[PATCH] D42400: [PPC] Avoid incorrect fp-i128-fp lowering.

[Tim Shen via Phabricator via llvm-commits]

timshen created this revision.
timshen added reviewers: jtony, hfinkel, echristo.
Herald added subscribers: kbarton, hiraditya, nemanjai, sanjoy.

Fix an issue that's similar to what https://reviews.llvm.org/D41411 fixed:

  float(__int128(float_var)) shouldn't be optimized to xscvdpsxds +
  xscvsxdsp, as they mean (float)(int64_t)float_var.


https://reviews.llvm.org/D42400

Files:
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/test/CodeGen/PowerPC/fp-int128-fp-combine.ll


Index: llvm/test/CodeGen/PowerPC/fp-int128-fp-combine.ll
===================================================================
--- /dev/null
+++ 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
+}
Index: llvm/lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -11948,10 +11948,12 @@
   SDLoc dl(N);
   SDValue Op(N, 0);
 
-  // Don't handle ppc_fp128 here or i1 conversions.
+  // Don't handle ppc_fp128 here or conversions that are out-of-range capable
+  // from the hardware.
   if (Op.getValueType() != MVT::f32 && Op.getValueType() != MVT::f64)
     return SDValue();
-  if (Op.getOperand(0).getValueType() == MVT::i1)
+  if (Op.getOperand(0).getValueType().getSimpleVT() <= MVT(MVT::i1) ||
+      Op.getOperand(0).getValueType().getSimpleVT() > MVT(MVT::i64))
     return SDValue();
 
   SDValue FirstOperand(Op.getOperand(0));


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