This patch fixes the Altivec addend construction for the fused multiply-add

instruction (vmaddfp) to conform with IEEE to ensure the sign of a zero
result when resulting product is -0.0.

The -0.0 vector addend to vmaddfp is generated by a creating a vector
with full bits sets and then shifting each elements by 31-bits to the
left, resulting in a vector of 0x80000000 (or -0.0 as float).

The 'buildvec_canonicalize.ll' was adjusted to reflect this change and
the 'vec_mul.ll' was complemented with the float vector multiplication
test.

llvm-svn: 168998

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrAltivec.td b/llvm/lib/Target/PowerPC/PPCInstrAltivec.td
index 87758e90fbd..0cf28ae4b5c 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrAltivec.td
+++ b/llvm/lib/Target/PowerPC/PPCInstrAltivec.td
@@ -158,10 +158,6 @@ def vecspltisw : PatLeaf<(build_vector), [{
   return PPC::get_VSPLTI_elt(N, 4, *CurDAG).getNode() != 0;
 }], VSPLTISW_get_imm>;
 
-def V_immneg0 : PatLeaf<(build_vector), [{
-  return PPC::isAllNegativeZeroVector(N);
-}]>;
-
 //===----------------------------------------------------------------------===//
 // Helpers for defining instructions that directly correspond to intrinsics.
 
@@ -585,7 +581,12 @@ def VCMPGTUWo : VCMPo<646, "vcmpgtuw. $vD, $vA, $vB", v4i32>;
 def V_SET0 : VXForm_setzero<1220, (outs VRRC:$vD), (ins),
                       "vxor $vD, $vD, $vD", VecFP,
                       [(set VRRC:$vD, (v4i32 immAllZerosV))]>;
+let IMM=-1 in {
+def V_SETALLONES : VXForm_3<908, (outs VRRC:$vD), (ins),
+                      "vspltisw $vD, -1", VecFP,
+                      [(set VRRC:$vD, (v4i32 immAllOnesV))]>;
 }
+} // VALU Operations.
 
 //===----------------------------------------------------------------------===//
 // Additional Altivec Patterns
@@ -672,7 +673,8 @@ def : Pat<(v4i32 (and VRRC:$A, (vnot_ppc VRRC:$B))),
           (VANDC VRRC:$A, VRRC:$B)>;
 
 def : Pat<(fmul VRRC:$vA, VRRC:$vB),
-          (VMADDFP VRRC:$vA, VRRC:$vB, (v4i32 (V_SET0)))>; 
+          (VMADDFP VRRC:$vA, VRRC:$vB,
+             (v4i32 (VSLW (V_SETALLONES), (V_SETALLONES))))>; 
 
 // Fused multiply add and multiply sub for packed float.  These are represented
 // separately from the real instructions above, for operations that must have