[PowerPC] Disable CTR Loop generate for fma with the PPC double double type.

[amyk]

Summary

It is possible to generate the llvm.fmuladd.ppcf128 intrinsic, and there is no actual
FMA instruction that corresponds to this intrinsic call for ppcf128. Thus, this
intrinsic needs to remain as a call as it cannot be lowered to any instruction, which
also means we need to disable CTR loop generation for fma involving the ppcf128 type.
This patch accomplishes this behaviour.

[amyk]

Address clang-format comment for PPCTargetTransformInfo.cpp.

[shchenz]

llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp

462

Enable/disable CTR loop generation can not make sure the Intrinsic::fmuladd be kept as a call. Can we move these lines to line 500?

llvm/test/CodeGen/PowerPC/disable-ctr-ppcf128.ll

150

Can we narrow down the case a little bit? maybe one call is enough?

[amyk]

Address review comments:

• Move case the fmuladd lower in mightUseCTR.
• Shorten test case to one llvm.fmuladd.ppcf128 intrinsic call.

[shchenz]

Look good to me except for some minor comments for the test cases part.

llvm/test/CodeGen/PowerPC/disable-ctr-ppcf128.ll

17

Is it necessary to test we don't generate a CTR loop?

22

none of these args are used in the function body, so I think they can be removed and the type definition for %0, %1, %2, %3 can also be removed?

22

We can also removed the unnecessary function attributes like linkonce_odr hidden local_unnamed_addr and local_unnamed_addr?

[amyk]

Clean up test case a little more - removing unnecessary function attributes/arguments.

[amyk]

@shchenz I've cleaned up the test case a little bit more by removing the attributes and arguments (that I realized we were not utilizing). Thanks for catching these details! :-)

llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp

if (CallInst *CI = dyn_cast<CallInst>(J)) {
                 isLargeIntegerTy(!TM.isPPC64(), SrcType) ||
                 isLargeIntegerTy(!TM.isPPC64(), DstType))
               return true;
             break;
           }
 
           // Exclude eh_sjlj_setjmp; we don't need to exclude eh_sjlj_longjmp
           // because, although it does clobber the counter register, the
           // control can't then return to inside the loop unless there is also
           // an eh_sjlj_setjmp.
           case Intrinsic::eh_sjlj_setjmp:
 
           case Intrinsic::memcpy:
           case Intrinsic::memmove:
           case Intrinsic::memset:
           case Intrinsic::powi:
           case Intrinsic::log:
if (CallInst *CI = dyn_cast<CallInst>(J)) {
           case Intrinsic::experimental_constrained_log2:
           case Intrinsic::experimental_constrained_log10:
           case Intrinsic::experimental_constrained_exp:
           case Intrinsic::experimental_constrained_exp2:
           case Intrinsic::experimental_constrained_pow:
           case Intrinsic::experimental_constrained_sin:
           case Intrinsic::experimental_constrained_cos:
             return true;
+          // There is no corresponding FMA instruction for PPC double double.
+          // Thus, we need to disable CTR loop generation for this type.
+          case Intrinsic::fmuladd:
           case Intrinsic::copysign:
             if (CI->getArgOperand(0)->getType()->getScalarType()->
                 isPPC_FP128Ty())
               return true;
             else
               continue; // ISD::FCOPYSIGN is never a library call.
           case Intrinsic::fma:                Opcode = ISD::FMA;        break;
           case Intrinsic::sqrt:               Opcode = ISD::FSQRT;      break;

