arch-gcn3: implement instruction s_setreg_b32

Instruction s_setreg_b32 was unimplemented, but is used by hipified
rodinia 'srad'. The instruction sets values of hardware internal
registers. If the instruction is writing into MODE to control
single-precision FP round and denorm modes, a simple warn will be
printed; for all other cases (non-MODE hw register or other
precisions), panic will happen.

Change-Id: Idb1cd5f60548a146bc980f1a27faff30259e74ce
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29949
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Xianwei Zhang <xianwei.zhang@amd.com>

diff --git a/src/arch/gcn3/insts/instructions.cc b/src/arch/gcn3/insts/instructions.cc
index 6ffd049f26b8374add23243a8d513290b6e1b86d..8b72e0da163537182015f6193168006b7510cb61 100644 (file)
--- a/src/arch/gcn3/insts/instructions.cc
+++ b/src/arch/gcn3/insts/instructions.cc
@@ -1800,6 +1800,7 @@ namespace Gcn3ISA
     Inst_SOPK__S_SETREG_B32::Inst_SOPK__S_SETREG_B32(InFmt_SOPK *iFmt)
         : Inst_SOPK(iFmt, "s_setreg_b32")
     {
+        setFlag(ALU);
     } // Inst_SOPK__S_SETREG_B32
 
     Inst_SOPK__S_SETREG_B32::~Inst_SOPK__S_SETREG_B32()
@@ -1813,6 +1814,32 @@ namespace Gcn3ISA
     void
     Inst_SOPK__S_SETREG_B32::execute(GPUDynInstPtr gpuDynInst)
     {
+        ScalarRegI16 simm16 = instData.SIMM16;
+        ScalarRegU32 hwregId = simm16 & 0x3f;
+        ScalarRegU32 offset = (simm16 >> 6) & 31;
+        ScalarRegU32 size = ((simm16 >> 11) & 31) + 1;
+
+        ScalarOperandU32 hwreg(gpuDynInst, hwregId);
+        ScalarOperandU32 sdst(gpuDynInst, instData.SDST);
+        hwreg.read();
+        sdst.read();
+
+        // Store value from SDST to part of the hardware register.
+        ScalarRegU32 mask = (((1U << size) - 1U) << offset);
+        hwreg = ((hwreg.rawData() & ~mask)
+                        | ((sdst.rawData() << offset) & mask));
+        hwreg.write();
+
+        // set MODE register to control the behavior of single precision
+        // floating-point numbers: denormal mode or round mode
+        if (hwregId==1 && size==2
+                        && (offset==4 || offset==0)) {
+            warn_once("Be cautious that s_setreg_b32 has no real effect "
+                            "on FP modes: %s\n", gpuDynInst->disassemble());
+            return;
+        }
+
+        // panic if not changing MODE of floating-point numbers
         panicUnimplemented();
     }