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

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.

Differential Revision: https://reviews.llvm.org/D107914

Author: amy-kwan

llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp

@@ -485,6 +485,9 @@ bool PPCTTIImpl::mightUseCTR(BasicBlock *BB, TargetLibraryInfo *LibInfo,
           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())

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

@@ -0,0 +1,113 @@
+; 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
+}