[OPTIMIZER] Coalesce pass no longer takes a num-warps argument (#99)

Improved design to avoid inconsistent `num-warps` value between the pass and the parent module of the operation it processes.

lib/Conversion/TritonGPUToLLVM/TritonGPUToLLVM.cpp

@@ -795,24 +795,6 @@ private:
   AxisInfoAnalysis &AxisAnalysisPass;
 };
 
-// Extract numWarps information from TritonGPU module, return 0 if failed.
-// This is a naive implementation, it assumes that all the blocked layout should
-// have the same numWarps setting in a module, it just find a blocked layout
-// encoding and return the warpsPerCTA field.
-int extractNumWarps(mlir::ModuleOp module) {
-  int numWarps{};
-  if (module->hasAttr(AttrNumWarpsName))
-    numWarps = module->getAttr(AttrNumWarpsName)
-                   .dyn_cast<IntegerAttr>()
-                   .getValue()
-                   .getZExtValue();
-  else
-    llvm::report_fatal_error(
-        "TritonGPU module should contain a triton_gpu.num-warps attribute");
-
-  return numWarps;
-}
-
 struct BroadcastOpConversion
     : public ConvertTritonGPUOpToLLVMPattern<triton::BroadcastOp> {
   using ConvertTritonGPUOpToLLVMPattern<
@@ -1319,7 +1301,7 @@ public:
 
     RewritePatternSet patterns(context);
 
-    int numWarps = extractNumWarps(mod);
+    int numWarps = triton::gpu::TritonGPUDialect::getNumWarps(mod);
 
     auto axisAnalysis = runAxisAnalysis(mod);