[PATCH] Fix VGATHER* operand constraints

Add earlyclobber constaints to prevent input register being allocated as
the output register because, according to Intel spec [1], "If any pair
of the index, mask, or destination registers are the same, this
instruction results a UD fault."

---
[1] http://software.intel.com/sites/default/files/319433-014.pdf



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183327 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 5 insertions, 1 deletions

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 02f5fe4952..14ec2ddb4e 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2041,6 +2041,8 @@ SDNode *X86DAGToDAGISel::Select(SDNode *Node) {
     case Intrinsic::x86_avx2_gather_d_d_256:
     case Intrinsic::x86_avx2_gather_q_d:
     case Intrinsic::x86_avx2_gather_q_d_256: {
+      if (!Subtarget->hasAVX2())
+        break;
       unsigned Opc;
       switch (IntNo) {
       default: llvm_unreachable("Impossible intrinsic");
diff --git a/lib/Target/X86/X86InstrSSE.td b/lib/Target/X86/X86InstrSSE.td
index cce7788fb3..a1d3e81311 100644
--- a/lib/Target/X86/X86InstrSSE.td
+++ b/lib/Target/X86/X86InstrSSE.td
@@ -8372,7 +8372,9 @@ multiclass avx2_gather<bits<8> opc, string OpcodeStr, RegisterClass RC256,
             []>, VEX_4VOp3, VEX_L;
 }
 
-let mayLoad = 1, Constraints = "$src1 = $dst, $mask = $mask_wb" in {
+let mayLoad = 1, Constraints
+  = "@earlyclobber $dst,@earlyclobber $mask_wb, $src1 = $dst, $mask = $mask_wb"
+  in {
   defm VGATHERDPD : avx2_gather<0x92, "vgatherdpd", VR256, vx64mem, vx64mem>, VEX_W;
   defm VGATHERQPD : avx2_gather<0x93, "vgatherqpd", VR256, vx64mem, vy64mem>, VEX_W;
   defm VGATHERDPS : avx2_gather<0x92, "vgatherdps", VR256, vx32mem, vy32mem>;