[DebugInfo] Add support for __fp16, float, and double constants.

Summary:
Partial fix for PR26619.

Prior to this change, a DIGlobalVariable corresponding to a static
const was marked with an expression corresponding to its constant
value only if it is of integral type.  With this change, we now do the
same if it is of __fp16, float, or double type (that is,
floating-point types that do not exceed 64 bits in size, and hence are
supported easily by the existing LLVM machinery for creating constant
expressions in debug info).

Reviewers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27549

llvm-svn: 289094

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -3760,6 +3760,9 @@ void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD, const APValue &Init) {
   if (Init.isInt())
     InitExpr =
         DBuilder.createConstantValueExpression(Init.getInt().getExtValue());
+  else if (Init.isFloat() && CGM.getContext().getTypeSize(VD->getType()) <= 64)
+    InitExpr = DBuilder.createConstantValueExpression(
+        Init.getFloat().bitcastToAPInt().getZExtValue());
   GV.reset(DBuilder.createGlobalVariable(
       DContext, Name, StringRef(), Unit, getLineNumber(VD->getLocation()), Ty,
       true, InitExpr, getOrCreateStaticDataMemberDeclarationOrNull(VarD),

clang/test/CodeGen/debug-info-static-const-fp.c

@@ -0,0 +1,27 @@
+// RUN: %clang -emit-llvm -O0 -S -g %s -o - | FileCheck %s
+
+// Per PR26619, check that for referenced static const of floating-point type,
+// we emit its constant value in debug info.  NOTE that PR26619 is not yet fixed for long double.
+
+static const __fp16 hVal = 29/13.0f;            //    2.2307692307692307692     (2.23046875)
+
+static const float fVal = -147/17.0f;           //   -8.6470588235294117647     (-8.64705849)
+
+static const double dVal = 19637/7.0;           // 2805.2857142857142857        (2805.2857142857142)
+
+static const long double ldVal = 3/1234567.0L;  //    2.4300017739012949479e-06 (<optimized out>)
+
+int main() {
+  return hVal + fVal + dVal + ldVal;
+}
+
+// CHECK: !DIGlobalVariable(name: "hVal", {{.*}}, isLocal: true, isDefinition: true, expr: ![[HEXPR:[0-9]+]]
+// CHECK: ![[HEXPR]] = !DIExpression(DW_OP_constu, 16502, DW_OP_stack_value)
+
+// CHECK: !DIGlobalVariable(name: "fVal", {{.*}}, isLocal: true, isDefinition: true, expr: ![[FEXPR:[0-9]+]]
+// CHECK: ![[FEXPR]] = !DIExpression(DW_OP_constu, 3238681178, DW_OP_stack_value)
+
+// CHECK: !DIGlobalVariable(name: "dVal", {{.*}}, isLocal: true, isDefinition: true, expr: ![[DEXPR:[0-9]+]]
+// CHECK: ![[DEXPR]] = !DIExpression(DW_OP_constu, 4658387303597904457, DW_OP_stack_value)
+
+// CHECK: !DIGlobalVariable(name: "ldVal", {{.*}}, isLocal: true, isDefinition: true)