[flang][cuda] Correct the number of blocks when setting the grid to * (llvm#121000)

We set the `gridX` argument of `_FortranACUFLaunchKernel` to `-1` when
`*` is passed to the grid parameter. We store it in one of `dim3`
members. However, `dim3` members are unsigned, so positive-value checks
we use later, such as `gridDim.x > 0`, are invalid. This PR utilizes the
original gird-size arguments to compute the number of blocks.

Author: khaki3

flang/runtime/CUDA/kernel.cpp

@@ -48,13 +48,13 @@ void RTDEF(CUFLaunchKernel)(const void *kernel, intptr_t gridX, intptr_t gridY,
       maxBlocks = multiProcCount * maxBlocks;
     }
     if (maxBlocks > 0) {
-      if (gridDim.x > 0) {
+      if (gridX > 0) {
         maxBlocks = maxBlocks / gridDim.x;
       }
-      if (gridDim.y > 0) {
+      if (gridY > 0) {
         maxBlocks = maxBlocks / gridDim.y;
       }
-      if (gridDim.z > 0) {
+      if (gridZ > 0) {
         maxBlocks = maxBlocks / gridDim.z;
       }
       if (maxBlocks < 1) {
@@ -113,13 +113,13 @@ void RTDEF(CUFLaunchClusterKernel)(const void *kernel, intptr_t clusterX,
       maxBlocks = multiProcCount * maxBlocks;
     }
     if (maxBlocks > 0) {
-      if (config.gridDim.x > 0) {
+      if (gridX > 0) {
         maxBlocks = maxBlocks / config.gridDim.x;
       }
-      if (config.gridDim.y > 0) {
+      if (gridY > 0) {
         maxBlocks = maxBlocks / config.gridDim.y;
       }
-      if (config.gridDim.z > 0) {
+      if (gridZ > 0) {
         maxBlocks = maxBlocks / config.gridDim.z;
       }
       if (maxBlocks < 1) {