Index: lib/Target/AMDGPU/SMInstructions.td
===================================================================
--- lib/Target/AMDGPU/SMInstructions.td
+++ lib/Target/AMDGPU/SMInstructions.td
@@ -81,6 +81,18 @@
   let ScalarStore = 1;
 }
 
+class SM_Discard_Pseudo <string opName, dag ins, bit isImm>
+  : SM_Pseudo<opName, (outs), ins, " $sbase, $offset"> {
+  let mayLoad = 0;
+  let mayStore = 0;
+  let has_glc = 0;
+  let has_sdst = 0;
+  let ScalarStore = 0;
+  let hasSideEffects = 1;
+  let offset_is_imm = isImm;
+  let PseudoInstr = opName # !if(isImm, "_IMM", "_SGPR");
+}
+
 multiclass SM_Pseudo_Loads<string opName,
                            RegisterClass baseClass,
                            RegisterClass dstClass> {
@@ -125,6 +137,11 @@
   }
 }
 
+multiclass SM_Pseudo_Discards<string opName> {
+  def _IMM  : SM_Discard_Pseudo <opName, (ins SReg_64:$sbase, smrd_offset_20:$offset), 1>;
+  def _SGPR : SM_Discard_Pseudo <opName, (ins SReg_64:$sbase, SReg_32:$offset), 0>;
+}
+
 class SM_Time_Pseudo<string opName, SDPatternOperator node> : SM_Pseudo<
   opName, (outs SReg_64_XEXEC:$sdst), (ins),
   " $sdst", [(set i64:$sdst, (node))]> {
@@ -332,6 +349,11 @@
 
 } // let SubtargetPredicate = HasScalarAtomics
 
+let SubtargetPredicate = isGFX9 in {
+defm S_DCACHE_DISCARD    : SM_Pseudo_Discards <"s_dcache_discard">;
+defm S_DCACHE_DISCARD_X2 : SM_Pseudo_Discards <"s_dcache_discard_x2">;
+}
+
 //===----------------------------------------------------------------------===//
 // Scalar Memory Patterns
 //===----------------------------------------------------------------------===//
@@ -636,6 +658,14 @@
 defm S_ATOMIC_INC_X2              : SM_Real_Atomics_vi <0xab, "S_ATOMIC_INC_X2">;
 defm S_ATOMIC_DEC_X2              : SM_Real_Atomics_vi <0xac, "S_ATOMIC_DEC_X2">;
 
+multiclass SM_Real_Discard_vi<bits<8> op, string ps> {
+  def _IMM_vi  : SMEM_Real_vi <op, !cast<SM_Discard_Pseudo>(ps#_IMM)>;
+  def _SGPR_vi : SMEM_Real_vi <op, !cast<SM_Discard_Pseudo>(ps#_SGPR)>;
+}
+
+defm S_DCACHE_DISCARD    : SM_Real_Discard_vi <0x28, "S_DCACHE_DISCARD">;
+defm S_DCACHE_DISCARD_X2 : SM_Real_Discard_vi <0x29, "S_DCACHE_DISCARD_X2">;
+
 //===----------------------------------------------------------------------===//
 // CI
 //===----------------------------------------------------------------------===//
Index: test/MC/AMDGPU/smem.s
===================================================================
--- test/MC/AMDGPU/smem.s
+++ test/MC/AMDGPU/smem.s
@@ -214,6 +214,26 @@
 // NOSICIVI: error
 
 //===----------------------------------------------------------------------===//
+// s_dcache_discard instructions
+//===----------------------------------------------------------------------===//
+
+s_dcache_discard s[2:3], s0
+// GFX9:     s_dcache_discard s[2:3], s0 ; encoding: [0x01,0x00,0xa0,0xc0,0x00,0x00,0x00,0x00]
+// NOSICIVI: error: instruction not supported on this GPU
+
+s_dcache_discard s[2:3], 0x0
+// GFX9:     s_dcache_discard s[2:3], 0x0 ; encoding: [0x01,0x00,0xa2,0xc0,0x00,0x00,0x00,0x00]
+// NOSICIVI: error: instruction not supported on this GPU
+
+s_dcache_discard_x2 s[2:3], s101
+// GFX9:     s_dcache_discard_x2 s[2:3], s101 ; encoding: [0x01,0x00,0xa4,0xc0,0x65,0x00,0x00,0x00]
+// NOSICIVI: error: instruction not supported on this GPU
+
+s_dcache_discard_x2 s[2:3], 0x0
+// GFX9:     s_dcache_discard_x2 s[2:3], 0x0 ; encoding: [0x01,0x00,0xa6,0xc0,0x00,0x00,0x00,0x00]
+// NOSICIVI: error: instruction not supported on this GPU
+
+//===----------------------------------------------------------------------===//
 // s_atomic instructions
 //===----------------------------------------------------------------------===//
 
Index: test/MC/Disassembler/AMDGPU/smem_gfx9.txt
===================================================================
--- test/MC/Disassembler/AMDGPU/smem_gfx9.txt
+++ test/MC/Disassembler/AMDGPU/smem_gfx9.txt
@@ -32,6 +32,22 @@
 0x02,0x01,0x5d,0xc0,0x00,0x00,0x00,0x00
 
 #===------------------------------------------------------------------------===#
+# s_dcache_discard
+#===------------------------------------------------------------------------===#
+
+# GFX9: s_dcache_discard s[100:101], s0 ; encoding: [0x32,0x00,0xa0,0xc0,0x00,0x00,0x00,0x00]
+0x32,0x00,0xa0,0xc0,0x00,0x00,0x00,0x00
+
+# GFX9: s_dcache_discard s[2:3], 0x0 ; encoding: [0x01,0x00,0xa2,0xc0,0x00,0x00,0x00,0x00]
+0x01,0x00,0xa2,0xc0,0x00,0x00,0x00,0x00
+
+# GFX9: s_dcache_discard_x2 s[2:3], s101 ; encoding: [0x01,0x00,0xa4,0xc0,0x65,0x00,0x00,0x00]
+0x01,0x00,0xa4,0xc0,0x65,0x00,0x00,0x00
+
+# GFX9: s_dcache_discard_x2 s[2:3], 0x0 ; encoding: [0x01,0x00,0xa6,0xc0,0x00,0x00,0x00,0x00]
+0x01,0x00,0xa6,0xc0,0x00,0x00,0x00,0x00
+
+#===------------------------------------------------------------------------===#
 # s_atomic
 #===------------------------------------------------------------------------===#