Guard against division by zero for no VGPR usage (e.g., in an empty kernel) (#1528)

* guard against division by zero for no VGPR usage (e.g., in an empty kernel)

* fix bracket format

* clean up parenthesis


[ROCm/clr commit: d16963c9d5]

projects/clr/hipamd/src/hip_module.cpp

@@ -1326,17 +1326,18 @@ hipError_t ihipOccupancyMaxActiveBlocksPerMultiprocessor(
     size_t numWavefronts = (blockSize + wavefrontSize - 1) / wavefrontSize;
 
     size_t availableVGPRs = (prop.regsPerBlock / wavefrontSize / simdPerCU);
-    size_t vgprs_alu_occupancy = simdPerCU * std::min(maxWavesPerSimd, availableVGPRs / usedVGPRS);
+    size_t vgprs_alu_occupancy = simdPerCU * (usedVGPRS == 0 ? maxWavesPerSimd
+        : std::min(maxWavesPerSimd, availableVGPRs / usedVGPRS));
 
     // Calculate blocks occupancy per CU based on VGPR usage
     *numBlocks = vgprs_alu_occupancy / numWavefronts;
 
     const size_t availableSGPRs = (prop.gcnArch < 800) ? 512 : 800;
-    size_t sgprs_alu_occupancy = simdPerCU * ((usedSGPRS == 0) ? maxWavesPerSimd
+    size_t sgprs_alu_occupancy = simdPerCU * (usedSGPRS == 0 ? maxWavesPerSimd
         : std::min(maxWavesPerSimd, availableSGPRs / usedSGPRS));
 
     // Calculate blocks occupancy per CU based on SGPR usage
-    *numBlocks = std::min(*numBlocks, (uint32_t) (sgprs_alu_occupancy / numWavefronts)); 
+    *numBlocks = std::min(*numBlocks, (uint32_t) (sgprs_alu_occupancy / numWavefronts));
 
     size_t total_used_lds = usedLDS + dynSharedMemPerBlk;
     if (total_used_lds != 0) {