: # %infloop
 ; CHECK-NEXT:    #
-; CHECK-NEXT:    b .LBB2_3
-; CHECK-NEXT:  .LBB2_4: # %L.LB3_321.split
+; CHECK-NEXT:    b .LBB2_9
+; CHECK-NEXT:  .LBB2_10: # %L.LB3_321.split
 ; CHECK-NEXT:    li 4, 5
-; CHECK-NEXT:  .LBB2_5: # %L.LB3_307.sink.split
+; CHECK-NEXT:  .LBB2_11: # %L.LB3_307.sink.split
 ; CHECK-NEXT:    stw 4, 0(3)
-; CHECK-NEXT:  .LBB2_6: # %L.LB3_307
-; CHECK-NEXT:    addi 1, 1, 32
-; CHECK-NEXT:    ld 0, 16(1)
-; CHECK-NEXT:    mtlr 0
 ; CHECK-NEXT:    blr
 L.entry:
   %0 = load i32, ptr %k, align 4
   switch i32 %0, label %L.LB3_307 [
     i32 1, label %L.LB3_307.sink.split
     i32 3, label %L.LB3_307.sink.split
     i32 4, label %L.LB3_321.split
     i32 5, label %L.LB3_307.sink.split

llvm/test/CodeGen/PowerPC/unreachable-mbb-jtreference-elimination.ll

-; RUN: llc -O2 --verify-machineinstrs -stop-before=livevars \
+; RUN: llc -O2 --verify-machineinstrs -stop-before=livevars -ppc-min-jump-table-entries=4 \
 ; RUN:   -mtriple=powerpc64le-unknown-unknown < %s | FileCheck %s
 
 define dso_local void @foo() #0 {
 ; CHECK-LABEL: fixedStack:
 ; CHECK-NEXT:  stack: []
 ; CHECK-NEXT:  entry_values: []
 ; CHECK-NEXT:  callSites: []
 ; CHECK-NEXT:  debugValueSubstitutions: []