[PPC] Avoid incorrect fp-i128-fp lowering.

Summary:
Fix an issue that's similar to what D41411 fixed:
  float(__int128(float_var)) shouldn't be optimized to xscvdpsxds +
  xscvsxdsp, as they mean (float)(int64_t)float_var.

Reviewers: jtony, hfinkel, echristo

Subscribers: sanjoy, nemanjai, hiraditya, llvm-commits, kbarton

Differential Revision: https://reviews.llvm.org/D42400

llvm-svn: 323270

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/fp-int128-fp-combine.ll b/llvm/test/CodeGen/PowerPC/fp-int128-fp-combine.ll
new file mode 100644
index 00000000000..eff0c28e0f5
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/fp-int128-fp-combine.ll
@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -O0 -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
+
+; xscvdpsxds should NOT be emitted, since it saturates the result down to i64.
+define float @f_i128_f(float %v) {
+; CHECK-LABEL: f_i128_f:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    mflr 0
+; CHECK-NEXT:    std 0, 16(1)
+; CHECK-NEXT:    stdu 1, -32(1)
+; CHECK-NEXT:    .cfi_def_cfa_offset 32
+; CHECK-NEXT:    .cfi_offset lr, 16
+; CHECK-NEXT:    bl __fixsfti
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    bl __floattisf
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    addi 1, 1, 32
+; CHECK-NEXT:    ld 0, 16(1)
+; CHECK-NEXT:    mtlr 0
+; CHECK-NEXT:    blr
+entry:
+  %a = fptosi float %v to i128
+  %b = sitofp i128 %a to float
+  ret float %b
+}