[CIR][Codegen] Support codegen for FP truncations. (#291)

Author: yugr

clang/lib/CIR/CodeGen/CIRGenBuilder.h

@@ -557,7 +557,9 @@ class CIRGenBuilderTy : public mlir::OpBuilder {
     llvm_unreachable("negation for the given type is NYI");
   }
 
-  mlir::Value createFPExt(mlir::Value v, mlir::Type destType) {
+  // TODO: split this to createFPExt/createFPTrunc when we have dedicated cast
+  // operations.
+  mlir::Value createFloatingCast(mlir::Value v, mlir::Type destType) {
     if (getIsFPConstrained())
       llvm_unreachable("constrainedfp NYI");
 

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -1670,11 +1670,8 @@ mlir::Value ScalarExprEmitter::buildScalarCast(
       return Builder.create<mlir::cir::CastOp>(
           Src.getLoc(), DstTy, mlir::cir::CastKind::float_to_int, Src);
     } else if (DstElementTy.isa<mlir::FloatType>()) {
-      auto FloatDstTy = DstTy.cast<mlir::FloatType>();
-      auto FloatSrcTy = SrcTy.cast<mlir::FloatType>();
-      if (FloatDstTy.getWidth() < FloatSrcTy.getWidth())
-        llvm_unreachable("NYI: narrowing floating-point cast");
-      return Builder.createFPExt(Src, DstTy);
+      // TODO: split this to createFPExt/createFPTrunc
+      return Builder.createFloatingCast(Src, DstTy);
     } else {
       llvm_unreachable("Unexpected destination type for scalar cast");
     }

clang/test/CIR/CodeGen/cast.cpp

@@ -17,7 +17,7 @@ unsigned char cxxstaticcast_0(unsigned int x) {
 // CHECK:  }
 
 
-int cStyleCasts_0(unsigned x1, int x2, float x3, short x4) {
+int cStyleCasts_0(unsigned x1, int x2, float x3, short x4, double x5) {
 // CHECK: cir.func @_{{.*}}cStyleCasts_0{{.*}}
 
   char a = (char)x1; // truncate
@@ -68,11 +68,14 @@ int cStyleCasts_0(unsigned x1, int x2, float x3, short x4) {
   unsigned fptoui = (unsigned)x3; // Floating point to unsigned integer
   // CHECK: %{{.+}} = cir.cast(float_to_int, %{{[0-9]+}} : f32), !u32i
 
-  bool x5 = (bool)x1; // No checking, because this isn't a cast.
+  bool ib = (bool)x1; // No checking, because this isn't a cast.
 
-  int bi = (int)x5; // bool to int
+  int bi = (int)ib; // bool to int
   // CHECK: %{{[0-9]+}} = cir.cast(bool_to_int, %{{[0-9]+}} : !cir.bool), !s32i
 
+  float dptofp = (float)x5;
+  // CHECK: %{{.+}} = cir.cast(floating, %{{[0-9]+}} : f64), f32
+
   return 0;
 }
 

clang/test/CIR/Lowering/cast.cir

@@ -10,7 +10,7 @@
 !u64i = !cir.int<u, 64>
 
 module {
-  cir.func @cStyleCasts(%arg0: !u32i, %arg1: !s32i, %arg2: f32) -> !s32i {
+  cir.func @cStyleCasts(%arg0: !u32i, %arg1: !s32i, %arg2: f32, %arg3: f64) -> !s32i {
   // CHECK: llvm.func @cStyleCasts
     %0 = cir.alloca !u32i, cir.ptr <!u32i>, ["x1", init] {alignment = 4 : i64}
     %1 = cir.alloca !s32i, cir.ptr <!s32i>, ["x2", init] {alignment = 4 : i64}
@@ -74,6 +74,8 @@ module {
     %28 = cir.cast(float_to_int, %arg2 : f32), !u32i
     // CHECK: %{{.+}} = llvm.fptoui %{{.+}} : f32 to i32
     %18 = cir.const(#cir.int<0> : !s32i) : !s32i
+    // CHECK: %{{.+}} = llvm.fptrunc %{{.+}} : f64 to f32
+    %34 = cir.cast(floating, %arg3 : f64), f32
 
     cir.store %18, %2 : !s32i, cir.ptr <!s32i>
     %19 = cir.load %2 : cir.ptr <!s32i>, !s32i