llvm/test/CodeGen/PowerPC/disable-ctr-ppcf128.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mcpu=pwr9 -verify-machineinstrs -ppc-asm-full-reg-names \
+; RUN:    -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s --check-prefix=LE
+; RUN: llc -mcpu=pwr9 -verify-machineinstrs -ppc-asm-full-reg-names \
+; RUN:    -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s --check-prefix=P9BE
+; RUN: llc -mcpu=pwr8 -verify-machineinstrs -ppc-asm-full-reg-names \
+; RUN:    -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s --check-prefix=LE
+; RUN: llc -mcpu=pwr8 -verify-machineinstrs -ppc-asm-full-reg-names \
+; RUN:    -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s --check-prefix=P8BE
+
+declare ppc_fp128 @llvm.fmuladd.ppcf128(ppc_fp128, ppc_fp128, ppc_fp128) #2
+
+define ppc_fp128 @test_ctr0() {
+; LE-LABEL: test_ctr0:
+; LE:       # %bb.0: # %bb
+; LE-NEXT:    mflr r0
+; LE-NEXT:    .cfi_def_cfa_offset 48
+; LE-NEXT:    .cfi_offset lr, 16
+; LE-NEXT:    .cfi_offset r30, -16
+; LE-NEXT:    std r30, -16(r1) # 8-byte Folded Spill
+; LE-NEXT:    std r0, 16(r1)
+; LE-NEXT:    stdu r1, -48(r1)
+; LE-NEXT:    xxlxor f1, f1, f1
+; LE-NEXT:    li r30, 0
+; LE-NEXT:    xxlxor f2, f2, f2
+; LE-NEXT:    .p2align 5
+; LE-NEXT:  .LBB0_1: # %bb6
+; LE-NEXT:    #
+; LE-NEXT:    xxlxor f3, f3, f3
+; LE-NEXT:    xxlxor f4, f4, f4
+; LE-NEXT:    bl __gcc_qadd
+; LE-NEXT:    nop
+; LE-NEXT:    addi r30, r30, 4
+; LE-NEXT:    cmpldi r30, 0
+; LE-NEXT:    bne cr0, .LBB0_1
+; LE-NEXT:  # %bb.2: # %bb14
+; LE-NEXT:    addi r1, r1, 48
+; LE-NEXT:    ld r0, 16(r1)
+; LE-NEXT:    ld r30, -16(r1) # 8-byte Folded Reload
+; LE-NEXT:    mtlr r0
+; LE-NEXT:    blr
+;
+; P9BE-LABEL: test_ctr0:
+; P9BE:       # %bb.0: # %bb
+; P9BE-NEXT:    mflr r0
+; P9BE-NEXT:    std r0, 16(r1)
+; P9BE-NEXT:    stdu r1, -128(r1)
+; P9BE-NEXT:    .cfi_def_cfa_offset 128
+; P9BE-NEXT:    .cfi_offset lr, 16
+; P9BE-NEXT:    .cfi_offset r30, -16
+; P9BE-NEXT:    std r30, 112(r1) # 8-byte Folded Spill
+; P9BE-NEXT:    xxlxor f1, f1, f1
+; P9BE-NEXT:    li r30, 0
+; P9BE-NEXT:    xxlxor f2, f2, f2
+; P9BE-NEXT:    .p2align 5
+; P9BE-NEXT:  .LBB0_1: # %bb6
+; P9BE-NEXT:    #
+; P9BE-NEXT:    xxlxor f3, f3, f3
+; P9BE-NEXT:    xxlxor f4, f4, f4
+; P9BE-NEXT:    bl __gcc_qadd
+; P9BE-NEXT:    nop
+; P9BE-NEXT:    addi r30, r30, 4
+; P9BE-NEXT:    cmpldi r30, 0
+; P9BE-NEXT:    bne cr0, .LBB0_1
+; P9BE-NEXT:  # %bb.2: # %bb14
+; P9BE-NEXT:    ld r30, 112(r1) # 8-byte Folded Reload
+; P9BE-NEXT:    addi r1, r1, 128
+; P9BE-NEXT:    ld r0, 16(r1)
+; P9BE-NEXT:    mtlr r0
+; P9BE-NEXT:    blr
+;
+; P8BE-LABEL: test_ctr0:
+; P8BE:       # %bb.0: # %bb
+; P8BE-NEXT:    mflr r0
+; P8BE-NEXT:    std r0, 16(r1)
+; P8BE-NEXT:    stdu r1, -128(r1)
+; P8BE-NEXT:    .cfi_def_cfa_offset 128
+; P8BE-NEXT:    .cfi_offset lr, 16
+; P8BE-NEXT:    .cfi_offset r30, -16
+; P8BE-NEXT:    xxlxor f1, f1, f1
+; P8BE-NEXT:    std r30, 112(r1) # 8-byte Folded Spill
+; P8BE-NEXT:    li r30, 0
+; P8BE-NEXT:    xxlxor f2, f2, f2
+; P8BE-NEXT:    .p2align 5
+; P8BE-NEXT:  .LBB0_1: # %bb6
+; P8BE-NEXT:    #
+; P8BE-NEXT:    xxlxor f3, f3, f3
+; P8BE-NEXT:    xxlxor f4, f4, f4
+; P8BE-NEXT:    bl __gcc_qadd
+; P8BE-NEXT:    nop
+; P8BE-NEXT:    addi r30, r30, 4
+; P8BE-NEXT:    cmpldi r30, 0
+; P8BE-NEXT:    bne cr0, .LBB0_1
+; P8BE-NEXT:  # %bb.2: # %bb14
+; P8BE-NEXT:    ld r30, 112(r1) # 8-byte Folded Reload
+; P8BE-NEXT:    addi r1, r1, 128
+; P8BE-NEXT:    ld r0, 16(r1)
+; P8BE-NEXT:    mtlr r0
+; P8BE-NEXT:    blr
+bb:
+  br label %bb6
+
+bb6:                                              ; preds = %bb6, %bb
+  %i = phi ppc_fp128 [ %i8, %bb6 ], [ 0xM00000000000000000000000000000000, %bb ]
+  %i7 = phi i64 [ %i9, %bb6 ], [ 0, %bb ]
+  %i8 = tail call ppc_fp128 @llvm.fmuladd.ppcf128(ppc_fp128 0xM00000000000000000000000000000000, ppc_fp128 0xM00000000000000000000000000000000, ppc_fp128 %i) #4
+  %i9 = add i64 %i7, -4
+  %i10 = icmp eq i64 %i9, 0
+  br i1 %i10, label %bb14, label %bb6
+
+bb14:                                             ; preds = %bb6
+  ret ppc_fp128 %i8
+}